One document matched: draft-schaad-cose-alg-00.xml
<?xml version='1.0' encoding='ascii'?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
<?rfc toc="yes"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes"?>
<?rfc comments="yes"?>
<rfc ipr="trust200902" docName="draft-schaad-cose-alg-00" category="info" obsoletes="" updates="" submissionType="IETF" xml:lang="en">
<front>
<title>CBOR Encoded Message Syntax</title>
<author initials="J." surname="Schaad" fullname="Jim Schaad">
<organization>August Cellars</organization>
<address>
<email>ietf@augustcellars.com</email>
</address>
</author>
<date/>
<area>Security</area>
<workgroup>COSE Working Group</workgroup>
<abstract>
<t>More Alg and Headers for COSE. </t>
</abstract>
<note title="Contributing to this document">
<!--RFC EDITOR - Please remove this note before publishing -->
<t>The source for this draft is being maintained in GitHub. Suggested changes should be submitted as pull requests at <eref target="https://github.com/cose-wg/cose-algs"/>. Instructions are on that page as well. Editorial changes can be managed in GitHub, but any substantial issues need to be discussed on the COSE mailing list. </t>
</note>
</front>
<middle>
<section anchor="introduction" title="Introduction" toc="default">
<t>In the process of writing RFCXXXX <xref target="I-D.ietf-cose-msg" pageno="false" format="default"/> several items were removed from that ocument to be addressed at a later date. This document was created to address those items. </t>
<section anchor="requirements-terminology" title="Requirements Terminology" toc="default">
<!--NOTE FOR AUTHORS: We use the following terms in the document field - an entry in a CBOR array parameter - an element in a CBOR map (as oppose to 'member' which is frequently used in JSON label - the key of an element in a CBOR map. Unless otherwise separated from text, enclose with single quote marks value - the value of an element in a CBOR map -->
<t>The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “NOT RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in <xref target="RFC2119" pageno="false" format="default"/>. </t>
<t>When the words appear in lower case, their natural language meaning is used. </t>
</section>
<section anchor="cbor-grammar" title="CBOR Grammar" toc="default">
<t>There currently is no standard CBOR grammar available for use by specifications. We therefore describe the CBOR structures in prose. There is a version of a CBOR grammar in the CBOR Data Definition Language (CDDL) <xref target="I-D.greevenbosch-appsawg-cbor-cddl" pageno="false" format="default"/>. An informational version of the CBOR grammar that reflects what is in the prose can be found in <xref target="Grammar_Appendix" pageno="false" format="default"/>. CDDL has not been fixed, so this grammar may will only work with the version of CDDL at the time of publishing. </t>
<t>The document was developed by first working on the grammar and then developing the prose to go with it. An artifact of this is that the prose was written using the primitive type strings defined by early versions CDDL. In this specification the following primitive types are used: <list style="none"><t>bstr - byte string (major type 2).</t><t>int - an unsigned integer or a negative integer.</t><t>nil - a null value (tag 7.22).</t><t>nint - a negative integer (major type 1).</t><t>tstr - a UTF-8 text string (major type 3).</t><t>uint - an unsigned integer (major type 0).</t></list> </t>
<!--RFC EDITOR - Please make sure the following paragraphs have been removed. -->
<t>Text from here to start of next section to be removed </t>
<t>NOTE: For the purposes of review, we are currently interlacing the CDLL grammar into the text of document. This is being done for simplicity of comparision of the grammar againist the prose. The grammar will be removed to an appendix during WGLC. </t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork type="CDDL" xml:space="preserve" name="" align="left" alt="" width="" height="">
start = COSE_Untagged_Message / COSE_Tagged_Message / COSE_Key / COSE_KeySet
</artwork>
</figure>
</section>
<section title="Document Terminology" toc="default">
<t>In this document we use the following terminology: <cref source="JLS">I have not gone through the document to determine what needs to be here yet. We mostly want to grab terms which are used in unusual ways or are not generally understood. </cref> </t>
</section>
</section>
<section title="Signature Algorithms" toc="default">
<t>There are two basic signature algorithm structures that can be used. The first is the common signature with appendix. In this structure, the message content is processed and a signature is produced, the signature is called the appendix. This is the message structure used by our common algorithms such as ECDSA and RSASSA-PSS. (In fact the SSA in RSASSA-PSS stands for Signature Scheme with Appendix.) The basic structure becomes: </t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
signature = Sign(message content, key)
valid = Verification(message content, key, signature)
</artwork>
</figure>
<t>The second is a signature with message recovery. (An example of such an algorithm is <xref target="PVSig" pageno="false" format="default"/>.) In this structure, the message content is processed, but part of is included in the signature. Moving bytes of the message content into the signature allows for an effectively smaller signature, the signature size is still potentially large, but the message content is shrunk. This has implications for systems implementing these algoritms and for applications that use them. The first is that the message content is not fully available until after a signature has been validated. Until that point the part of the message contained inside of the signature is unrecoverable. The second is that the security analysis of the strength of the signature is very much based on the structure of the message content. Messages which are highly predictable require additional randomness to be supplied as part of the signature process, in the worst case it becomes the same as doing a signature with appendix. Thirdly, in the event that multple signatures are applied to a message, all of the signature algorithms are going to be required to consume the same number of bytes of message content. </t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
signature, message sent = Sign(message content, key)
valid, message content = Verification(message sent, key, signature)
</artwork>
</figure>
<t>At this time, only signatures with appendixes are defined for use with COSE, however considerable interest has been expressed in using a signature with message recovery algorithm due to the effective size reduction that is possible. Implementations will need to keep this in mind for later possible integration. </t>
<section title="RSASSA-PSS" toc="default">
<t>The RSASSA-PSS signature algorithm is defined in <xref target="RFC3447" pageno="false" format="default"/>. </t>
<t>The RSASSA-PSS signature algorithm is parametized with a hash function (h), a mask generation function (mgf) and a salt length (sLen). For this specification, the mask generation function is fixed to be MGF1 as defined in <xref target="RFC3447" pageno="false" format="default"/>. It has been recommended that the same hash function be used for hashing the data as well as in the mask generation function, for this specification we following this recommendation. The salt length is the same length as the hash function output. </t>
<t>Implementations need to check that the key type is 'RSA' when creating or verifying a signature. </t>
<t>The algorithms defined in this document can be found in <xref target="table-rsa-algs" pageno="false" format="default"/>. </t>
<texttable anchor="table-rsa-algs" title="RSASSA-PSS Algorithm Values" suppress-title="false" align="center" style="full">
<ttcol align="left">name</ttcol>
<ttcol align="left">value</ttcol>
<ttcol align="left">hash</ttcol>
<ttcol align="left">salt length</ttcol>
<ttcol align="left">description</ttcol>
<c>PS256</c>
<c>-26</c>
<c>SHA-256</c>
<c>32</c>
<c>RSASSA-PSS w/ SHA-256</c>
<c>PS384</c>
<c>-27</c>
<c>SHA-384</c>
<c>48</c>
<c>RSASSA-PSS w/ SHA-384</c>
<c>PS512</c>
<c>-28</c>
<c>SHA-512</c>
<c>64</c>
<c>RSASSA-PSS w/ SHA-512</c>
</texttable>
<section title="Security Considerations" anchor="RSASSA-PSS-considerations" toc="default">
<t>In addition to needing to worry about keys that are too small to provide the required security, there are issues with keys that are too large. Denial of service attacks have been mounted with overly large keys. This has the potential to consume resources with potentially bad keys. There are two reasonable ways to address this attack. First, a key should not be used for a cryptographic operation until it has been matched back to an authorized user. This approach means that no cryptography would be done except for authorized users. Second, applications can impose maximum as well as minimum length requirements on keys. This limits the resources consumed even if the matching is not performed until the cryptography has been done. </t>
<t>There is a theoretical hash substitution attack that can be mounted against RSASSA-PSS. However, the requirement that the same hash function be used consistently for all operations is an effective mitigation against it. Unlike ECDSA, hash functions are not truncated so that the full hash value is always signed. The internal padding structure of RSASSA-PSS means that one needs to have multiple collisions between the two hash functions in order to be successful in producing a forgery based on changing the hash function. This is highly unlikely. </t>
</section>
</section>
<section title="Edwards-curve Digital Signature Algorithms (EdDSA)" toc="default">
<t>Reference for these is <xref target="I-D.irtf-cfrg-eddsa" pageno="false" format="default"/>. </t>
<t>The algorithms defined in this document can be found in <xref target="table-eddsa-algs" pageno="false" format="default"/>. </t>
<texttable anchor="table-eddsa-algs" title="EdDSA Algorithm Values" suppress-title="false" align="center" style="full">
<ttcol align="left">name</ttcol>
<ttcol align="left">value</ttcol>
<ttcol align="left">description</ttcol>
<c>Ed25519</c>
<c>*</c>
<c>EdDSA for Curve 25591</c>
<c>Ed488</c>
<c>*</c>
<c>EdDSA for Curve 448</c>
</texttable>
</section>
</section>
<section title="Message Authentication (MAC) Algorithms" toc="default">
<t>Message Authentication Codes (MACs) provide data authentication and integrity protection. They provide either no or very limited data origination. (One cannot, for example, be used to prove the identity of the sender to a third party.) </t>
<t>MACs are designed in the same basic structure as signature with appendix algorithms. The message content is processed and an authentication code is produced, the authentication code is frequently called a tag. The basic structure becomes: </t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
tag = MAC_Create(message content, key)
valid = MAC_Verify(message content, key, tag)
</artwork>
</figure>
<t>MAC algorithms can be based on either a block cipher algorithm (i.e. AES-MAC) or a hash algorithm (i.e. HMAC). This document defines a MAC algorithm for each of these two constructions. </t>
</section>
<section title="Content Encryption Algorithms" toc="default">
<t>Content Encryption Algorithms provide data confidentialty for potentially large blocks of data using a symmetric key. They provide either no or very limited data origination. (One cannot, for example, be used to prove the identity of the sender to a third party.) The ability to provide data origination is linked to how the symmetric key is obtained. </t>
<t>We restrict the set of legal content encryption algorithms to those which support authentication both of the content and additional data. The encryption process will generate some type of authentication value, but that value may be either explicit or implicit in terms of the algorithm definition. For simplicity sake, the authentication code will normally be defined as being appended to the cipher text stream. The basic structure becomes: </t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
ciphertext = Encrypt(message content, key, additional data)
valid, message content = Decrypt(cipher text, key, additional data)
</artwork>
</figure>
<t>Most AEAD algorithms are logically defined as returning the message content only if the decryption is valid. Many but not all implementations will follow this convention. The message content MUST NOT be used if the decryption does not validate. </t>
<section title="ChaCha20 and Poly1305" toc="default">
<t>ChaCha20 and Poly1305 combined together is a new AEAD mode that is defined in <xref target="RFC7539" pageno="false" format="default"/>. This is a new algorithm defined to be a cipher which is not AES and thus would not suffer from any future weaknesses found in AES. These cryptographic functions are designed to be fast in software only implementations. </t>
<t>The ChaCha20/Poly1305 AEAD construction defined in <xref target="RFC7539" pageno="false" format="default"/> has no parameterization. It takes a 256-bit key and an a 96-bit nonce as well as the plain text and additional data as inputs and produces the cipher text as an option. We define one algorithm identifier for this algorithm in <xref target="Table-CHACHA" pageno="false" format="default"/>. </t>
<texttable title="Algorithm Value for AES-GCM" anchor="Table-CHACHA" suppress-title="false" align="center" style="full">
<ttcol align="left">name</ttcol>
<ttcol align="left">value</ttcol>
<ttcol align="left">description</ttcol>
<c>ChaCha20/Poly1305</c>
<c>11</c>
<c>ChaCha20/Poly1305 w/ 256-bit key</c>
</texttable>
<t>Keys may be obtained either from a key structure or from a recipient structure. If the key obtained from a key structure, the key type MUST be 'Symmetric'. Implementations creating and validating MAC values MUST validate that the key type, key length and algorithm are correct and appropriate for the entities involved. </t>
<section title="Security Considerations" toc="default">
<t>The pair of key, nonce MUST be unique for every invocation of the algorithm. Nonce counters are considered to be an acceptable way of ensuring that they are unique. </t>
</section>
</section>
</section>
<section title="Key Derivation Functions (KDF)" toc="default">
<t>Key Derivation Functions (KDFs) are used to take some secret value and generate a different one. The original secret values come in three basic flavors: <list style="symbols"><t>Secrets which are uniformly random: This is the type of secret which is created by a good random number generator.</t><t>Secrets which are not uniformly random: This is type of secret which is created by operations like key agreement.</t><t>Secrets which are not random: This is the type of secret that people generate for things like passwords.</t></list> </t>
<t>General KDF functions work well with the first type of secret, can do reasonable well with the second type of secret and generally do poorly with the last type of secret. None of the KDF functions in this section are designed to deal with the type of secrets that are used for passwords. Functions like PBSE2 <xref target="RFC2898" pageno="false" format="default"/> need to be used for that type of secret. </t>
<t>Many functions are going to handle the first two type of secrets differently. The KDF function defined in [HKDF] can use different underlying constructions if the secret is uniformly random than if the secret is not uniformly random. This is reflected in the set of algorithms defined for HKDF. </t>
<t>When using KDF functions, one component that is generally included is context information. Context information is used to allow for different keying information to be derived from the same secret. The use of context based keying material is considered to be a good security practice. This document defines a single context structure and a single KDF function. </t>
</section>
<section title="Recipient Algorithm Classes" anchor="key-management-algs" toc="default">
<t>Recipient algorithms can be defined into a number of different classes. COSE has the ability to support many classes of recipient algorithms. In this section, a number of classes are listed and then a set of algorithms are specified for each of the classes. The names of the recipient algorithm classes used here are the same as are defined in <xref target="RFC7517" pageno="false" format="default"/>. Other specifications use different terms for the recipient algorithm classes or do not support some of our recipient algorithm classes. </t>
<section title="Direct Encryption" toc="default">
<t>The direct encryption class algorithms share a secret between the sender and the recipient that is used either directly or after manipulation as the content key. When direct encryption mode is used, it MUST be the only mode used on the message. </t>
<t>The COSE_encrypt structure for the recipient is organized as follows: </t>
<t><list style="symbols"><t>The 'protected' field MUST be a zero length item if it is not used in the computation of the content key. </t><t>The 'alg' parameter MUST be present. </t><t>A parameter identifying the shared secret SHOULD be present. </t><t>The 'ciphertext' field MUST be a zero length item. </t><t>The 'recipients' field MUST be absent. </t></list> </t>
<section title="Direct Key with KDF" toc="default">
<t>These recipient algorithms take a common shared secret between the two parties and applies the HKDF function using the context structure defined in [CONTEXT] to transform the shared secret into the necessary key. Either the 'salt' parameter of HKDF or the partyU 'nonce' parameter of the context structure MUST be present. This parameter can be generated either randomly or deterministically, the requirement is that it be a unique value for the key pair in question. </t>
<t>If the salt/nonce value is generated randomly, then it is suggested that the length of the random value be the same length as the hash function underlying HKDF. While there is no way to guarantee that it will be unique, there is a high probability that it will be unique. If the salt/nonce value is generated deterministically, it can be guaranteed to be unique and thus there is no length requirement. </t>
<t>A new IV must be used if the same key is used in more than one message. The IV can be modified in a predictable manner, a random manner or an unpredictable manner. One unpredictable manner that can be used is to use the HKDF function to generate the IV. If HKDF is used for generating the IV, the algorithm identifier is set to "IV-GENERATION". </t>
<t>When these algorithms are used, the key type MUST be 'symmetric'. </t>
<t>The set of algorithms defined in this document can be found in <xref target="table-direct-kdf" pageno="false" format="default"/>. </t>
<texttable title="Direct Key" anchor="table-direct-kdf" suppress-title="false" align="center" style="full">
<ttcol align="left">name</ttcol>
<ttcol align="left">value</ttcol>
<ttcol align="left">KDF</ttcol>
<ttcol align="left">description</ttcol>
<c>direct+HKDF-SHA-256</c>
<c>*</c>
<c>HKDF SHA-256</c>
<c>Shared secret w/ HKDF and SHA-256</c>
<c>direct+HKDF-SHA-512</c>
<c>*</c>
<c>HKDF SHA-512</c>
<c>Shared secret w/ HKDF and SHA-512</c>
<c>direct+HKDF-AES-128</c>
<c>*</c>
<c>HKDF AES-MAC-128</c>
<c>Shared secret w/ AES-MAC 128-bit key</c>
<c>direct+HKDF-AES-256</c>
<c>*</c>
<c>HKDF AES-MAC-256</c>
<c>Shared secret w/ AES-MAC 256-bit key</c>
</texttable>
<section title="Security Considerations" toc="default">
<t>The shared secret need to have some method to be regularly updated over time. The shared secret is forming the basis of trust, although not used directly it should still be subject to scheduled rotation. </t>
</section>
</section>
</section>
<section title="Key Wrapping" toc="default">
<t>In key wrapping mode, the CEK is randomly generated and that key is then encrypted by a shared secret between the sender and the recipient. All of the currently defined key wrapping algorithms for JOSE (and thus for COSE) are AE algorithms. Key wrapping mode is considered to be superior to direct encryption if the system has any capability for doing random key generation. This is because the shared key is used to wrap random data rather than data has some degree of organization and may in fact be repeating the same content. </t>
<t>The COSE_encrypt structure for the recipient is organized as follows: </t>
<t><list style="symbols"><t>The 'protected' field MUST be absent if the key wrap algorithm is an AE algorithm. </t><t>The 'recipients' field is normally absent, but can be used. Applications MUST deal with a recipients field present, not being able to decrypt that recipient is an acceptable way of dealing with it. Failing to process the message is not an acceptable way of dealing with it. </t><t>The plain text to be encrypted is the key from next layer down (usually the content layer). </t><t>At a minimum, the 'unprotected' field MUST contain the 'alg' parameter and SHOULD contain a parameter identifying the shared secret. </t></list> </t>
</section>
<section title="Key Encryption" toc="default">
<t>Key Encryption mode is also called key transport mode in some standards. Key Encryption mode differs from Key Wrap mode in that it uses an asymmetric encryption algorithm rather than a symmetric encryption algorithm to protect the key. This document defines one Key Encryption mode algorithm. </t>
<t>When using a key encryption algorithm, the COSE_encrypt structure for the recipient is organized as follows: <list style="symbols"><t>The 'protected' field MUST be absent. </t><t>The plain text to be encrypted is the key from next layer down (usually the content layer). </t><t>At a minimum, the 'unprotected' field MUST contain the 'alg' parameter and SHOULD contain a parameter identifying the asymmetric key. </t></list> </t>
<section title="RSAES-OAEP" toc="default">
<t>RSAES-OAEP is an asymmetric key encryption algorithm. The defintion of RSAEA-OAEP can be find in Section 7.1 of <xref target="RFC3447" pageno="false" format="default"/>. The algorithm is parameterized using a masking generation function (mgf), a hash function (h) and encoding parameters (P). For the algorithm identifiers defined in this section: <list style="symbols"><t>mgf is always set to MFG1 from <xref target="RFC3447" pageno="false" format="default"/> and uses the same hash function as h.</t><t>P is always set to the empty octet string.</t></list> <xref target="table-RSA-OAEP" pageno="false" format="default"/> summarizes the rest of the values. </t>
<texttable anchor="table-RSA-OAEP" title="RSAES-OAEP Algorithm Values" suppress-title="false" align="center" style="full">
<ttcol align="left">name</ttcol>
<ttcol align="left">value</ttcol>
<ttcol align="left">hash</ttcol>
<ttcol align="left">description</ttcol>
<c>RSAES-OAEP w/SHA-256</c>
<c>-25</c>
<c>SHA-256</c>
<c>RSAES OAEP w/ SHA-256</c>
<c>RSAES-OAEP w/SHA-512</c>
<c>-26</c>
<c>SHA-512</c>
<c>RSAES OAEP w/ SHA-512</c>
</texttable>
<t>The key type MUST be 'RSA'. </t>
<section title="Security Considerations for RSAES-OAEP" toc="default">
<t>A key size of 2048 bits or larger MUST be used with these algorithms. This key size corresponds roughly to the same strength as provided by a 128-bit symmetric encryption algorithm. </t>
<t>It is highly recommended that checks on the key length be done before starting a decryption operation. One potential denial of service operation is to provide encrypted objects using either abnormally long or oddly sized RSA modulus values. Implementations SHOULD be able to encrypt and decrypt with modulus between 2048 and 16K bits in length. Applications can impose additional restrictions on the length of the modulus. </t>
</section>
</section>
</section>
<section title="Direct Key Agreement" toc="default">
<t>The 'direct key agreement' class of recipient algorithms uses a key agreement method to create a shared secret. A KDF is then applied to the shared secret to derive a key to be used in protecting the data. This key is normally used as a CEK or MAC key, but could be used for other purposes if more than two layers are in use (see [THREE-LAYER] <!--<xref target="three-layer"/> -->). </t>
<t>The most commonly used key agreement algorithm used is Diffie-Hellman, but other variants exist. Since COSE is designed for a store and forward environment rather than an on-line environment, many of the DH variants cannot be used as the receiver of the message cannot provide any key material. One side-effect of this is that perfect forward security is not achievable, a static key will always be used for the receiver of the COSE message. </t>
<t>Two variants of DH that are easily supported are: <list><t>- Ephemeral-Static DH: where the sender of the message creates a one time DH key and uses a static key for the recipient. The use of the ephemeral sender key means that no additional random input is needed as this is randomly generated for each message. </t><t>Static-Static DH: where a static key is used for both the sender and the recipient. The use of static keys allows for recipient to get a weak version of data origination for the message. When static-static key agreement is used, then some piece of unique data is require to ensure that a different key is created for each message </t></list> In this specification, both variants are specified. This has been done to provide the weak data origination option for use with MAC operations. </t>
<t>When direct key agreement mode is used, there MUST be only one recipient in the message. This method creates the key directly and that makes it difficult to mix with additional recipients. If multiple recipients are needed, then the version with key wrap needs to be used. </t>
<t>The COSE_encrypt structure for the recipient is organized as follows: </t>
<t><list style="symbols"><t>The 'protected' field MUST be absent. </t><t>At a minimum, the 'unprotected' field MUST contain the 'alg' parameter and SHOULD contain a parameter identifying the recipient's asymmetric key. </t><t>The 'unprotected' field MUST contain the 'epk' parameter. </t></list> </t>
<section title="ECDH" toc="default">
<t>The basic mathematics for Elliptic Curve Diffie-Hellman can be found in <xref target="RFC6090" pageno="false" format="default"/>. Two new curves have been defined in <xref target="I-D.irtf-cfrg-curves" pageno="false" format="default"/>. </t>
<t>ECDH is parameterized by the following: <list style="symbols"><t>Curve Type/Curve: The curve selected controls not only the size of the shared secret, but the mathematics for computing the shared secret. The curve selected also controls how a point in the curve is represented and what happens for the identity points on the curve. In this specification we allow for a number of different curves to be used. The curves are defined in <xref target="table-ec-curves" pageno="false" format="default"/>. <vspace blankLines="0"/> Since the only the math is changed by changing the curve, the curve is not fixed for any of the algorithm identifiers we define, instead it is defined by the points used. </t><t>Ephemeral-static or static-static: The key agreement process may be done using either a static or an ephemeral key at the senders side. When using ephemeral keys, the sender MUST generate a new ephemeral key for every key agreement operation. The ephemeral key is placed in in the 'ephemeral key' parameter and MUST be present for all algorithm identifiers which use ephemeral keys. When using static keys, the sender MUST either generate a new random value placed in either in the KDF parameters or the context structure. For the KDF functions used, this means either in the 'salt' parameter for HKDF [HKDF_Alg_Params]) or in in the 'PartyU nonce' parameter for the context struture ([KDF_Context_Alg_Params]) MUST be present. (Both may be present if desired.) The value in the parameter MUST be unique for the key pair being used. It is acceptable to use a global counter which is incremented for every static-static operation and use the resulting value. When using static keys, the static key needs to be identified to the recipient. The static key can be identified either by providing the key ('static key') or by providing a key identifier for the static key ('static key id'). Both of these parameters are defined in <xref target="table-ecdh-es-parameter-table" pageno="false" format="default"/> </t><t>Key derivation algorithm: The result of an ECDH key agreement process does not provide a uniformly random secret, as such it needs to be run through a KDF in order to produce a usable key. Processing the secret through a KDF also allows for the introduction of both context material, how the key is going to be used, and one time material in the even to of a static-static key agreement. </t><t>Key Wrap algorithm: The key wrap algorithm can be 'none' if the result of the KDF is going to be used as the key directly. This option, along with static-static, should be used if knowledge about the sender is desired. If 'none' is used then the content layer encryption algorithm size is value fed to the context structure. Support is also provided for any of the key wrap algorithms defined in section [KEY_WRAP_ALGS]. If one of these options is used, the input key size to the key wrap algorithm is the value fed into the context structure as the key size. </t></list> </t>
<t>The set of algorithms direct ECDH defined in this document are found in <xref target="table-ecdh-es-table" pageno="false" format="default"/>. </t>
<texttable title="ECDH Algorithm Values" anchor="table-ecdh-es-table" suppress-title="false" align="center" style="full">
<ttcol align="left">name</ttcol>
<ttcol align="left">value</ttcol>
<ttcol align="left">KDF</ttcol>
<ttcol align="left">Ephemeral-Static</ttcol>
<ttcol align="left">Key Wrap</ttcol>
<ttcol align="left">description</ttcol>
<c>ECDH-ES + HKDF-256</c>
<c>50</c>
<c>HKDF - SHA-256</c>
<c>yes</c>
<c>none</c>
<c>ECDH ES w/ HKDF - generate key directly</c>
<c>ECDH-ES + HKDF-512</c>
<c>51</c>
<c>HKDF - SHA-256</c>
<c>yes</c>
<c>none</c>
<c>ECDH ES w/ HKDF - generate key directly</c>
<c>ECDH-SS + HKDF-256</c>
<c>52</c>
<c>HKDF - SHA-256</c>
<c>no</c>
<c>none</c>
<c>ECDH ES w/ HKDF - generate key directly</c>
<c>ECDH-SS + HKDF-512</c>
<c>53</c>
<c>HKDF - SHA-256</c>
<c>no</c>
<c>none</c>
<c>ECDH ES w/ HKDF - generate key directly</c>
<c>ECDH-ES+A128KW</c>
<c>54</c>
<c>HKDF - SHA-256</c>
<c>yes</c>
<c>A128KW</c>
<c>ECDH ES w/ Concat KDF and AES Key wrap w/ 128 bit key</c>
<c>ECDH-ES+A192KW</c>
<c>55</c>
<c>HKDF - SHA-256</c>
<c>yes</c>
<c>A192KW</c>
<c>ECDH ES w/ Concat KDF and AES Key wrap w/ 192 bit key</c>
<c>ECDH-ES+A256KW</c>
<c>56</c>
<c>HKDF - SHA-256</c>
<c>yes</c>
<c>A256KW</c>
<c>ECDH ES w/ Concat KDF and AES Key wrap w/ 256 bit key</c>
<c>ECDH-SS+A128KW</c>
<c>57</c>
<c>HKDF - SHA-256</c>
<c>no</c>
<c>A128KW</c>
<c>ECDH SS w/ Concat KDF and AES Key wrap w/ 128 bit key</c>
<c>ECDH-SS+A192KW</c>
<c>58</c>
<c>HKDF - SHA-256</c>
<c>no</c>
<c>A192KW</c>
<c>ECDH SS w/ Concat KDF and AES Key wrap w/ 192 bit key</c>
<c>ECDH-SS+A256KW</c>
<c>59</c>
<c>HKDF - SHA-256</c>
<c>no</c>
<c>A256KW</c>
<c>ECDH SS w/ Concat KDF and AES Key wrap w/ 256 bit key</c>
</texttable>
<texttable title="ECDH Algorithm Parameters" anchor="table-ecdh-es-parameter-table" suppress-title="false" align="center" style="full">
<ttcol align="left">name</ttcol>
<ttcol align="left">label</ttcol>
<ttcol align="left">type</ttcol>
<ttcol align="left">algorithm</ttcol>
<ttcol align="left">description</ttcol>
<c>ephemeral key</c>
<c>-1</c>
<c>COSE_Key</c>
<c>ECDH-ES</c>
<c>Ephemeral Public key for the sender</c>
<c>static key</c>
<c>-2</c>
<c>COSE_Key</c>
<c>ECDH-ES</c>
<c>Static Public key for the sender</c>
<c>static key id </c>
<c>-3</c>
<c>bstr</c>
<c>ECDH-SS</c>
<c>Static Public key identifier for the sender</c>
</texttable>
<t>This document defines these algorithms to be used with the curves P-256, P-384, P-521, X25519 and X448. Implementations MUST verify that the key type and curve are correct, different curves are restricted to different key types. Implementations MUST verify that the curve and algorithm are appropriate for the entities involved. </t>
</section>
</section>
<section title="Key Agreement with KDF" anchor="ECDH-Direct" toc="default">
<t>Key Agreement with Key Wrapping uses a randomly generated CEK. The CEK is then encrypted using a Key Wrapping algorithm and a key derived from the shared secret computed by the key agreement algorithm. </t>
<t>The COSE_encrypt structure for the recipient is organized as follows: </t>
<t><list style="symbols"><t>The 'protected' field is fed into the KDF context structure. </t><t>The plain text to be encrypted is the key from next layer down (usually the content layer). </t><t>The 'alg' parameter MUST be present in the layer. </t><t>A parameter identifying the recipient's key SHOULD be present. A parameter identifying the senders key SHOULD be present. </t></list> </t>
<section title="ECDH" toc="default">
<t>These algorithms are defined in <xref target="table-ecdh-es-table" pageno="false" format="default"/>. </t>
</section>
</section>
<section title="Password" toc="default">
<t><cref source="JLS">Do we want/need to support this? JOSE did it mainly to support the encryption of private keys. </cref> </t>
<section title="PBES2" toc="default">
<texttable title="" suppress-title="false" align="center" style="full">
<ttcol align="left">name</ttcol>
<ttcol align="left">value</ttcol>
<ttcol align="left">description</ttcol>
<c>PBES2-HS256+A128KW</c>
<c>*</c>
<c>PBES2 w/ HMAC SHA-256 and AES Key wrap w/ 128 bit key</c>
<c>PBES2-HS384+A192KW</c>
<c>*</c>
<c>PBES2 w/ HMAC SHA-384 and AES Key wrap w/ 192 bit key</c>
<c>PBES2-HS512+A256KW</c>
<c>*</c>
<c>PBES2 w/ HMAC SHA-512 and AES Key wrap w/ 256 bit key</c>
</texttable>
</section>
</section>
</section>
<section title="Keys" anchor="Key-specific-labels" toc="default">
<t>The COSE_Key object defines a way to hold a single key object, it is still required that the members of individual key types be defined. This section of the document is where we define an initial set of members for specific key types. </t>
<t>For each of the key types, we define both public and private members. The public members are what is transmitted to others for their usage. We define private members mainly for the purpose of archival of keys by individuals. However, there are some circumstances where private keys may be distributed by various entities in a protocol. Examples include: Entities which have poor random number generation. Centralized key creation for multi-cast type operations. Protocols where a shared secret is used as a bearer token for authorization purposes. </t>
<t>Key types are identified by the 'kty' member of the COSE_Key object. In this document we define four values for the member. </t>
<texttable title="Key Type Values" anchor="table_key_types" suppress-title="false" align="center" style="full">
<ttcol align="left">name</ttcol>
<ttcol align="left">value</ttcol>
<ttcol align="left">description</ttcol>
<c>EC1</c>
<c>1</c>
<c>Elliptic Curve Keys w/ X Coordinate only</c>
<c>RSA</c>
<c>3</c>
<c>RSA Keys</c>
</texttable>
<section title="Elliptic Curve Keys" toc="default">
<t>Two different key structures are being defined for Elliptic Curve keys. One version uses both an x and a y coordinate, potentially with point compression. This is the traditional EC point representation that is used in <xref target="RFC5480" pageno="false" format="default"/>. The other version uses only the x coordinate as the y coordinate is either to be recomputed or not needed for the key agreement operation. An example of this is Curve25519 <xref target="I-D.irtf-cfrg-curves" pageno="false" format="default"/>. <cref source="Ilari">Check to see what the curves are renamed to during final publishing. It appears to be X25519 now. </cref> </t>
<texttable title="EC Curves" anchor="table-ec-curves" suppress-title="false" align="center" style="full">
<ttcol align="left">name</ttcol>
<ttcol align="left">key type</ttcol>
<ttcol align="left">value</ttcol>
<ttcol align="left">description</ttcol>
<c>Curve25519</c>
<c>EC1</c>
<c>1</c>
<c>Curve 25519</c>
<c>Curve448</c>
<c>EC1</c>
<c>2</c>
<c>Curve 448</c>
</texttable>
<section title="Single Coordinate Curves" anchor="EC1-Keys" toc="default">
<t>One class of Elliptic Curve mathematics allows for a point to be completely defined using the curve and the x coordinate of the point on the curve. The two curves that are initially setup to use is point format are Curve 25519 and Curve 448 which are defined in <xref target="I-D.irtf-cfrg-curves" pageno="false" format="default"/>. </t>
<t>For EC keys with only the x coordinates, the 'kty' member is set to 1 (EC1). The key parameters defined in this section are summarized in <xref target="table-ec1-keys" pageno="false" format="default"/>. The members that are defined for this key type are: <list style="hanging"><t hangText="crv">contains an identifier of the curve to be used with the key. <cref source="JLS">Do we create a registry for curves? Is is the same registry for both EC1 and EC2? </cref> The curves defined in this document for this key type can be found in <xref target="table-ec-curves" pageno="false" format="default"/>. Other curves may be registered in the future and private curves can be used as well. </t><t hangText="x">contains the x coordinate for the EC point. The octet string represents a little-endian encoding of x. </t><t hangText="d">contains the private key. </t></list> </t>
<t>For public keys, it is REQUIRED that 'crv' and 'x' be present in the structure. For private keys, it is REQUIRED that 'crv' and 'd' be present in the structure. For private keys, it is RECOMMENDED that 'x' also be present, but it can be recomputed from the required elements and omitting it saves on space. </t>
<texttable title="EC Key Parameters" anchor="table-ec1-keys" suppress-title="false" align="center" style="full">
<ttcol align="left">name</ttcol>
<ttcol align="left">key type</ttcol>
<ttcol align="left">value</ttcol>
<ttcol align="left">type</ttcol>
<ttcol align="left">description</ttcol>
<c>crv</c>
<c>1</c>
<c>-1</c>
<c>int / tstr</c>
<c>EC Curve identifier - Taken from the COSE General Registry</c>
<c>x</c>
<c>1</c>
<c>-2</c>
<c>bstr</c>
<c>X Coordinate</c>
<c>d</c>
<c>1</c>
<c>-4</c>
<c>bstr</c>
<c>Private key</c>
</texttable>
</section>
</section>
<section title="RSA Keys" toc="default">
<t>This document defines a key structure for both the public and private halves of RSA keys. Together, an RSA public key and an RSA private key form an RSA key pair. <cref source="JLS">Looking at the CBOR specification, the bstr that we are looking in our table below should most likely be specified as big numbers rather than as binary strings. This means that we would use the tag 6.2 instead. From my reading of the specification, there is no difference in the encoded size of the resulting output. The specification of bignum does explicitly allow for integers encoded with leading zeros. </cref> </t>
<t>The document also provides support for the so-called "multi-prime" RSA where the modulus may have more than two prime factors. The benefit of multi-prime RSA is lower computational cost for the decryption and signature primitives. For a discussion on how multi-prime affects the security of RSA crypto-systems, the reader is referred to <xref target="MultiPrimeRSA" pageno="false" format="default"/>. </t>
<t>This document follows the naming convention of <xref target="RFC3447" pageno="false" format="default"/> for the naming of the fields of an RSA public or private key. The table <xref target="table-rsa-keys" pageno="false" format="default"/> provides a summary of the label values and the types associated with each of those labels. The requirements for fields for RSA keys are as follows: <list style="symbols"><t>For all keys, 'kty' MUST be present and MUST have a value of 3. </t><t>For public keys, the fields 'n' and 'e' MUST be present. All other fields defined in <xref target="table-rsa-keys" pageno="false" format="default"/> MUST be absent. </t><t>For private keys with two primes, the fields 'other', 'r_i', 'd_i' and 't_i' MUST be absent, all other fields MUST be present. </t><t>For private keys with more than two primes, all fields MUST be present. For the third to nth primes, each of the primes is represented as a map containing the fields 'r_i', 'd_i' and 't_i'. The field 'other' is an array of those maps. </t></list> </t>
<texttable title="RSA Key Parameters" anchor="table-rsa-keys" suppress-title="false" align="center" style="full">
<ttcol align="left">name</ttcol>
<ttcol align="left">key type</ttcol>
<ttcol align="left">value</ttcol>
<ttcol align="left">type</ttcol>
<ttcol align="left">description</ttcol>
<c>n</c>
<c>3</c>
<c>-1</c>
<c>bstr</c>
<c>Modulus Parameter</c>
<c>e</c>
<c>3</c>
<c>-2</c>
<c>int</c>
<c>Exponent Parameter</c>
<c>d</c>
<c>3</c>
<c>-3</c>
<c>bstr</c>
<c>Private Exponent Parameter</c>
<c>p</c>
<c>3</c>
<c>-4</c>
<c>bstr</c>
<c>First Prime Factor</c>
<c>q</c>
<c>3</c>
<c>-5</c>
<c>bstr</c>
<c>Second Prime Factor</c>
<c>dP</c>
<c>3</c>
<c>-6</c>
<c>bstr</c>
<c>First Factor CRT Exponent</c>
<c>dQ</c>
<c>3</c>
<c>-7</c>
<c>bstr</c>
<c>Second Factor CRT Exponent</c>
<c>qInv</c>
<c>3</c>
<c>-8</c>
<c>bstr</c>
<c>First CRT Coefficient</c>
<c>other</c>
<c>3</c>
<c>-9</c>
<c>array</c>
<c>Other Primes Info</c>
<c>r_i</c>
<c>3</c>
<c>-10</c>
<c>bstr</c>
<c>i-th factor, Prime Factor</c>
<c>d_i</c>
<c>3</c>
<c>-11</c>
<c>bstr</c>
<c>i-th factor, Factor CRT Exponent</c>
<c>t_i</c>
<c>3</c>
<c>-12</c>
<c>bstr</c>
<c>i-th factor, Factor CRT Coefficient</c>
</texttable>
</section>
</section>
<section anchor="iana-considerations" title="IANA Considerations" toc="default">
<section anchor="cose-header-key-table" title="COSE Header Parameter Registry" toc="default">
<t>There are currently no registration requests here </t>
</section>
<section anchor="IANA-Alg-Registry" title="COSE Header Algorithm Label Table" toc="default">
<t>It is requested that IANA create a new registry entitled “COSE Header Algorithm Labels”. </t>
<t>The columns of the registry are: <list style="hanging"><t hangText="name">The name is present to make it easier to refer to and discuss the registration entry. The value is not used in the protocol. </t><t hangText="algorithm">The algorithm(s) that this registry entry is used for. This value is taken from the “COSE Algorithm Value” registry. Multiple algorithms can be specified in this entry. For the table, the algorithm, label pair MUST be unique. </t><t hangText="label">This is the value used for the label. The label is an integer in the range of -1 to -65536. </t><t hangText="value">This contains the CBOR type for the value portion of the label. </t><t hangText="value registry">This contains a pointer to the registry used to contain values where the set is limited. </t><t hangText="description">This contains a brief description of the header field. </t><t hangText="specification">This contains a pointer to the specification defining the header field (where public). </t></list> </t>
<t>The initial contents of the registry can be found in: <xref target="table-ecdh-es-parameter-table" pageno="false" format="default"/>. The specification column for all rows in that table should be this document. </t>
</section>
<section anchor="cose-algorithm-registry" title="COSE Algorithm Registry" toc="default">
<t>It is requested that IANA create a new registry entitled “COSE Algorithm Registry”. </t>
<t><list style="hanging"><t hangText="The columns of the registry are:"></t><t hangText="value">The value to be used to identify this algorithm. Algorithm values MUST be unique. The value can be a positive integer, a negative integer or a string. Integer values between 0 and 255 and strings of length 1 are designated as Standards Track Document required. Integer values from 256 to 65535 and strings of length 2 are designated as Specification Required. Integer values of greater than 65535 and strings of length greater than 2 are designated as first come first server. Integer values in the range -1 to -65536 are delegated to the “COSE Header Algorithm Label” registry. Integer values beyond -65536 are marked as private use. </t><t hangText="description">A short description of the algorithm. </t><t hangText="specification">A document where the algorithm is defined (if publicly available). </t></list> </t>
<t>The initial contents of the registry can be found in the following: <xref target="Table-CHACHA" pageno="false" format="default"/>, <xref target="table-rsa-algs" pageno="false" format="default"/>, <xref target="table-direct-kdf" pageno="false" format="default"/>, <xref target="table-RSA-OAEP" pageno="false" format="default"/>, <xref target="table-ecdh-es-table" pageno="false" format="default"/>. The specification column for all rows in that table should be this document. </t>
</section>
<section anchor="cose-key-map-registry" title="COSE Key Common Parameter Registry" toc="default">
<t>There are currently no registration tasks inthis section. </t>
</section>
<section anchor="cose-key-parameter-registry" title="COSE Key Type Parameter Registry" toc="default">
<t>It is requested that IANA create a new registry “COSE Key Type Parameters”. </t>
<t>The columns of the table are: </t>
<t><list style="hanging"><t hangText="key type">This field contains a descriptive string of a key type. This should be a value that is in the COSE General Values table and is placed in the 'kty' field of a COSE Key structure. </t><t hangText="name">This is a descriptive name that enables easier reference to the item. It is not used in the encoding. </t><t hangText="label">The label is to be unique for every value of key type. The range of values is from -256 to -1. Labels are expected to be reused for different keys. </t><t hangText="CBOR type">This field contains the CBOR type for the field </t><t hangText="description">This field contains a brief description for the field </t><t hangText="specification">This contains a pointer to the public specification for the field if one exists </t></list> </t>
<t>This registry will be initially populated by the values in <xref target="table-ec1-keys" pageno="false" format="default"/>, and <xref target="table-rsa-keys" pageno="false" format="default"/>. The specification column for all of these entries will be this document. </t>
</section>
<section anchor="cose-curve-registry" title="COSE Elliptic Curve Registry" toc="default">
<t>It is requested that IANA create a new registry “COSE Elliptic Curve Parameters”. </t>
<t>The columns of the table are: </t>
<t><list style="hanging"><t hangText="name">This is a descriptive name that enables easier reference to the item. It is not used in the encoding. </t><t hangText="value">This is the value used to identify the curve. These values MUST be unique. The integer values from -256 to 255 are designated as Standards Track Document Required. The the integer values from 256 to 65535 and -65536 to -257 are designated as Specification Required. Integer values over 65535 are designated as first come first serve. Integer values less than -65536 are marked as private use. </t><t hangText="key type">This designates the key type(s) that can be used with this curve. </t><t hangText="description">This field contains a brief description of the curve. </t><t hangText="specification">This contains a pointer to the public specification for the curve if one exists. </t></list> </t>
<t>This registry will be initially populated by the values in <xref target="table_key_types" pageno="false" format="default"/>. The specification column for all of these entries will be this document. </t>
</section>
</section>
<section anchor="security-considerations" title="Security Considerations" toc="default">
<t>There are security considerations: </t>
<t><list style="numbers"><t>Protect private keys </t><t>MAC messages with more than one recipient means one cannot figure out who sent the message </t><t>Use of direct key with other recipient structures hands the key to other recipients. </t><t>Use of direct ECDH direct encryption is easy for people to leak information on if there are other recipients in the message. </t><t>Considerations about protected vs unprotected header fields. </t><t>Need to verify that: 1) the kty field of the key matches the key and algorithm being used. 2) that the kty field needs to be included in the trust decision as well as the other key fields. 3) that the algorithm be included in the trust decision. </t></list> </t>
</section>
</middle>
<back>
<references title="Normative References"><reference anchor="RFC2119"><front><title abbrev="RFC Key Words">Key words for use in RFCs to Indicate Requirement Levels</title><author initials="S." surname="Bradner" fullname="Scott Bradner"><organization>Harvard University</organization><address><postal><street>1350 Mass. Ave.</street><street>Cambridge</street><street>MA 02138</street></postal><phone>- +1 617 495 3864</phone><email>sob@harvard.edu</email></address></author><date year="1997" month="March"/><area>General</area><keyword>keyword</keyword><abstract><t>In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. Authors who follow these guidelines should incorporate this phrase near the beginning of their document: <list><t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. </t></list></t><t>Note that the force of these words is modified by the requirement level of the document in which they are used. </t></abstract></front><seriesInfo name="BCP" value="14"/><seriesInfo name="RFC" value="2119"/><format type="TXT" octets="4723" target="http://www.rfc-editor.org/rfc/rfc2119.txt"/><format type="HTML" octets="17970" target="http://xml.resource.org/public/rfc/html/rfc2119.html"/><format type="XML" octets="5777" target="http://xml.resource.org/public/rfc/xml/rfc2119.xml"/></reference> <reference anchor="RFC7049"><front><title>Concise Binary Object Representation (CBOR)</title><author initials="C." surname="Bormann" fullname="C. Bormann"><organization/></author><author initials="P." surname="Hoffman" fullname="P. Hoffman"><organization/></author><date year="2013" month="October"/><abstract><t>The Concise Binary Object Representation (CBOR) is a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation. These design goals make it different from earlier binary serializations such as ASN.1 and MessagePack.</t></abstract></front><seriesInfo name="RFC" value="7049"/><format type="TXT" octets="134062" target="http://www.rfc-editor.org/rfc/rfc7049.txt"/></reference> </references>
<references title="Informative References"><reference anchor="I-D.greevenbosch-appsawg-cbor-cddl"><front><title>CBOR data definition language: a notational convention to express CBOR data structures.</title><author initials="C" surname="Vigano" fullname="Christoph Vigano"><organization/></author><author initials="H" surname="Birkholz" fullname="Henk Birkholz"><organization/></author><author initials="R" surname="Sun" fullname="Ruinan Sun"><organization/></author><date month="March" day="9" year="2015"/><abstract><t>This document proposes a notational convention to express CBOR data structures (RFC 7049). Its main goal is to provide an easy and unambiguous way to express structures for protocol messages and data formats that use CBOR.</t></abstract></front><seriesInfo name="Internet-Draft" value="draft-greevenbosch-appsawg-cbor-cddl-05"/><format type="TXT" target="http://www.ietf.org/internet-drafts/draft-greevenbosch-appsawg-cbor-cddl-05.txt"/></reference> <!--&CBCMAC; --><reference anchor="RFC2104"><front><title abbrev="HMAC">HMAC: Keyed-Hashing for Message Authentication</title><author initials="H." surname="Krawczyk" fullname="Hugo Krawczyk"><organization>IBM, T.J. Watson Research Center</organization><address><postal><street>P.O.Box 704</street><city>Yorktown Heights</city><region>NY</region><code>10598</code><country>US</country></postal><email>hugo@watson.ibm.com</email></address></author><author initials="M." surname="Bellare" fullname="Mihir Bellare"><organization>University of California at San Diego, Dept of Computer Science and Engineering</organization><address><postal><street>9500 Gilman Drive</street><street>Mail Code 0114</street><city>La Jolla</city><region>CA</region><code>92093</code><country>US</country></postal><email>mihir@cs.ucsd.edu</email></address></author><author initials="R." surname="Canetti" fullname="Ran Canetti"><organization>IBM T.J. Watson Research Center</organization><address><postal><street>P.O.Box 704</street><city>Yorktown Heights</city><region>NY</region><code>10598</code><country>US</country></postal><email>canetti@watson.ibm.com</email></address></author><date year="1997" month="February"/><abstract><t>This document describes HMAC, a mechanism for message authentication using cryptographic hash functions. HMAC can be used with any iterative cryptographic hash function, e.g., MD5, SHA-1, in combination with a secret shared key. The cryptographic strength of HMAC depends on the properties of the underlying hash function.</t></abstract></front><seriesInfo name="RFC" value="2104"/><format type="TXT" octets="22297" target="http://www.rfc-editor.org/rfc/rfc2104.txt"/></reference> <reference anchor="RFC2633"><front><title>S/MIME Version 3 Message Specification</title><author initials="B." surname="Ramsdell" fullname="Blake Ramsdell"><organization>Worldtalk</organization><address><postal><street>17720 NE 65th Street</street><street>Suite 201</street><city>Redmond</city><region>WA</region><code>98052</code><country>US</country></postal><phone>+1 425 376 0225</phone><email>blaker@deming.com</email></address></author><date year="1999" month="June"/></front><seriesInfo name="RFC" value="2633"/><format type="TXT" octets="67870" target="http://www.rfc-editor.org/rfc/rfc2633.txt"/></reference> <reference anchor="RFC2898" target="http://www.rfc-editor.org/info/rfc2898"><front><title>PKCS #5: Password-Based Cryptography Specification Version 2.0</title><author initials="B." surname="Kaliski" fullname="B. Kaliski"><organization/></author><date year="2000" month="September"/><abstract><t>This document provides recommendations for the implementation of password-based cryptography, covering key derivation functions, encryption schemes, message-authentication schemes, and ASN.1 syntax identifying the techniques. This memo provides information for the Internet community.</t></abstract></front><seriesInfo name="RFC" value="2898"/><seriesInfo name="DOI" value="10.17487/RFC2898"/></reference> <reference anchor="RFC3394"><front><title>Advanced Encryption Standard (AES) Key Wrap Algorithm</title><author initials="J." surname="Schaad" fullname="J. Schaad"><organization/></author><author initials="R." surname="Housley" fullname="R. Housley"><organization/></author><date year="2002" month="September"/></front><seriesInfo name="RFC" value="3394"/><format type="TXT" octets="73072" target="http://www.rfc-editor.org/rfc/rfc3394.txt"/></reference> <reference anchor="RFC3447"><front><title>Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1</title><author initials="J." surname="Jonsson" fullname="J. Jonsson"><organization/></author><author initials="B." surname="Kaliski" fullname="B. Kaliski"><organization/></author><date year="2003" month="February"/><abstract><t>This memo represents a republication of PKCS #1 v2.1 from RSA Laboratories' Public-Key Cryptography Standards (PKCS) series, and change control is retained within the PKCS process. The body of this document is taken directly from the PKCS #1 v2.1 document, with certain corrections made during the publication process. This memo provides information for the Internet community.</t></abstract></front><seriesInfo name="RFC" value="3447"/><format type="TXT" octets="143173" target="http://www.rfc-editor.org/rfc/rfc3447.txt"/></reference> <reference anchor="RFC3610"><front><title>Counter with CBC-MAC (CCM)</title><author initials="D." surname="Whiting" fullname="D. Whiting"><organization/></author><author initials="R." surname="Housley" fullname="R. Housley"><organization/></author><author initials="N." surname="Ferguson" fullname="N. Ferguson"><organization/></author><date year="2003" month="September"/><abstract><t>Counter with CBC-MAC (CCM) is a generic authenticated encryption block cipher mode. CCM is defined for use with 128-bit block ciphers, such as the Advanced Encryption Standard (AES).</t></abstract></front><seriesInfo name="RFC" value="3610"/><format type="TXT" octets="64509" target="http://www.rfc-editor.org/rfc/rfc3610.txt"/></reference> <reference anchor="RFC4231"><front><title>Identifiers and Test Vectors for HMAC-SHA-224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512</title><author initials="M." surname="Nystrom" fullname="M. Nystrom"><organization/></author><date year="2005" month="December"/><abstract><t>This document provides test vectors for the HMAC-SHA-224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512 message authentication schemes. It also provides ASN.1 object identifiers and Uniform Resource Identifiers (URIs) to identify use of these schemes in protocols. The test vectors provided in this document may be used for conformance testing. [STANDARDS-TRACK]</t></abstract></front><seriesInfo name="RFC" value="4231"/><format type="TXT" octets="17725" target="http://www.rfc-editor.org/rfc/rfc4231.txt"/></reference> <reference anchor="RFC4262"><front><title>X.509 Certificate Extension for Secure/Multipurpose Internet Mail Extensions (S/MIME) Capabilities</title><author initials="S." surname="Santesson" fullname="S. Santesson"><organization/></author><date year="2005" month="December"/><abstract><t>This document defines a certificate extension for inclusion of Secure/Multipurpose Internet Mail Extensions (S/MIME) Capabilities in X.509 public key certificates, as defined by RFC 3280. This certificate extension provides an optional method to indicate the cryptographic capabilities of an entity as a complement to the S/MIME Capabilities signed attribute in S/MIME messages according to RFC 3851. [STANDARDS-TRACK]</t></abstract></front><seriesInfo name="RFC" value="4262"/><format type="TXT" octets="9801" target="http://www.rfc-editor.org/rfc/rfc4262.txt"/></reference> <reference anchor="RFC5480"><front><title>Elliptic Curve Cryptography Subject Public Key Information</title><author initials="S." surname="Turner" fullname="S. Turner"><organization/></author><author initials="D." surname="Brown" fullname="D. Brown"><organization/></author><author initials="K." surname="Yiu" fullname="K. Yiu"><organization/></author><author initials="R." surname="Housley" fullname="R. Housley"><organization/></author><author initials="T." surname="Polk" fullname="T. Polk"><organization/></author><date year="2009" month="March"/><abstract><t>This document specifies the syntax and semantics for the Subject Public Key Information field in certificates that support Elliptic Curve Cryptography. This document updates Sections 2.3.5 and 5, and the ASN.1 module of "Algorithms and Identifiers for the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 3279. [STANDARDS-TRACK]</t></abstract></front><seriesInfo name="RFC" value="5480"/><format type="TXT" octets="36209" target="http://www.rfc-editor.org/rfc/rfc5480.txt"/></reference> <reference anchor="RFC5652"><front><title>Cryptographic Message Syntax (CMS)</title><author initials="R." surname="Housley" fullname="R. Housley"><organization/></author><date year="2009" month="September"/><abstract><t>This document describes the Cryptographic Message Syntax (CMS). This syntax is used to digitally sign, digest, authenticate, or encrypt arbitrary message content. [STANDARDS-TRACK]</t></abstract></front><seriesInfo name="STD" value="70"/><seriesInfo name="RFC" value="5652"/><format type="TXT" octets="126813" target="http://www.rfc-editor.org/rfc/rfc5652.txt"/></reference> <reference anchor="RFC5751"><front><title>Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.2 Message Specification</title><author initials="B." surname="Ramsdell" fullname="B. Ramsdell"><organization/></author><author initials="S." surname="Turner" fullname="S. Turner"><organization/></author><date year="2010" month="January"/><abstract><t>This document defines Secure/Multipurpose Internet Mail Extensions (S/MIME) version 3.2. S/MIME provides a consistent way to send and receive secure MIME data. Digital signatures provide authentication, message integrity, and non-repudiation with proof of origin. Encryption provides data confidentiality. Compression can be used to reduce data size. This document obsoletes RFC 3851. [STANDARDS-TRACK]</t></abstract></front><seriesInfo name="RFC" value="5751"/><format type="TXT" octets="98638" target="http://www.rfc-editor.org/rfc/rfc5751.txt"/></reference> <reference anchor="RFC5752"><front><title>Multiple Signatures in Cryptographic Message Syntax (CMS)</title><author initials="S." surname="Turner" fullname="S. Turner"><organization/></author><author initials="J." surname="Schaad" fullname="J. Schaad"><organization/></author><date year="2010" month="January"/><abstract><t>Cryptographic Message Syntax (CMS) SignedData includes the SignerInfo structure to convey per-signer information. SignedData supports multiple signers and multiple signature algorithms per signer with multiple SignerInfo structures. If a signer attaches more than one SignerInfo, there are concerns that an attacker could perform a downgrade attack by removing the SignerInfo(s) with the \'strong' algorithm(s). This document defines the multiple-signatures attribute, its generation rules, and its processing rules to allow signers to convey multiple SignerInfo objects while protecting against downgrade attacks. Additionally, this attribute may assist during periods of algorithm migration. [STANDARDS-TRACK]</t></abstract></front><seriesInfo name="RFC" value="5752"/><format type="TXT" octets="34502" target="http://www.rfc-editor.org/rfc/rfc5752.txt"/></reference> <reference anchor="RFC5869"><front><title>HMAC-based Extract-and-Expand Key Derivation Function (HKDF)</title><author initials="H." surname="Krawczyk" fullname="H. Krawczyk"><organization/></author><author initials="P." surname="Eronen" fullname="P. Eronen"><organization/></author><date year="2010" month="May"/><abstract><t>This document specifies a simple Hashed Message Authentication Code (HMAC)-based key derivation function (HKDF), which can be used as a building block in various protocols and applications. The key derivation function (KDF) is intended to support a wide range of applications and requirements, and is conservative in its use of cryptographic hash functions. This document is not an Internet Standards Track specification; it is published for informational purposes.</t></abstract></front><seriesInfo name="RFC" value="5869"/><format type="TXT" octets="25854" target="http://www.rfc-editor.org/rfc/rfc5869.txt"/></reference> <reference anchor="RFC5990"><front><title>Use of the RSA-KEM Key Transport Algorithm in the Cryptographic Message Syntax (CMS)</title><author initials="J." surname="Randall" fullname="J. Randall"><organization/></author><author initials="B." surname="Kaliski" fullname="B. Kaliski"><organization/></author><author initials="J." surname="Brainard" fullname="J. Brainard"><organization/></author><author initials="S." surname="Turner" fullname="S. Turner"><organization/></author><date year="2010" month="September"/><abstract><t>The RSA-KEM Key Transport Algorithm is a one-pass (store-and-forward) mechanism for transporting keying data to a recipient using the recipient's RSA public key. ("KEM" stands for "key encapsulation mechanism".) This document specifies the conventions for using the RSA-KEM Key Transport Algorithm with the Cryptographic Message Syntax (CMS). The ASN.1 syntax is aligned with an expected forthcoming change to American National Standard (ANS) X9.44.</t></abstract></front><seriesInfo name="RFC" value="5990"/><format type="TXT" octets="52579" target="http://www.rfc-editor.org/rfc/rfc5990.txt"/></reference> <reference anchor="RFC6090"><front><title>Fundamental Elliptic Curve Cryptography Algorithms</title><author initials="D." surname="McGrew" fullname="D. McGrew"><organization/></author><author initials="K." surname="Igoe" fullname="K. Igoe"><organization/></author><author initials="M." surname="Salter" fullname="M. Salter"><organization/></author><date year="2011" month="February"/><abstract><t>This note describes the fundamental algorithms of Elliptic Curve Cryptography (ECC) as they were defined in some seminal references from 1994 and earlier. These descriptions may be useful for implementing the fundamental algorithms without using any of the specialized methods that were developed in following years. Only elliptic curves defined over fields of characteristic greater than three are in scope; these curves are those used in Suite B. This document is not an Internet Standards Track specification; it is published for informational purposes.</t></abstract></front><seriesInfo name="RFC" value="6090"/><format type="TXT" octets="75993" target="http://www.rfc-editor.org/rfc/rfc6090.txt"/></reference> <reference anchor="RFC6151"><front><title>Updated Security Considerations for the MD5 Message-Digest and the HMAC-MD5 Algorithms</title><author initials="S." surname="Turner" fullname="S. Turner"><organization/></author><author initials="L." surname="Chen" fullname="L. Chen"><organization/></author><date year="2011" month="March"/><abstract><t>This document updates the security considerations for the MD5 message digest algorithm. It also updates the security considerations for HMAC-MD5. This document is not an Internet Standards Track specification; it is published for informational purposes.</t></abstract></front><seriesInfo name="RFC" value="6151"/><format type="TXT" octets="14662" target="http://www.rfc-editor.org/rfc/rfc6151.txt"/></reference> <reference anchor="RFC6979" target="http://www.rfc-editor.org/info/rfc6979"><front><title>Deterministic Usage of the Digital Signature Algorithm (DSA) and Elliptic Curve Digital Signature Algorithm (ECDSA)</title><author initials="T." surname="Pornin" fullname="T. Pornin"><organization/></author><date year="2013" month="August"/><abstract><t>This document defines a deterministic digital signature generation procedure. Such signatures are compatible with standard Digital Signature Algorithm (DSA) and Elliptic Curve Digital Signature Algorithm (ECDSA) digital signatures and can be processed with unmodified verifiers, which need not be aware of the procedure described therein. Deterministic signatures retain the cryptographic security features associated with digital signatures but can be more easily implemented in various environments, since they do not need access to a source of high-quality randomness.</t></abstract></front><seriesInfo name="RFC" value="6979"/><seriesInfo name="DOI" value="10.17487/RFC6979"/></reference> <reference anchor="RFC7159"><front><title>The JavaScript Object Notation (JSON) Data Interchange Format</title><author initials="T." surname="Bray" fullname="T. Bray"><organization/></author><date year="2014" month="March"/><abstract><t>JavaScript Object Notation (JSON) is a lightweight, text-based, language-independent data interchange format. It was derived from the ECMAScript Programming Language Standard. JSON defines a small set of formatting rules for the portable representation of structured data.</t><t> This document removes inconsistencies with other specifications of JSON, repairs specification errors, and offers experience-based interoperability guidance.</t></abstract></front><seriesInfo name="RFC" value="7159"/><format type="TXT" octets="27451" target="http://www.rfc-editor.org/rfc/rfc7159.txt"/></reference> <reference anchor="RFC7252" target="http://www.rfc-editor.org/info/rfc7252"><front><title>The Constrained Application Protocol (CoAP)</title><author initials="Z." surname="Shelby" fullname="Z. Shelby"><organization/></author><author initials="K." surname="Hartke" fullname="K. Hartke"><organization/></author><author initials="C." surname="Bormann" fullname="C. Bormann"><organization/></author><date year="2014" month="June"/><abstract><t>The Constrained Application Protocol (CoAP) is a specialized web transfer protocol for use with constrained nodes and constrained (e.g., low-power, lossy) networks. The nodes often have 8-bit microcontrollers with small amounts of ROM and RAM, while constrained networks such as IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs) often have high packet error rates and a typical throughput of 10s of kbit/s. The protocol is designed for machine- to-machine (M2M) applications such as smart energy and building automation.</t><t>CoAP provides a request/response interaction model between application endpoints, supports built-in discovery of services and resources, and includes key concepts of the Web such as URIs and Internet media types. CoAP is designed to easily interface with HTTP for integration with the Web while meeting specialized requirements such as multicast support, very low overhead, and simplicity for constrained environments.</t></abstract></front><seriesInfo name="RFC" value="7252"/><seriesInfo name="DOI" value="10.17487/RFC7252"/></reference> <reference anchor="RFC7515"><front><title>JSON Web Signature (JWS)</title><author initials="M." surname="Jones" fullname="M. Jones"><organization/></author><author initials="J." surname="Bradley" fullname="J. Bradley"><organization/></author><author initials="N." surname="Sakimura" fullname="N. Sakimura"><organization/></author><date year="2015" month="May"/><abstract><t>JSON Web Signature (JWS) represents content secured with digital signatures or Message Authentication Codes (MACs) using JSON-based data structures. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) specification and an IANA registry defined by that specification. Related encryption capabilities are described in the separate JSON Web Encryption (JWE) specification.</t></abstract></front><seriesInfo name="RFC" value="7515"/><format type="TXT" octets="131110" target="http://www.rfc-editor.org/rfc/rfc7515.txt"/></reference> <reference anchor="RFC7516"><front><title>JSON Web Encryption (JWE)</title><author initials="M." surname="Jones" fullname="M. Jones"><organization/></author><author initials="J." surname="Hildebrand" fullname="J. Hildebrand"><organization/></author><date year="2015" month="May"/><abstract><t>JSON Web Encryption (JWE) represents encrypted content using JSON-based data structures. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) specification and IANA registries defined by that specification. Related digital signature and Message Authentication Code (MAC) capabilities are described in the separate JSON Web Signature (JWS) specification.</t></abstract></front><seriesInfo name="RFC" value="7516"/><format type="TXT" octets="108322" target="http://www.rfc-editor.org/rfc/rfc7516.txt"/></reference> <reference anchor="RFC7517"><front><title>JSON Web Key (JWK)</title><author initials="M." surname="Jones" fullname="M. Jones"><organization/></author><date year="2015" month="May"/><abstract><t>A JSON Web Key (JWK) is a JavaScript Object Notation (JSON) data structure that represents a cryptographic key. This specification also defines a JWK Set JSON data structure that represents a set of JWKs. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) specification and IANA registries established by that specification.</t></abstract></front><seriesInfo name="RFC" value="7517"/><format type="TXT" octets="93906" target="http://www.rfc-editor.org/rfc/rfc7517.txt"/></reference> <reference anchor="RFC7518"><front><title>JSON Web Algorithms (JWA)</title><author initials="M." surname="Jones" fullname="M. Jones"><organization/></author><date year="2015" month="May"/><abstract><t>This specification registers cryptographic algorithms and identifiers to be used with the JSON Web Signature (JWS), JSON Web Encryption (JWE), and JSON Web Key (JWK) specifications. It defines several IANA registries for these identifiers.</t></abstract></front><seriesInfo name="RFC" value="7518"/><format type="TXT" octets="155905" target="http://www.rfc-editor.org/rfc/rfc7518.txt"/></reference> <reference anchor="RFC7539" target="http://www.rfc-editor.org/info/rfc7539"><front><title>ChaCha20 and Poly1305 for IETF Protocols</title><author initials="Y." surname="Nir" fullname="Y. Nir"><organization/></author><author initials="A." surname="Langley" fullname="A. Langley"><organization/></author><date year="2015" month="May"/><abstract><t>This document defines the ChaCha20 stream cipher as well as the use of the Poly1305 authenticator, both as stand-alone algorithms and as a "combined mode", or Authenticated Encryption with Associated Data (AEAD) algorithm.</t><t>This document does not introduce any new crypto, but is meant to serve as a stable reference and an implementation guide. It is a product of the Crypto Forum Research Group (CFRG).</t></abstract></front><seriesInfo name="RFC" value="7539"/><seriesInfo name="DOI" value="10.17487/RFC7539"/></reference> <reference anchor="I-D.irtf-cfrg-curves"><front><title>Elliptic Curves for Security</title><author initials="A" surname="Langley" fullname="Adam Langley"><organization/></author><author initials="R" surname="Salz" fullname="Rich Salz"><organization/></author><date month="March" day="24" year="2015"/><abstract><t>This memo describes an algorithm for deterministically generating parameters for elliptic curves over prime fields offering high practical security in cryptographic applications, including Transport Layer Security (TLS) and X.509 certificates. It also specifies a specific curve at the ~128-bit security level and a specific curve at the ~224-bit security level.</t></abstract></front><seriesInfo name="Internet-Draft" value="draft-irtf-cfrg-curves-02"/><format type="TXT" target="http://www.ietf.org/internet-drafts/draft-irtf-cfrg-curves-02.txt"/></reference> <reference anchor="I-D.irtf-cfrg-eddsa"><front><title>Edwards-curve Digital Signature Algorithm (EdDSA)</title><author initials="S" surname="Josefsson" fullname="Simon Josefsson"><organization/></author><author initials="I" surname="Liusvaara" fullname="Ilari Liusvaara"><organization/></author><date month="October" day="8" year="2015"/><abstract><t>The elliptic curve signature scheme Edwards-curve Digital Signature Algorithm (EdDSA) is described. The algorithm is instantiated with recommended parameters for the Curve25519 and Curve448 curves. An example implementation and test vectors are provided. NOTE: Anything not about Ed25519 in this document is extremely premature and there is at least one FIXME that makes some things unimplementable.</t></abstract></front><seriesInfo name="Internet-Draft" value="draft-irtf-cfrg-eddsa-00"/><format type="TXT" target="http://www.ietf.org/internet-drafts/draft-irtf-cfrg-eddsa-00.txt"/></reference> <reference anchor="I-D.ietf-cose-msg"><front><title>CBOR Encoded Message Syntax</title><author initials="J" surname="Schaad" fullname="Jim Schaad"><organization/></author><author initials="B" surname="Campbell" fullname="Brian Campbell"><organization/></author><date month="September" day="21" year="2015"/><abstract><t>Concise Binary Object Representation (CBOR) is data format designed for small code size and small message size. There is a need for the ability to have the basic security services defined for this data format. This document specifies how to do signatures, message authentication codes and encryption using this data format.</t></abstract></front><seriesInfo name="Internet-Draft" value="draft-ietf-cose-msg-05"/><format type="TXT" target="http://www.ietf.org/internet-drafts/draft-ietf-cose-msg-05.txt"/></reference> <reference anchor="AES-GCM"><front><title>NIST Special Publication 800-38D: Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC.</title><author initials="M." surname="Dworkin"><organization>U.S. National Institute of Standards and Technology</organization></author><date year="2007" month="Nov"/></front><format target="https://csrc.nist.gov/publications/nistpubs/800-38D/SP-800-38D.pdf" type="PDF"/></reference><reference anchor="MAC"><front><title>FIPS PUB 113: Computer Data Authentication</title><author initials="N" surname="NiST"/><date year="1985" month="May"/></front><format target="http://csrc.nist.gov/publications/fips/fips113/fips113.html" type="HTML"/></reference><reference anchor="DSS"><front><title>Digital Signature Standard (DSS)</title><author><organization>U.S. National Institute of Standards and Technology</organization></author><date year="2013" month="July"/></front><format target="http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.186-4.pdf" type="PDF"/></reference><reference anchor="SP800-56A"><front><title>NIST Special Publication 800-56A: Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography</title><author initials="E." surname="Barker"><organization>U.S. National Institute of Standards and Technology</organization></author><author initials="L." surname="Chen"><organization>U.S. National Institute of Standards and Technology</organization></author><author initials="A." surname="Roginsky"><organization>U.S. National Institute of Standards and Technology</organization></author><author initials="M." surname="Smid"><organization>Orion Security Solutions, Inc.</organization></author><date year="2013" month="May"/></front><format target="https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-56Ar2.pdf" type="PDF"/></reference><reference anchor="SEC1"><front><title>SEC 1: Elliptic Curve Cryptography</title><author><organization>Standards for Efficient Cryptography Group</organization></author><date year="2009" month="May"/></front><format target="http://www.secg.org/sec1-v2.pdf" type="PDF"/></reference><reference anchor="MultiPrimeRSA"><front><title>On the Security of Multi-prime RSA</title><author initials="M. J." surname="Hinek"><organization>University of Waterloo</organization></author><author initials="D. R." surname="Cheriton"><organization>University of Waterloo</organization></author><date year="2006" month="June"/></front><format target="http://cacr.uwaterloo.ca/techreports/2006/cacr2006-16.pdf" type="PDF"/></reference><reference anchor="PVSig"><front><title>Formal Security Proofs for a Signature Scheme with Partial Message Recover</title><author initials="D." surname="Brown"/><author initials="D." surname="Johnson"/><date year="2000" month="February"/></front><format target="https://www.certicom.com/images/pdfs/CerticomWP-PVSigSec_login.pdf" type="PDF"/></reference></references>
<section anchor="Grammar_Appendix" title="CDDL Grammar" toc="default">
<t>For people who prefer using a formal language to describe the syntax of the CBOR, in this section a CDDL grammar is given that corresponds to <xref target="I-D.greevenbosch-appsawg-cbor-cddl" pageno="false" format="default"/>. This grammar is informational, in the event of differences between this grammar and the prose, the prose is considered to be authorative. </t>
<t>The collected CDDL can be extracted from the XML version of this document via the following XPath expression below. (Depending on the XPath evaluator one is using, it may be necessary to deal with > as an entity.) </t>
<t><figure title="" suppress-title="false" align="left" alt="" width="" height=""><artwork type="XPATH" xml:space="preserve" name="" align="left" alt="" width="" height="">
//artwork[@type='CDDL']/text()
</artwork></figure> </t>
</section>
<section anchor="examples" title="Examples" toc="default">
<t>The examples can be found at https://github.com/cose-wg/Examples. The file names in each section correspond the the same file names in the repository. I am currently still in the process of getting the examples up there along with some control information for people to be able to check and reproduce the examples. </t>
<t>Examples may have some features that are in questions but not yet incorporated in the document. </t>
<t>To make it easier to read, the examples are presented using the CBOR's diagnostic notation rather than a binary dump. A ruby based tool exists to convert between a number of formats. This tool can be installed with the command line: </t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
gem install cbor-diag
</artwork>
</figure>
<t>The diagnostic notation can be converted into binary files using the following command line: </t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height="">
diag2cbor < inputfile > outputfile
</artwork>
</figure>
<t>The examples can be extracted from the XML version of this docuent via an XPath expression as all of the artwork is tagged with the attribute type='CBORdiag'. </t>
<section title="Examples of MAC messages" toc="default">
<section anchor="Mac-04" title="Shared Secret Direct MAC" toc="default"><t>This example users the following: <list style="symbols"><t>MAC: AES-CMAC, 256-bit key, trucated to 64 bits</t><t>Recipient class: direct shared secret</t><t>File name: Mac-04</t></list> </t><t>Size of binary file is 73 bytes </t><figure title="" suppress-title="false" align="left" alt="" width="" height=""><artwork type="CBORdiag" xml:space="preserve" name="" align="left" alt="" width="" height="">
996( [
h'a1016f4145532d434d41432d3235362f3634',
{
},
h'546869732069732074686520636f6e74656e742e',
h'd9afa663dd740848',
[
[
h'',
{
1: -6,
4: h'6f75722d736563726574'
},
h''
]
]
])</artwork></figure> </section>
<section anchor="Mac-01" title="ECDH Direct MAC" toc="default"><t>This example uses the following: <list style="symbols"><t>MAC: HMAC w/SHA-256, 256-bit key </t><t>Recipient class: ECDH key agreement, two static keys, HKDF w/ context structure</t></list> </t><t>Size of binary file is 217 bytes </t><figure title="" suppress-title="false" align="left" alt="" width="" height=""><artwork type="CBORdiag" xml:space="preserve" name="" align="left" alt="" width="" height="">
996( [
h'a10104',
{
},
h'546869732069732074686520636f6e74656e742e',
h'2ba937ca03d76c3dbad30cfcbaeef586f9c0f9ba616ad67e9205d38576ad9
930',
[
[
h'',
{
1: 52,
4: h'6d65726961646f632e6272616e64796275636b406275636b6c61
6e642e6578616d706c65',
-3: h'706572656772696e2e746f6f6b407475636b626f726f7567682
e6578616d706c65',
"apu": h'4d8553e7e74f3c6a3a9dd3ef286a8195cbf8a23d19558ccf
ec7d34b824f42d92bd06bd2c7f0271f0214e141fb779ae2856abf585a58368b01
7e7f2a9e5ce4db5'
},
h''
]
]
])</artwork></figure> </section>
<section anchor="Mac-02" title="Wrapped MAC" toc="default"><t>This example uses the following: <list style="symbols"><t>MAC: AES-MAC, 128-bit key, truncated to 64 bits</t><t>Recipient class: AES keywrap w/ a pre-shared 256-bit key</t></list> </t><t>Size of binary file is 124 bytes </t><figure title="" suppress-title="false" align="left" alt="" width="" height=""><artwork type="CBORdiag" xml:space="preserve" name="" align="left" alt="" width="" height="">
996( [
h'a1016e4145532d3132382d4d41432d3634',
{
},
h'546869732069732074686520636f6e74656e742e',
h'6d1fa77b2dd9146a',
[
[
h'',
{
1: -5,
4: h'30313863306165352d346439622d343731622d626664362d6565
66333134626337303337'
},
h'711ab0dc2fc4585dce27effa6781c8093eba906f227b6eb0'
]
]
])</artwork></figure> </section>
<section anchor="Mac-03" title="Multi-recipient MAC message" toc="default"><t>This example uses the following: <list style="symbols"><t>MAC: HMAC w/ SHA-256, 128-bit key</t><t>Recipient class: Uses three different methods <list style="numbers"><t>ECDH Ephemeral-Static, Curve P-521, AES-Key Wrap w/ 128-bit key</t><t>RSA-OAEP w/ SHA-256</t><t>AES-Key Wrap w/ 256-bit key</t></list> </t></list> </t><t>Size of binary file is 672 bytes </t><figure title="" suppress-title="false" align="left" alt="" width="" height=""><artwork type="CBORdiag" xml:space="preserve" name="" align="left" alt="" width="" height="">
996( [
h'a10104',
{
},
h'546869732069732074686520636f6e74656e742e',
h'7aaa6e74546873061f0a7de21ff0c0658d401a68da738dd893748651983ce
1d0',
[
[
h'',
{
1: 55,
4: h'62696c626f2e62616767696e7340686f626269746f6e2e657861
6d706c65',
-1: {
1: 2,
-1: 3,
-2: h'43b12669acac3fd27898ffba0bcd2e6c366d53bc4db71f909
a759304acfb5e18cdc7ba0b13ff8c7636271a6924b1ac63c02688075b55ef2d61
3574e7dc242f79c3',
-3: h'812dd694f4ef32b11014d74010a954689c6b6e8785b333d1a
b44f22b9d1091ae8fc8ae40b687e5cfbe7ee6f8b47918a07bb04e9f5b1a51a334
a16bc09777434113'
}
},
h'f20ad9c96134f3c6be4f75e7101c0ecc5efa071ff20a87fd1ac285109
41ee0376573e2b384b56b99'
],
[
h'',
{
1: -26,
4: h'62696c626f2e62616767696e7340686f626269746f6e2e657861
6d706c65'
},
h'46c4f88069b650909a891e84013614cd58a3668f88fa18f3852940a20
b35098591d3aacf91c125a2595cda7bee75a490579f0e2f20fd6bc956623bfde3
029c318f82c426dac3463b261c981ab18b72fe9409412e5c7f2d8f2b5abaf780d
f6a282db033b3a863fa957408b81741878f466dcc437006ca21407181a016ca60
8ca8208bd3c5a1ddc828531e30b89a67ec6bb97b0c3c3c92036c0cb84aa0f0ce8
c3e4a215d173bfa668f116ca9f1177505afb7629a9b0b5e096e81d37900e06f56
1a32b6bc993fc6d0cb5d4bb81b74e6ffb0958dac7227c2eb8856303d989f93b4a
051830706a4c44e8314ec846022eab727e16ada628f12ee7978855550249ccb58
'
],
[
h'',
{
1: -5,
4: h'30313863306165352d346439622d343731622d626664362d6565
66333134626337303337'
},
h'0b2c7cfce04e98276342d6476a7723c090dfdd15f9a518e7736549e99
8370695e6d6a83b4ae507bb'
]
]
])</artwork></figure> </section>
</section>
<section title="Examples of Encrypted Messages" toc="default">
<section anchor="Enc-01" title="Direct ECDH" toc="default"><t>This example uses the following: <list style="symbols"><t>CEK: AES-GCM w/ 128-bit key</t><t>Recipient class: ECDH Ephemeral-Static, Curve P-256</t></list> </t><t>Size of binary file is 184 bytes </t><figure title="" suppress-title="false" align="left" alt="" width="" height=""><artwork type="CBORdiag" xml:space="preserve" name="" align="left" alt="" width="" height="">
998( [
h'a10101',
{
5: h'c9cf4df2fe6c632bf7886413'
},
h'45fce2814311024d3a479e7d3eed063850f3f0b9f3f948677e3ae9869bcf9
ff4e1763812',
[
[
h'',
{
1: 50,
4: h'6d65726961646f632e6272616e64796275636b406275636b6c61
6e642e6578616d706c65',
-1: {
1: 2,
-1: 1,
-2: h'98f50a4ff6c05861c8860d13a638ea56c3f5ad7590bbfbf05
4e1c7b4d91d6280',
-3: h'f01400b089867804b8e9fc96c3932161f1934f4223069170d
924b7e03bf822bb'
}
},
h''
]
]
])</artwork></figure> </section>
<section anchor="Enc-02" title="Direct plus Key Derivation" toc="default"><t>This example uses the following: <list style="symbols"><t>CEK: AES-CCM w/128-bit key, trucate the tag to 64-bits</t><t>Recipient class: Use HKDF on a shared secret with the following implicit fields as part of the context. <list style="symbols"><t>APU identity: "lighting-client"</t><t>APV identity: "lighting-server"</t><t>Supplimentary Public Other: "Encryption Example 02"</t></list> </t></list> </t><t>Size of binary file is 97 bytes </t><figure title="" suppress-title="false" align="left" alt="" width="" height=""><artwork type="CBORdiag" xml:space="preserve" name="" align="left" alt="" width="" height="">
998( [
h'a1010a',
{
5: h'89f52f65a1c580933b5261a7'
},
h'7b9dcfa42c4e1d3182c402dc18ef8b5637de4fb62cf1dd156ea6e6e0',
[
[
h'',
{
1: "dir+kdf",
4: h'6f75722d736563726574',
-20: h'61616262636364646565666667676868'
},
h''
]
]
])</artwork></figure> </section>
</section>
<section title="Examples of Signed Message" toc="default">
<section anchor="Sig-01" title="Single Signature" toc="default"><t>This example uses the following: <list style="symbols"><t>Signature Algorithm: RSA-PSS w/ SHA-384, MGF-1</t></list> </t><t>Size of binary file is 332 bytes </t><figure title="" suppress-title="false" align="left" alt="" width="" height=""><artwork type="CBORdiag" xml:space="preserve" name="" align="left" alt="" width="" height="">
999( [
h'',
{
},
h'546869732069732074686520636f6e74656e742e',
[
[
h'a20165505333383404581e62696c626f2e62616767696e7340686f626
269746f6e2e6578616d706c65',
{
},
h'6d9d88a90ef4d6d7c0079fb11a33c855e2274c773f358df43b68f7873
eeda210692a61d70cd6a24ba0e3d82e359384be09faafea496bb0ed16f02091c4
8c02f33574edab5b3e334bae68d19580021327cc131fbee38eb0b28289dbce118
3f9067891b17fe752674b80437da02e9928ab7a155fef707b11d2bd38a71f224f
53170480116d96cc3f7266487b268679a13cdedffa93252a550371acc19971369
b58039056b308cc4e158bebe7c55db7874442d4321fd27f17dbb820ef19f43dcc
16cd50ccdd1b7dfd7cdde239a9245af41d949cdbbf1337ca254af20eeb167a62d
a5a51c83899c6f6e7c7e01dc3db21a250092a69fc635b74a2e54f5c98cb955d83
'
]
]
])</artwork></figure> </section>
<section anchor="Sig-02" title="Multiple Signers" toc="default"><t>This example uses the following: <list style="symbols"><t>Signature Algorithm: RSA-PSS w/ SHA-256, MGF-1</t><t>Signature Algorithm: ECDSA w/ SHA-512, Curve P-521</t></list> </t><t>Size of binary file is 498 bytes </t><figure title="" suppress-title="false" align="left" alt="" width="" height=""><artwork type="CBORdiag" xml:space="preserve" name="" align="left" alt="" width="" height="">
999( [
h'',
{
},
h'546869732069732074686520636f6e74656e742e',
[
[
h'a1013819',
{
4: h'62696c626f2e62616767696e7340686f626269746f6e2e657861
6d706c65'
},
h'0ee972d931c7ab906e4bb71b80da0cc99c104fa53ebbf1f2cf7b668b9
3d766d3d2da28299f074675bb0db3cd0792ba83050c23c96795d58f9c7d68f66a
bbb8f35af8a0b5df369517b6db85e2cb62d852b666bc135c9022e46b538f78c26
adc2668963e74a019de718254385bb9cb137926ad6a88d1ff70043f85e555fb57
84107ce6e9de7c89c4fbadf8eca363a35f415f7a23523a8331b1aa2dfbac59a06
3e4357bde8e53fe34195d59bcda37d2c604804fffe60362e81476436aaa677129
f34b26639fc41b8e758e5edf273079c61b30130f0f83c57aa6856347e2556f718
eaf79a1fee1397a4f0b16b1b34db946eaaff10c793e5d1e681cb21c4fd20c5fdf
'
],
[
h'',
{
1: -9,
4: h'62696c626f2e62616767696e7340686f626269746f6e2e657861
6d706c65'
},
h'0118eaa7d62778b5a9525a583f06b115d80cd246bc930f0c2850588ee
c85186b427026e096a076bfab738215f354be59f57643a7f6b2c92535cf3c37ee
2746a908ab1dcc673a63f327d9eff852b874f7a98b6638c7054fdeeaa3dce6542
4a21bd5dc728acedda7fcae6df6fc3298ff51ac911603a0f26d066935dccb85ea
eb0ae6d0e6'
]
]
])</artwork></figure> </section>
</section>
<section title="COSE Keys" toc="default">
<section title="Public Keys" toc="default"><t>This is an example of a COSE Key set. This example includes the public keys for all of the previous examples. </t><t>In order the keys are: <list style="symbols"><t>An EC key with a kid of "meriadoc.brandybuck@buckland.example"</t><t>An EC key with a kid of "peregrin.took@tuckborough.example"</t><t>An EC key with a kid of "bilbo.baggins@hobbiton.example"</t><t>An RSA key with a kid of "bilbo.baggins@hobbiton.example"</t></list> </t><t>Size of binary file is 703 bytes </t><figure title="" suppress-title="false" align="left" alt="" width="" height=""><artwork type="CBORdiag" xml:space="preserve" name="" align="left" alt="" width="" height="">
[
{
-1: 1,
-2: h'65eda5a12577c2bae829437fe338701a10aaa375e1bb5b5de108de4
39c08551d',
-3: h'1e52ed75701163f7f9e40ddf9f341b3dc9ba860af7e0ca7ca7e9eec
d0084d19c',
1: 2,
2: h'6d65726961646f632e6272616e64796275636b406275636b6c616e64
2e6578616d706c65'
},
{
-1: 3,
-2: h'0072992cb3ac08ecf3e5c63dedec0d51a8c1f79ef2f82f94f3c737b
f5de7986671eac625fe8257bbd0394644caaa3aaf8f27a4585fbbcad0f2457620
085e5c8f42ad',
-3: h'01dca6947bce88bc5790485ac97427342bc35f887d86d65a089377e
247e60baa55e4e8501e2ada5724ac51d6909008033ebc10ac999b9d7f5cc2519f
3fe1ea1d9475',
1: 2,
2: h'62696c626f2e62616767696e7340686f626269746f6e2e6578616d70
6c65'
},
{
-1: 1,
-2: h'98f50a4ff6c05861c8860d13a638ea56c3f5ad7590bbfbf054e1c7b
4d91d6280',
-3: h'f01400b089867804b8e9fc96c3932161f1934f4223069170d924b7e
03bf822bb',
1: 2,
2: h'706572656772696e2e746f6f6b407475636b626f726f7567682e6578
616d706c65'
},
{
-2: h'9f810fb4038273d02591e4073f31d2b6001b82cedb4d92f050165d4
7cfcab8a3c41cb778ac7553793f8ef975768d1a2374d8712564c3bcd77b9ea434
544899407cff0099920a931a24c4414852ab29bdb0a95c0653f36c60e60bf90b6
258dda56f37047ba5c2d1d029af9c9d40bac7aa41c78a0dd1068add699e808fea
011ea1441d8a4f7bb4e97be39f55f1ddd44e9c4ba335159703d4d34b603e65147
a4f23d6d3c0996c75edee846a82d190ae10783c961cf0387aed2106d2d0555b6f
d937fad5535387e0ff72ffbe78941402b0b822ea2a74b6058c1dabf9b34a76cb6
3b87faa2c6847b8e2837fff91186e6b1c14911cf989a89092a81ce601ddacd3f9
cf',
-1: h'010001',
1: 3,
2: h'62696c626f2e62616767696e7340686f626269746f6e2e6578616d70
6c65'
}
]</artwork></figure> </section>
<section title="Private Keys" toc="default"><t>This is an example of a COSE Key set. This example includes the private keys for all of the previous examples. </t><t>In order the keys are: <list style="symbols"><t>An EC key with a kid of "meriadoc.brandybuck@buckland.example"</t><t>A shared-secret key with a kid of "our-secret"</t><t>An EC key with a kid of "peregrin.took@tuckborough.example"</t><t>A shared-secret key with a kid of "018c0ae5-4d9b-471b-bfd6-eef314bc7037"</t><t>An EC key with a kid of "bilbo.baggins@hobbiton.example"</t><t>An RSA key with a kid of "bilbo.baggins@hobbiton.example"</t></list> </t><t>Size of binary file is 1884 bytes </t><figure title="" suppress-title="false" align="left" alt="" width="" height=""><artwork type="CBORdiag" xml:space="preserve" name="" align="left" alt="" width="" height="">
[
{
1: 2,
2: h'6d65726961646f632e6272616e64796275636b406275636b6c616e64
2e6578616d706c65',
-1: 1,
-2: h'65eda5a12577c2bae829437fe338701a10aaa375e1bb5b5de108de4
39c08551d',
-3: h'1e52ed75701163f7f9e40ddf9f341b3dc9ba860af7e0ca7ca7e9eec
d0084d19c',
-4: h'aff907c99f9ad3aae6c4cdf21122bce2bd68b5283e6907154ad9118
40fa208cf'
},
{
1: 4,
2: h'6f75722d736563726574',
-1: h'849b57219dae48de646d07dbb533566e976686457c1491be3a76dce
a6c427188'
},
{
1: 2,
2: h'62696c626f2e62616767696e7340686f626269746f6e2e6578616d70
6c65',
-1: 3,
-2: h'0072992cb3ac08ecf3e5c63dedec0d51a8c1f79ef2f82f94f3c737b
f5de7986671eac625fe8257bbd0394644caaa3aaf8f27a4585fbbcad0f2457620
085e5c8f42ad',
-3: h'01dca6947bce88bc5790485ac97427342bc35f887d86d65a089377e
247e60baa55e4e8501e2ada5724ac51d6909008033ebc10ac999b9d7f5cc2519f
3fe1ea1d9475',
-4: h'00085138ddabf5ca975f5860f91a08e91d6d5f9a76ad4018766a476
680b55cd339e8ab6c72b5facdb2a2a50ac25bd086647dd3e2e6e99e84ca2c3609
fdf177feb26d'
},
{
1: 2,
-1: 1,
2: h'706572656772696e2e746f6f6b407475636b626f726f7567682e6578
616d706c65',
-2: h'98f50a4ff6c05861c8860d13a638ea56c3f5ad7590bbfbf054e1c7b
4d91d6280',
-3: h'f01400b089867804b8e9fc96c3932161f1934f4223069170d924b7e
03bf822bb',
-4: h'02d1f7e6f26c43d4868d87ceb2353161740aacf1f7163647984b522
a848df1c3'
},
{
1: 4,
2: h'30313863306165352d346439622d343731622d626664362d65656633
3134626337303337',
-1: h'849b57219dae48de646d07dbb533566e976686457c1491be3a76dce
a6c427188'
},
{
1: 3,
2: h'62696c626f2e62616767696e7340686f626269746f6e2e6578616d70
6c65',
-2: h'9f810fb4038273d02591e4073f31d2b6001b82cedb4d92f050165d4
7cfcab8a3c41cb778ac7553793f8ef975768d1a2374d8712564c3bcd77b9ea434
544899407cff0099920a931a24c4414852ab29bdb0a95c0653f36c60e60bf90b6
258dda56f37047ba5c2d1d029af9c9d40bac7aa41c78a0dd1068add699e808fea
011ea1441d8a4f7bb4e97be39f55f1ddd44e9c4ba335159703d4d34b603e65147
a4f23d6d3c0996c75edee846a82d190ae10783c961cf0387aed2106d2d0555b6f
d937fad5535387e0ff72ffbe78941402b0b822ea2a74b6058c1dabf9b34a76cb6
3b87faa2c6847b8e2837fff91186e6b1c14911cf989a89092a81ce601ddacd3f9
cf',
-1: h'010001',
-3: h'6d6502f41f84151228f24a467e1d19bb218fbcc34abd858db41fe29
221fd936d1e4fe3b5abf23bf1e8999295f15d0d144c4b362ec3514bef2e25bbd0
f80d62ae4c0c48c90ad49dd74c681dae10a4bbd81195d63bb0d03f00a64687e43
aeb5ff8dab20d2d109ef16fa7677e2e8bfa8e7e42e72bd4160c3aa9688b00f9b3
3059648316ed8c5016309074cc1332d81aa39ed389e8a9eab5844c414c704e05d
90c5e2b85854ab5054ea5f83a84896c6a83cdac5edda1f8b3274f7d38e8039826
8462a33ef9b525107c60ac8564c19cfe6e0e3775f242a1cafd3b9617d225dacf7
4ce4f972976d61b057f82ff9870aea056aeee076c3df1cfc718d539c3a906b433
c1',
-4: h'dd297183f0f04d725c6fad3de51a17ca0402019e519c0bd9967a35c
a11ed9d47b1fdfa7b019ffd9d168eec75fff9215f1907aeb5aa364c38c3016538
56ea64f2bc3d251d00cd9d0dd9fbee2009abfd60ac986a5e36a4277afd53ec8c8
4b2787c50cb7e9f909a7e1922933844b2b9a7747e8bc4eaef44996c3e9e99bfc6
d4ab49',
-5: h'b8a136761f9c4dfe84445e24e1efe3cbbf067cf61421a532a12489b
81ce9dc2b9b937382aacea0ad3f1b47f72ed039b5319c169ad76a0f223de47ad4
7aadcc3f5e6f30c38df251d3799bb69662afc2a5bb6a757953384cd6267bcf8c8
c92e530156a01bf263cf7c117bd10fe85da91c47952a80675f76cc1de9545274b
3ba457',
-6: h'07c3d5bd792f26b8f62fe19843bbf7cbdafa2b0e60f526a15c1c2c5
94ce9d7d4d596023e615f39ab53486f5af142d0fe22c5d7477f936a77afb913d1
b7938139d88c190a7ca5bb76ea096361f294fc4f719fe4542c7cf4f9e77d13d81
72ca0f85469e0a73f8f7d0feadbda64e71587a09a74d3d41fd47bc2862c515f9f
5e8629',
-7: h'08b0e60c676e87295cf68eebf38ac45159fba7343a3c5f3763e8816
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03da5f63e7bcffb3c84903111b9ffabcb873f675d42abd02a0b6c9e2fa91d293d
5c605f',
-8: h'dcf8aabd740dd33c0c784fac06f6608b6f3d5cff57090177556a8fc
cc2a7220429eff4ee828ebe35904a090b0c7f71da1060634d526cfe370af3e4d1
5ef68a7beed931a423f157c175892cb1bbb434a0c386327e1ad8ac79a0d55aded
d707d1c7f0c601541e9421ec5a02ae3149ea1e99129305eb19ae8ece2a3293f3f
1a688e'
}
]</artwork></figure> </section>
</section>
</section>
<!--PBSE2 went away <section anchor="Header-Algorithm-Table" title="COSE Header Algorithm Label Table"> <t> This section disappears when we make a decision on password based key management.</t> <texttable> <ttcol align='left'>name</ttcol> <ttcol align='left'>algorithm</ttcol> <ttcol align='left'>label</ttcol> <ttcol align='left'>CBOR type</ttcol> <ttcol align='left'>description</ttcol> <c>p2c</c> <c>PBE</c> <c>-1</c> <c>int</c> <c></c> <c>p2s</c> <c>PBE</c> <c>-2</c> <c>bstr</c> <c></c> </texttable> </section> -->
<section title="Document Updates" toc="default">
<section title="Version -00" toc="default">
<t><list style="symbols"><t>TBD</t></list> </t>
</section>
</section>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-23 07:25:12 |