One document matched: draft-ietf-msec-mikey-dhhmac-09.txt
Differences from draft-ietf-msec-mikey-dhhmac-08.txt
Internet Engineering Task Force - MSEC WG
Internet Draft M. Euchner
Intended Category: Proposed Standard
Expires: July 2005 February 2005
HMAC-authenticated Diffie-Hellman for MIKEY
<draft-ietf-msec-mikey-dhhmac-09.txt>
IPR Statement
By submitting this Internet-Draft, I certify that any applicable patent
or other IPR claims of which I am aware have been disclosed, or will be
disclosed, and any of which I become aware will be disclosed, in accordance
with RFC 3668.
Status of this Memo
Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other groups
may also distribute working documents as Internet- Drafts.
Internet-Drafts are draft documents valid for a maximum of six months and
may be updated, replaced, or obsoleted by other documents at any time.
It is inappropriate to use Internet-Drafts as reference material or to
cite them other than a "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
Comments should be sent to the MSEC WG mailing list at
msec@securemulticast.org and to the author.
Euchner Expires - July 2005 [Page 1]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
Abstract
This document describes a light-weight point-to-point key management
protocol variant for the multimedia Internet keying (MIKEY) protocol
MIKEY, as defined in RFC 3830. In particular, this variant deploys the
classic Diffie-Hellman key agreement protocol for key establishment
featuring perfect forward secrecy in conjunction with a keyed hash message
authentication code for achieving mutual authentication and message
integrity of the key management messages exchanged. This protocol
addresses the security and performance constraints of multimedia key
management in MIKEY.
Conventions used in this document
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 [2].
Table of Contents
1. Introduction..................................................3
1.1. Definitions.................................................6
1.2. Abbreviations...............................................7
2. Scenario......................................................8
2.1. Applicability...............................................8
2.2. Relation to GKMARCH........................................10
3. DHHMAC Security Protocol.....................................11
3.1. TGK re-keying..............................................13
4. DHHMAC payload formats.......................................14
4.1. Common header payload (HDR)................................14
4.2. Key data transport payload (KEMAC).........................15
4.3. ID payload (ID)............................................16
4.4. General Extension Payload..................................16
5. Security Considerations......................................16
5.1. Security environment.......................................17
5.2. Threat model...............................................17
5.3. Security features and properties...........................20
5.4. Assumptions................................................24
Euchner Expires - July 2005 [Page 2]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
5.5. Residual risk..............................................25
5.6. Authorization and Trust Model..............................26
6. Acknowledgments............................................26
Conclusions.....................................................26
7. IANA considerations..........................................27
8. References...................................................27
8.1 Normative References.......................................27
8.2 Informative References.....................................28
Full Copyright Statement........................................30
Expiration Date.................................................31
Revision History................................................32
Author's Addresses..............................................34
1. Introduction
There is work done in IETF to develop key management schemes. For example,
IKE [14] is a widely accepted unicast scheme for IPsec, and the MSEC WG
is developing other schemes, addressed to group communication [24], [25].
For reasons discussed below, there is however a need for a scheme with
low latency, suitable for demanding cases such as real-time data over
heterogeneous networks, and small interactive groups.
As pointed out in MIKEY (see [3]), secure real-time multimedia
applications demand a particular adequate light-weight key management
scheme that cares for how to securely and efficiently establish dynamic
session keys in a conversational multimedia scenario.
In general, MIKEY scenarios cover peer-to-peer, simple-one-to-many and
small-sized groups. MIKEY in particular, describes three key management
schemes for the peer-to-peer case that all finish their task within one
round trip:
- a symmetric key distribution protocol (MIKEY-PS) based upon
pre-shared master keys;
- a public-key encryption-based key distribution protocol
(MIKEY-PK) assuming a public-key infrastructure with RSA-based
(Rivest, Shamir and Adleman) private/public keys and digital
certificates;
- and a Diffie-Hellman key agreement protocol (MIKEY-DHSIGN)
Euchner Expires - July 2005 [Page 3]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
deploying digital signatures and certificates.
All these three key management protocols are designed such that they
complete their work within just one round trip. This requires depending
on loosely synchronized clocks and deploying timestamps within the key
management protocols.
However, it is known [7] that each of the three key management schemes
has its subtle constraints and limitations:
- The symmetric key distribution protocol (MIKEY-PS) is simple
to implement but does not nicely scale in any larger configuration
of potential peer entities due to the need of mutually pre-assigned
shared master secrets.
Moreover, the security provided does not achieve the property of
perfect forward secrecy; i.e. compromise of the shared master
secret would render past and even future session keys susceptible
to compromise.
Further, the generation of the session key happens just at the
initiator. Thus, the responder has to fully trust the initiator
on choosing a good and secure session secret; the responder neither
is able to participate in the key generation nor to influence that
process. This is considered as a specific limitation in less
trusted environments.
- The public-key encryption scheme (MIKEY-PK) depends upon a
public-key infrastructure that certifies the private-public keys
by issuing and maintaining digital certificates. While such a key
management scheme provides full scalability in large networked
configurations, public-key infrastructures are still not widely
available and in general, implementations are significantly more
complex.
Further, additional round trips and computational processing might
be necessary for each end system in order to ascertain verification
of the digital certificates. For example, typical operations in
the context of a public-key infrastructure such as validating
digital certificates (RFC 3029, [31]), ascertaining the revocation
status of digital certificates (RFC 2560, [30]) and asserting
Euchner Expires - July 2005 [Page 4]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
certificate policies, construction of certification path(s)
([33]), requesting and obtaining necessary certificates (RFC 2511,
[32]) and management of certificates for such purposes ([29]) may
involve extra network communication handshakes with the public-key
infrastructure and with certification authorities and may
typically involve additional processing steps in the end systems.
Such steps and tasks all result in further delay of the key agreement
or key establishment phase among the end systems, negatively
impacting setup time. Any extra PKI handshakes and processing are
not in scope of MIKEY and since this document deploys symmetric
security mechanisms only, aspects of PKI, digital certificates and
related processing are not further covered in this document.
Finally, as in the symmetric case, the responder depends completely
upon the initiator choosing good and secure session keys.
- The third MIKEY-DHSIGN key management protocol deploys the
Diffie-Hellman key agreement scheme and authenticates the exchange
of the Diffie-Hellman half-keys in each direction by using a digital
signature. As in the previous method, this introduces the
dependency upon a public-key infrastructure with its strength on
scalability but also the limitations on computational costs in
performing the asymmetric long-integer operations and the
potential need for additional communication for verification of the
digital certificates.
However, the Diffie-Hellman key agreement protocol is known for its
subtle security strengths in that it is able to provide full perfect
forward secrecy (PFS) and further have both parties actively
involved in session key generation. This special security property
- despite the somewhat higher computational costs - makes
Diffie-Hellman techniques attractive in practice.
In order to overcome some of the limitations as outlined above, a special
need has been recognized for another efficient key agreement protocol
variant in MIKEY. This protocol variant aims to provide the capability
of perfect forward secrecy as part of a key agreement with low latency
without dependency on a public-key infrastructure.
Euchner Expires - July 2005 [Page 5]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
This document describes such a fourth light-weight key management scheme
for MIKEY that could somehow be seen as a synergetic optimization between
the pre-shared key distribution scheme and the Diffie-Hellman key
agreement.
The idea of that protocol is to apply the Diffie-Hellman key agreement
but instead of deploying a digital signature for authenticity of the
exchanged keying material rather uses a keyed-hash upon using
symmetrically pre-assigned shared secrets. This combination of security
mechanisms is called the HMAC-authenticated Diffie-Hellman (DH) key
agreement for MIKEY (DHHMAC).
The DHHMAC variant closely follows the design and philosophy of MIKEY and
reuses MIKEY protocol payload components and MIKEY mechanisms to its
maximum benefit and for best compatibility.
Like the MIKEY Diffie-Hellman protocol, DHHMAC does not scale beyond a
point-to-point constellation; thus, both MIKEY Diffie-Hellman protocols
do not support group-based keying for any group size larger than two
entities.
1.1. Definitions
The definitions and notations in this document are aligned with MIKEY,
see [3] and [3] sections 1.3 - 1.4.
All large integer computations in this document should be understood as
being mod p within some fixed group G for some large prime p; see [3] section
3.3; however, the DHHMAC protocol is applicable in general to other
appropriate finite, cyclical groups as well.
It is assumed that a pre-shared key s is known by both entities (initiator
and responder). The authentication key auth_key is derived from the
pre-shared secret s using the pseudo-random function PRF; see [3] sections
4.1.3 and 4.1.5.
In this text, [X] represents an optional piece of information. Generally
throughout the text, X SHOULD be present unless certain circumstance MAY
allow X being optional and not be present thereby resulting in weaker
Euchner Expires - July 2005 [Page 6]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
security potentially. Likewise [X, Y] represents an optional compound
piece of information where the pieces X and Y SHOULD be either both present
or MAY optionally be both absent. {X} denotes zero or more occurrences
of X.
1.2. Abbreviations
auth_key pre-shared authentication key, PRF-derived from
pre-shared key s.
DH Diffie-Hellman
DHi public Diffie-Hellman half key g^(xi) of the
Initiatior
DHr public Diffie-Hellman half key g^(xr) of the
Responder
DHHMAC HMAC-authenticated Diffie-Hellman
DoS Denial-of-service
G Diffie-Hellman group
HDR MIKEY common header payload
HMAC keyed Hash Message Authentication Code
HMAC-SHA1 HMAC using SHA1 as hash function (160-bit result)
IDi Identity of initiator
IDr Identity of receiver
IKE Internet Key Exchange
IPsec Internet Protocol Security
MIKEY Multimedia Internet KEYing
MIKEY-DHHMAC MIKEY Diffie-Hellman key management protocol using
HMAC
MIKEY-DHSIGN MIKEY Diffie-Hellman key agreement protocol
MIKEY-PK MIKEY public-key encryption-based key distribution
protocol
MIKEY-PS MIKEY pre-shared key distribution protocol
p Diffie-Hellman prime modulus
PKI Public-key Infrastructure
PRF MIKEY pseudo-random function (see [3] section
4.1.3.)
RSA Rivest, Shamir and Adleman
s pre-shared key
SDP Session Description Protocol
SOI Son-of-IKE, IKEv2
SP MIKEY Security Policy (Parameter) Payload
Euchner Expires - July 2005 [Page 7]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
T timestamp
TEK Traffic Encryption Key
TGK MIKEY TEK Generation Key as the common Diffie-
Hellman shared secret
TLS Transport Layer Security
xi secret, (pseudo) random Diffie-Hellman key of the
Initiator
xr secret, (pseudo) random Diffie-Hellman key of the
Responder
2. Scenario
The HMAC-authenticated Diffie-Hellman key agreement protocol (DHHMAC) for
MIKEY addresses the same scenarios and scope as the other three key
management schemes in MIKEY address.
DHHMAC is applicable in a peer-to-peer group where no access to a
public-key infrastructure can be assumed available. Rather, pre-shared
master secrets are assumed available among the entities in such an
environment.
In a pair-wise group, it is assumed that each client will be setting up
a session key for its outgoing links with it's peer using the DH-MAC key
agreement protocol.
As is the case for the other three MIKEY key management protocol, DHHMAC
assumes loosely synchronized clocks among the entities in the small group.
Note: To synchronize the clocks in a secure manner, some operational or
procedural means are recommended. However, MIKEY-DHHMAC does not describe
any secure time synchronization measures and leaves such tasks to the
discretion of the implementation. The reader is referred to [3] section
5.4 and [3] section 9.3 that give guidance on clock synchronization and
timestamps.
2.1. Applicability
Euchner Expires - July 2005 [Page 8]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
MIKEY-DHHMAC as well as the other MIKEY key management protocols are
optimized and targeted for the purpose of multimedia applications with
application-level key management needs under real-time session setup and
session management constraints.
As the MIKEY-DHHMAC key management protocol terminates in one roundtrip,
DHHMAC is applicable for integration into two-way handshake session- or
call signaling protocols such as
a) SIP/SDP (see [5]) where the encoded MIKEY messages are encapsulated
and transported in SDP containers of the SDP offer/answer handshake,
b) H.323 (see [22]) where the encoded MIKEY messages are transported in
the H.225.0 fast start call signaling handshake.
MIKEY-DHHMAC is offered as option to the other MIKEY key management
variants (MIKEY-pre-shared, MIKEY-public-key and MIKEY-DH-SIGN) for all
those cases where DHHMAC has its peculiar strengths (see section 5).
2.1.1. Usage in H.235
This section provides informative overview how MIKEY-DHHMAC can be
applied in some H.323-based multimedia environments. Generally, MIKEY
is applicable for multimedia applications including IP telephony. [22]
describes various use cases of the MIKEY key management protocols
(MIKEY-PS, MIKEY-PK, MIKEY-DHSIGN and MIKEY-DHHMAC) with the purpose to
establish TGK keying material among H.323 endpoints. The TGKs are then
used for media encryption by applying SRTP [27]. Addressed scenarios
include point-to-point with one or more intermediate gatekeepers (trusted
or partially trusted) in-between.
One particular use case addresses MIKEY-DHHMAC to establish a media
connection from an endpoint B calling (through a gatekeeper) to another
endpoint A that is located within that same gatekeeper zone. While EP-A
and EP-B typically do not share any auth_key a priori, some separate
protocol exchange means are achieved outside the actual call setup
procedure to establish an auth_key for the time while endpoints are being
registered with the gatekeeper; such protocols exist [22] but are not
shown in this document. The auth_key between the endpoints is being used
to authenticate and integrity protect the MIKEY-DHHMAC messages.
Euchner Expires - July 2005 [Page 9]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
To establish a call, it is assumed that endpoint B has obtained permission
from the gatekeeper (not shown). Endpoint B as the caller builds the
MIKEY-DHHMAC I_message(see section 3) and sends the I_message
encapsulated within the H.323-SETUP to endpoint A. A routing gatekeeper
(GK) would forward this message to endpoint B; in case of a non-routing
gatekeeper, endpoint B sends the SETUP directly to endpoint A. In either
case, H.323 inherent security mechanisms [28] are applied to protect the
(encapsulation) message during transfer. This is not depicted here. The
receiving endpoint A is able to verify the conveyed I_message and can
compute a TGK. Assuming that endpoint A would accept the call, EP-A then
builds the MIKEY-DHHMAC R_message and sends the response as part of the
CallProceeding-to-Connect message back to the calling endpoint B
(possibly through a routing gatekeeper). Endpoint B processes the
conveyed R_message to compute the same TGK as the called endpoint A.
1.) EP-B -> (GK) -> EP-A: SETUP(I_fwd_message [, I_rev_message])
2.) EP-A -> (GK) -> EP-B: CallProceeding-to-CONNECT(R_fwd_message [,
R_rev_message])
Notes: If it is necessary to establish directional TGKs for full-
duplex links in both directions B->A and A->B, then the calling
endpoint B instantiates the DHHMAC protocol twice: once in the
direction B->A using I_fwd_message and another run in parallel
in the direction A->B using I_rev_message. In that case, two
MIKEY-DHHMAC I_messages are encapsulated within SETUP
(I_fwd_message and I_rev_message) and two MIKEY-DHHMAC
R_messages (R_fwd_message and R_rev_message) are encapsulted
within CallProceeding-to-CONNECT. The I_rev_message
corresponds with the I_fwd_message.
Alternatively, the called endpoint A may instantiate the DHHMAC
protocol in a separate run with endpoint B (not shown); however,
this requires a third handshake to complete.
For more details on how the MIKEY protocols may be deployed with
H.235, please refer to [22].
2.2. Relation to GKMARCH
Euchner Expires - July 2005 [Page 10]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
The Group key management architecture (GKMARCH) [26] describes a
generic architecture for multicast security group key management
protocols. In the context of this architecture, MIKEY-DHHMAC may
operate as a registration protocol, see also [3] section 2.4. The main
entities involved in the architecture are a group controller/key server
(GCKS), the receiver(s), and the sender(s). Due to the pair-wise nature
of the Diffie-Hellman operation and the 1-roundtrip constraint, usage
of MIKEY-DHHMAC rules out any deployment as a group key management
protocol with more than two group entities. Only the degenerate case
with two peers is possible where for example the responder acts as the
group controller.
Note that MIKEY does not provide re-keying in the GKMARCH sense, only
updating of the keys by normal unicast messages.
3. DHHMAC Security Protocol
The following figure defines the security protocol for DHHMAC:
Initiator Responder
I_message = HDR, T, RAND, [IDi], IDr,
{SP}, DHi, KEMAC
-----------------------> R_message = HDR, T,
[IDr], IDi, DHr,
DHi, KEMAC
<----------------------
Figure 1: HMAC-authenticated Diffie-Hellman key based exchange,
where xi and xr are (pseudo) randomly chosen respectively
by the initiator and the responder.
The DHHMAC key exchange SHALL be done according to Figure 1. The
initiator chooses a (pseudo) random value xi, and sends an HMACed
message including g^(xi) and a timestamp to the responder. It is
recommended that the initiator SHOULD always include the identity
payloads IDi and IDr within the I_message; unless the receiver can defer
Euchner Expires - July 2005 [Page 11]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
the initiator's identity by some other means, then IDi MAY optionally
be omitted. The initiator SHALL always include the recipient's
identity.
The group parameters (e.g., the group G) are a set of parameters chosen
by the initiator. Note, that like in the MIKEY protocol, both sender
and receiver explicitly transmit the Diffie-Hellman group G within the
Diffie-Hellman payload DHi or DHr through an encoding (e.g., OAKELEY
group numbering, see [3] section 6.4); the actual group parameters g
and p however are not explicitly transmitted but can be deduced from
the Diffie-Hellman group G. The responder chooses a (pseudo) random
positive integer xr, and sends an HMACed message including g^(xr) and
the timestamp to the initiator. The responder SHALL always include the
initiator's identity IDi regardless of whether the I_message conveyed
any IDi. It is RECOMMENDED that the responder SHOULD always include
the identity payload IDr within the R_message; unless the initiator can
defer the reponder's identity by some other means, then IDr MAY
optionally be left out.
Both parties then calculate the TGK as g^(xi * xr).
The HMAC authentication provides authentication of the DH half-keys,
and is necessary to avoid man-in-the-middle attacks.
This approach is less expensive than digitally signed Diffie-Hellman.
It requires first of all, that both sides compute one exponentiation
and one HMAC, then one HMAC verification and finally another
Diffie-Hellman exponentiation.
With off-line pre-computation, the initial Diffie-Hellman half-key MAY
be computed before the key management transaction and thereby MAY
further reduce the overall round trip delay as well as reduce the risk
of denial-of-service attacks.
Processing of the TGK SHALL be accomplished as described in MIKEY [3]
chapter 4.
The computed HMAC result SHALL be conveyed in the KEMAC payload field
where the MAC fields holds the HMAC result. The HMAC SHALL be computed
Euchner Expires - July 2005 [Page 12]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
over the entire message excluding the MAC field using auth_key, see also
section 4.2.
3.1. TGK re-keying
TGK re-keying for DHHMAC generally proceeds as described in [3] section
4.5. Specifically, figure 2 provides the message exchange for the
DHHMAC update message.
Initiator Responder
I_message = HDR, T, [IDi], IDr,
{SP}, [DHi], KEMAC
-----------------------> R_message = HDR, T,
[IDr], IDi,
[DHr, DHi], KEMAC
<----------------------
Figure 2: DHHMAC update message
TGK re-keying supports two procedures:
a) True re-keying by exchanging new and fresh Diffie-Hellman
half-keys. For this, the initiator SHALL provide a new, fresh DHi
and the responder SHALL respond with a new, fresh DHr and the
received DHi.
b) Non-key related information update without any Diffie-Hellman
half-keys included in the exchange. Such transaction does not
change the actual TGK but updates other information like security
policy parameters for example. To only update the non-key related
information, [DHi] and [DHr, DHi] SHALL be left out.
Euchner Expires - July 2005 [Page 13]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
4. DHHMAC payload formats
This section specifies the payload formats and data type values for DHHMAC,
see also [3] chapter 6 for a definition of the MIKEY payloads.
This document does not define new payload formats but re-uses MIKEY
payloads for DHHMAC as referenced:
* Common header payload (HDR), see section 4.1 and [3] section 6.1
* SRTP ID sub-payload, see [3] section 6.1.1,
* Key data transport payload (KEMAC), see section 4.2 and [3] section
6.2
* DH data payload, see [3] section 6.4
* Timestamp payload, [3] section 6.6
* ID payload, [3] section 6.7
* Security Policy payload (SP), [3] section 6.10
* RAND payload (RAND), [3] section 6.11
* Error payload (ERR), [3] section 6.12
* General Extension Payload, [3] section 6.15
4.1. Common header payload (HDR)
Referring to [3] section 6.1, for DHHMAC the following data types SHALL
be used:
Data type | Value | Comment
-------------------------------------------------------------
DHHMAC init | 7 | Initiator's DHHMAC exchange message
DHHMAC resp | 8 | Responder's DHHMAC exchange message
Error | 6 | Error message, see [3] section 6.12
Euchner Expires - July 2005 [Page 14]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
Table 4.1.a
Note: A responder is able to recognize the MIKEY DHHMAC protocol by
evaluating the data type field as 7 or 8. This is how the responder
can differentiate between MIKEY and MIKEY DHHMAC.
The next payload field SHALL be one of the following values:
Next payload| Value | Section
----------------------------------------------------------------
Last payload| 0 | -
KEMAC | 1 | section 4.2 and [3] section 6.2
DH | 3 | [3] section 6.4
T | 5 | [3] section 6.6
ID | 6 | [3] section 6.7
SP | 10 | [3] section 6.10
RAND | 11 | [3] section 6.11
ERR | 12 | [3] section 6.12
General Ext.| 21 | [3] section 6.15
Table 4.1.b
Other defined next payload values defined in [3] SHALL not be applied
to DHHMAC.
The responder in case of a decoding error or of a failed HMAC
authentication verification SHALL apply the Error payload data type.
4.2. Key data transport payload (KEMAC)
DHHMAC SHALL apply this payload for conveying the HMAC result along with
the indicated authentication algorithm. KEMAC when used in conjunction
with DHHMAC SHALL not convey any encrypted data; thus Encr alg SHALL
be set to 2 (NULL), Encr data len SHALL be set to 0 and Encr data SHALL
be left empty. The AES key wrap method (see [23]) SHALL not be applied
for DHHMAC.
For DHHMAC, this key data transport payload SHALL be the last payload
in the message. Note that the Next payload field SHALL be set to Last
Euchner Expires - July 2005 [Page 15]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
payload. The HMAC is then calculated over the entire MIKEY message
excluding the MAC field using auth_key as described in [3] section 5.2
and then stored within MAC field.
MAC alg | Value | Comments
------------------------------------------------------------------
HMAC-SHA-1 | 0 | Mandatory, Default (see [4])
NULL | 1 | Very restricted use, see
| [3] section 4.2.4
Table 4.2.a
HMAC-SHA-1 is the default hash function that MUST be implemented as part
of the DHHMAC. The length of the HMAC-SHA-1 result is 160 bits.
4.3. ID payload (ID)
For DHHMAC, this payload SHALL only hold a non-certificate based
identity.
4.4. General Extension Payload
For DHHMAC and to avoid bidding-down attacks, this payload SHALL list
all key management protocol identifiers of a surrounding encapsulation
protocol such as for example, SDP [5]. The General Extension Payload
SHALL be integrity-protected with the HMAC using the shared secret.
Type | Value | Comments
SDP IDs | 1 | List of SDP key management IDs (allocated for
use in [5]); see also [3] section 6.15.
Table 4.4.a
5. Security Considerations
This document addresses key management security issues throughout. For
a comprehensive explanation of MIKEY security considerations, please
refer to MIKEY [3] section 9.
Euchner Expires - July 2005 [Page 16]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
In addition to that, this document addresses security issues according
to [8] where the following security considerations apply in particular
to this document:
5.1. Security environment
Generally, the DHHMAC security protocol described in this document focuses
primarily on communication security; i.e. the security issues concerned
with the MIKEY DHHMAC protocol. Nevertheless, some system security issues
are of interest as well that are not explicitly defined by the DHHMAC
protocol, but should be provided locally in practice.
The system that runs the DHHMAC protocol entity SHALL provide the
capability to generate (pseudo) random numbers as input to the
Diffie-Hellman operation (see [9], [15]). Furthermore, the system SHALL
be capable of storing the generated (pseudo) random data, secret data,
keys and other secret security parameters securely (i.e. confidential and
safe from unauthorized tampering).
5.2. Threat model
The threat model that this document adheres to cover the issues of
end-to-end security in the Internet generally; without ruling out the
possibility that MIKEY DHHMAC be deployed in a corporate, closed IP
environment. This also includes the possibility that MIKEY DHHMAC be
deployed on a hop-by-hop basis with some intermediate trusted "MIKEY
DHHMAC proxies" involved.
Since DHHMAC is a key management protocol, the following security threats
are of concern:
* Unauthorized interception of plain TGKs.
For DHHMAC this threat does not occur since the TGK is not actually
transmitted on the wire (not even in encrypted fashion).
* Eavesdropping of other, transmitted keying information:
DHHMAC protocol does not explicitly transmit the TGK at all. Rather,
by the Diffie-Hellman "encryption" operation, that conceals the secret
(pseudo) random values, only partial information (i.e. the DH- half key)
for construction of the TGK is transmitted. It is fundamentally assumed
Euchner Expires - July 2005 [Page 17]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
that availability of such Diffie-Hellman half-keys to an eavesdropper
does not result in any substantial security risk; see 5.4. Furthermore,
the DHHMAC carries other data such as timestamps, (pseudo) random
values, identification information or security policy parameters;
eavesdropping of any such data is considered not to yield any significant
security risk.
* Masquerade of either entity:
This security threat must be avoided and if a masquerade attack would
be attempted, appropriate detection means must be in place. DHHMAC
addresses this threat by providing mutual peer entity authentication.
* Man-in-the-middle attacks:
Such attacks threaten the security of exchanged, non-authenticated
messages. Man-in-the-middle attacks usually come with masquerade and
or loss of message integrity (see below). Man-in-the-middle attacks
must be avoided, and if present or attempted must be detected
appropriately. DHHMAC addresses this threat by providing mutual peer
entity authentication and message integrity.
* Loss of integrity:
This security threat relates to unauthorized replay, deletion,
insertion and manipulation of messages. While any such attacks cannot
be avoided they must be detected at least. DHHMAC addresses this threat
by providing message integrity.
* Bidding-down attacks:
When multiple key management protocols each of a distinct security level
are offered (e.g., such as is possible by SDP [5]), avoiding
bidding-down attacks is of concern. DHHMAC addresses this threat by
reusing the MIKEY General Extension Payload mechanism, where all key
management protocol identifiers are be listed within the MIKEY General
Extension Payload.
Some potential threats are not within the scope of this threat model:
* Passive and off-line cryptanalysis of the Diffie-Hellman algorithm:
Under certain reasonable assumptions (see 5.4 below) it is widely
believed that DHHMAC is sufficiently secure and that such attacks be
Euchner Expires - July 2005 [Page 18]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
infeasible although the possibility of a successful attack cannot be
ruled out completely.
* Non-repudiation of the receipt or of the origin of the message:
These are not requirements of this environment and thus related
countermeasures are not provided at all.
* Denial-of-service or distributed denial-of-service attacks:
Some considerations are given on some of those attacks, but DHHMAC does
not claim to provide full countermeasure against any of those attacks.
For example, stressing the availability of the entities are not thwarted
by means of the key management protocol; some other local
countermeasures should be applied. Further, some DoS attacks are not
countered such as interception of a valid DH-request and its massive
instant duplication. Such attacks might at least be countered partially
by some local means that are outside the scope of this document.
* Identity protection:
Like MIKEY, identity protection is not a major design requirement for
MIKEY-DHHMAC either, see [3]. No security protocol is known so far,
that is able to provide the objectives of DHHMAC as stated in section
5.3 including identity protection within just a single roundtrip.
MIKEY-DHHMAC trades identity protection for better security for the
keying material and shorter roundtrip time. Thus, MIKEY-DHHMAC does not
provide identity protection on its own but may inherit such property
from a security protocol underneath that actually features identity
protection. On the other hand, it is expected that MIKEY-DHHMAC is
typically being deployed within SDP/SIP ([20], [5]); both those
protocols do not provide end-to-end identity protection either.
The DHHMAC security protocol (see section 3) and the TGK re-keying
security protocol (see section 3.1) provide the option not to supply
identity information. This option is only applicable if some other means
are available of supplying trustworthy identity information; e.g., by
relying on secured links underneath of MIKEY that supply trustworthy
identity information otherwise. However, it is understood that without
identity information present, the MIKEY key management security
protocols might be subject to security weaknesses such as masquerade,
impersonation and reflection attacks particularly in end-to-end
scenarios where no other secure means of assured identity information
is provided.
Euchner Expires - July 2005 [Page 19]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
Leaving identity fields optional if possible thus should not be seen
as a privacy method either, but rather as a protocol optimization
feature.
5.3. Security features and properties
With the security threats in mind, this draft provides the following
security features and yields the following properties:
* Secure key agreement with the establishment of a TGK at both peers:
This is achieved using an authenticated Diffie-Hellman key management
protocol.
* Peer-entity authentication (mutual):
This authentication corroborates that the host/user is authentic in that
possession of a pre-assigned secret key is proven using keyed HMAC.
Authentication occurs on the request and on the response message, thus
authentication is mutual.
The HMAC computation corroborates for authentication and message
integrity of the exchanged Diffie-Hellman half-keys and associated
messages. The authentication is absolutely necessary in order to avoid
man-in-the-middle attacks on the exchanged messages in transit and in
particular, on the otherwise non-authenticated exchanged
Diffie-Hellman half keys.
Note: This document does not address issues regarding authorization;
this feature is not provided explicitly. However, DHHMAC authentication
means support and facilitate realization of authorization means (local
issue).
* Cryptographic integrity check:
The cryptographic integrity check is achieved using a message digest
(keyed HMAC). It includes the exchanged Diffie-Hellman half-keys but
covers the other parts of the exchanged message as well. Both mutual
peer entity authentication and message integrity provide effective
countermeasure against man-in-the-middle attacks.
Euchner Expires - July 2005 [Page 20]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
The initiator may deploy a local timer that fires when the awaited
response message did not arrive timely. This is to detect deletion of
entire messages.
* Replay protection of the messages is achieved using embedded
timestamps. In order to detect replayed messages it is essential that
the clocks among initiator and sender be roughly synchronized. The
reader is referred to [3] section 5.4 and [3] section 9.3 that provide
further considerations and give guidance on clock synchronization and
timestamp usage. Should the clock synchronization be lost, then end
systems cannot detect replayed messages anymore resulting that the end
systems cannot securely establish keying material. This may result in
a denial-of-service, see [3] section 9.5.
* Limited DoS protection:
Rapid checking of the message digest allows verifying the authenticity
and integrity of a message before launching CPU intensive Diffie-Hellman
operations or starting other resource consuming tasks. This protects
against some denial-of-service attacks: malicious modification of
messages and spam attacks with (replayed or masqueraded) messages.
DHHMAC probably does not explicitly counter sophisticated distributed,
large-scale denial-of-service attacks that compromise system
availability for example. Some DoS protection is provided by inclusion
of the initiator's identity payload in the I_message. This allows the
recipient to filter out those (replayed) I_messages that are not
targeted for him and avoids the recipient from creating unnecessary
MIKEY sessions.
* Perfect-forward secrecy (PFS):
Other than the MIKEY pre-shared and public-key based key distribution
protocols, the Diffie-Hellman key agreement protocol features a
security property called perfect forward secrecy. That is, that even
if the long-term pre-shared key would be compromised at some point in
time, this would not render past or future session keys compromised.
Neither the MIKEY pre-shared nor the MIKEY public-key protocol variants
are able to provide the security property of perfect-forward secrecy.
Thus, none of the other MIKEY protocols is able to substitute the
Diffie-Hellman PFS property.
Euchner Expires - July 2005 [Page 21]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
As such, DHHMAC but also digitally signed DH provides a far superior
security level over the pre-shared or public-key based key distribution
protocol in that respect.
* Fair, mutual key contribution:
The Diffie-Hellman key management protocol is not a strict key
distribution protocol per se with the initiator distributing a key to
its peers. Actually, both parties involved in the protocol exchange
are able to equally contribute to the common Diffie-Hellman TEK traffic
generating key. This reduces the risk of either party cheating or
unintentionally generating a weak session key. This makes the DHHMAC
a fair key agreement protocol. One may view this property as an
additional distributed security measure that is increasing security
robustness over the case where all the security depends just on the
proper implementation of a single entity.
In order for Diffie-Hellman key agreement to be secure, each party SHALL
generate its xi or xr values using a strong, unpredictable pseudo-random
generator if a source of true randomness is not available. Further,
these values xi or xr SHALL be kept private. It is RECOMMENDED that
these secret values be destroyed once the common Diffie-Hellman shared
secret key has been established.
* Efficiency and performance:
Like the MIKEY-public key protocol, the MIKEY DHHMAC key agreement
protocol securely establishes a TGK within just one roundtrip. Other
existing key management techniques like IPsec-IKE [14], IPsec-IKEv2
[21] and TLS [13] and other schemes are not deemed adequate in addressing
sufficiently those real-time and security requirements; they all use
more than a single roundtrip. All the MIKEY key management protocols
are able to complete their task of security policy parameter negotiation
including key-agreement or key distribution in one roundtrip. However,
the MIKEY pre-shared and the MIKEY public-key protocol both are able
to complete their task even in a half-round trip when the confirmation
messages are omitted.
Using HMAC in conjunction with a strong one-way hash function such as
SHA1 may be achieved more efficiently in software than expensive
public-key operations. This yields a particular performance benefit
of DHHMAC over signed DH or the public-key encryption protocol.
Euchner Expires - July 2005 [Page 22]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
If a very high security level is desired for long-term secrecy of the
negotiated Diffie-Hellman shared secret, longer hash values may be
deployed such as SHA256, SHA384 or SHA512 provide, possibly in
conjunction with stronger Diffie-Hellman groups. This is left as for
further study.
For the sake of improved performance and reduced round trip delay either
party may off-line pre-compute its public Diffie-Hellman half-key.
On the other side and under reasonable conditions, DHHMAC consumes more
CPU cycles than the MIKEY pre-shared key distribution protocol. The
same might hold true quite likely for the MIKEY public-key distribution
protocol (depending on choice of the private and public key lengths).
As such, it can be said that DHHMAC provides sound performance when
compared with the other MIKEY protocol variants.
The use of optional identity information (with the constraints stated
in section 5.2) and optional Diffie-Hellman half-key fields provides
a means to increase performance and shorten the consumed network
bandwidth.
* Security infrastructure:
This document describes the HMAC-authenticated Diffie-Hellman key
agreement protocol that completely avoids digital signatures and the
associated public-key infrastructure as would be necessary for the X.509
RSA public-key based key distribution protocol or the digitally signed
Diffie-Hellman key agreement protocol as described in MIKEY. Public-key
infrastructures may not always be available in certain environments nor
may they be deemed adequate for real-time multimedia applications when
taking additional steps for certificate validation and certificate
revocation methods with additional round-trips into account.
DHHMAC does not depend on PKI nor do implementations require PKI
standards and thus is believed to be much simpler than the more complex
PKI facilities.
DHHMAC is particularly attractive in those environments where
provisioning of a pre-shared key has already been accomplished.
* NAT-friendliness:
Euchner Expires - July 2005 [Page 23]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
DHHMAC is able to operate smoothly through firewall/NAT devices as long
as the protected identity information of the end entity is not an IP
/transport address.
* Scalability:
Like the MIKEY signed Diffie-Hellman protocol, DHHMAC does not scale
to any larger configurations beyond peer-to-peer groups.
5.4. Assumptions
This document states a couple of assumptions upon which the security of
DHHMAC significantly depends. It is assumed, that
* the parameters xi, xr, s and auth_key are to be kept secret.
* the pre-shared key s has sufficient entropy and cannot be
effectively guessed.
* the pseudo-random function (PRF) is secure, yields indeed the
pseudo-random property and maintains the entropy.
* a sufficiently large and secure Diffie-Hellman group is applied.
* the Diffie-Hellman assumption holds saying basically that even with
knowledge of the exchanged Diffie-Hellman half-keys and knowledge of
the Diffie-Hellman group, it is infeasible to compute the TGK or to
derive the secret parameters xi or xr. The latter is also called the
discrete logarithm assumption. Please see [7], [11] or [12] for more
background information regarding the Diffie-Hellman problem and its
computational complexity assumptions.
* the hash function (SHA1) is secure; i.e. that it is computationally
infeasible to find a message which corresponds to a given message digest,
or to find two different messages that produce the same message digest.
* the HMAC algorithm is secure and does not leak the auth_key. In
particular, the security depends on the message authentication property
of the compression function of the hash function H when applied to single
blocks (see [6]).
Euchner Expires - July 2005 [Page 24]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
* a source capable of producing sufficiently many bits of (pseudo)
randomness is available.
* the system upon which DHHMAC runs is sufficiently secure.
5.5. Residual risk
Although these detailed assumptions are non-negligible, security experts
generally believe that all these assumptions are reasonable and that the
assumptions made can be fulfilled in practice with little or no expenses.
The mathematical and cryptographic assumptions upon the properties of the
PRF, the Diffie-Hellman algorithm (discrete log-assumption), the HMAC and
SHA1 algorithms have not been proved yet nor have they been disproved by
the time of this writing.
Thus, a certain residual risk remains, which might threaten the overall
security at some unforeseeable time in the future.
The DHHMAC would be compromised as soon as any of the listed assumptions
do not hold anymore.
The Diffie-Hellman mechanism is a generic security technique that is not
only applicable to groups of prime order or of characteristic two. This
is because of the fundamental mathematical assumption that the discrete
logarithm problem is also a very hard one in general groups. This enables
Diffie-Hellman to be deployed also for GF(p)*, for sub-groups of
sufficient size and for groups upon elliptic curves. RSA does not allow
such generalization, as the core mathematical problem is a different one
(large integer factorization).
RSA asymmetric keys tend to become increasingly lengthy (1536 bits and
more) and thus very computational intensive. Neverthess, elliptic curve
Diffie-Hellman (ECDH) allows to cut-down key lengths substantially (say
170 bits or more) while maintaining at least the security level and
providing even significant performance benefits in practice. Moreover,
it is believed that elliptic curve techniques provide much better
protection against side channel attacks due to the inherent redundancy
in the projective coordinates. For all these reasons, one may view
elliptic-curve-based Diffie-Hellman as being more "future-proof" and
Euchner Expires - July 2005 [Page 25]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
robust against potential threats than RSA. Note, that an elliptic-curve
Diffie-Hellman variant of MIKEY remains for further study.
It is not recommended to deploy DHHMAC for any other usage than depicted
in section 2. Otherwise any such misapplication might lead to unknown,
undefined properties.
5.6. Authorization and Trust Model
Basically, similar remarks on authorization as stated in [3] section
4.3.2. hold also for DHHMAC. However, as noted before, this key management
protocol does not serve full groups.
One may view the pre-established shared secret to yield some
pre-established trust relationship between the initiator and the
responder. This results in a much simpler trust model for DHHMAC than
would be the case for some generic group key management protocol and
potential group entities without any pre-defined trust relationship. The
common group controller in conjunction with the assumption of a shared
key simplifies the communication setup of the entities.
One may view the pre-established trust relationship through the pre-shared
secret as some means for pre-granted, implied authorization. This
document does not define any particular authorization means but leaves
this subject to the application.
6. Acknowledgments
This document incorporates kindly valuable review feedback from Steffen
Fries, Hannes Tschofenig, Fredrick Lindholm and Russell Housley and
general feedback by the MSEC WG.
Conclusions
Key management for environments and applications with real-time and
performance constraints are becoming of interest. Existing key management
techniques like IPsec-IKE [14] and IPsec-IKEv2 [22], TLS [13] and other
Euchner Expires - July 2005 [Page 26]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
schemes are not deemed adequate in addressing sufficiently those real-time
and security requirements.
MIKEY defines three key management security protocols addressing
real-time constraints. DHHMAC as described in this document defines a
fourth MIKEY variant aiming at the same target.
While each of the four key management protocols has its own merits there
are also certain limitations of each approach. As such there is no single
ideal solution and none of the variants is able to subsume the other
remaining variants.
It is concluded that DHHMAC features useful security and performance
properties that none of the other three MIKEY variants is able to provide.
7. IANA considerations
This document does not define its own new name spaces for DHHMAC, beyond
the IANA name spaces that have been assigned for MIKEY, see [3] section
10 and section 10.1.
The name spaces for the following fields in the Common header payload (from
Section 4.1) are requested to be managed by IANA (in bracket is the
reference to the table with the initially registered values):
* data type (Table 4.1.a); to be aligned with [3] table 6.1.a.
8. References
8.1 Normative References
[1] Bradner, S., "The Internet Standards Process -- Revision 3",
BCP 9, RFC 2026, October 1996.
[2] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[3] J. Arkko, E. Carrara, F. Lindholm, M. Naslund, K. Norrman;
"MIKEY: Multimedia Internet KEYing", RFC 3830 IETF, August 2004.
Euchner Expires - July 2005 [Page 27]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
[4] NIST, FIBS-PUB 180-1, "Secure Hash Standard", April 1995,
http://csrc.nist.gov/fips/fip180-1.ps.
[5] J. Arkko, E. Carrara et al: "Key Management Extensions for SDP
and RTSP", Internet Draft <draft-ietf-mmusic-kmgmt-ext-11.txt>,
Work in Progress (MMUSIC WG), IETF, April 2004.
[6] H. Krawczyk, M. Bellare, R. Canetti: "HMAC: Keyed-Hashing for
Message Authentication", RFC 2104, February 1997.
8.2 Informative References
[7] A.J. Menezes, P. van Oorschot, S. A. Vanstone: "Handbook of
Applied Cryptography", CRC Press 1996.
[8] E. Rescorla, B. Korver: " Guidelines for Writing RFC Text on
Security Considerations", RFC 3552, IETF, July 2003.
[9] D. Eastlake, S. Crocker: "Randomness Recommendations for
Security", RFC 1750, IETF, December 1994.
[10] S.M. Bellovin, C. Kaufman, J. I. Schiller: "Security
Mechanisms for the Internet", RFC 3631, IETF, December 2003.
[11] Ueli M. Maurer, S. Wolf: "The Diffie-Hellman Protocol",
Designs, Codes, and Cryptography, Special Issue Public Key
Cryptography, Kluwer Academic Publishers, vol. 19, pp. 147-171,
2000. ftp://ftp.inf.ethz.ch/pub/crypto/publications/MauWol00c.ps
[12] Discrete Logarithms and the Diffie-Hellman Protocol;
http://www.crypto.ethz.ch/research/ntc/dldh/
[13] T. Dierks, C. Allen: "The TLS Protocol Version 1.0.", RFC 2246,
IETF, January 1999.
[14] D. Harkins, D. Carrel: "The Internet Key Exchange (IKE).", RFC
2409, IETF, November 1998.
[15] Donald E. Eastlake, Jeffrey I. Schiller, Steve Crocker:
Euchner Expires - July 2005 [Page 28]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
"Randomness Requirements for Security";
<draft-eastlake-randomness2-10.txt>; Work in Progress, IETF,
January 2005.
[16] J. Schiller: "Strong Security Requirements for Internet
Engineering Task Force Standard Protocols", RFC 3365, IETF, 2002.
[17] C. Meadows: "Advice on Writing an Internet Draft Amenable to
Security Analysis", Work in Progress,
<draft-irtf-cfrg-advice-00.txt>, IRTF, October 2002.
[18] T. Narten: "Guidelines for Writing an IANA Considerations
Section in RFCs", RFC 2434, IETF, October 1998.
[19] J. Reynolds: "Instructions to Request for Comments (RFC)
Authors", Work in Progress, <draft-rfc-editor-rfc2223bis-08.txt>,
IETF, August 2004.
[20] J. Rosenberg et all: "SIP: Session Initiation Protocol", RFC
3261, IETF, June 2002.
[21] Ch. Kaufman: "Internet Key Exchange (IKEv2) Protocol", Work in
Progress (IPSEC WG), <draft-ietf-ipsec-ikev2-17.txt>, Internet
Draft, Work in Progress (IPSEC WG).
[22] ITU-T Recommendation H.235 Annex G: "Usage of the MIKEY
Key Management Protocol for the Secure Real Time Transport Protocol
(SRTP) within H.235"; 1/2005.
[23] Schaad, J., Housley R.: "Advanced Encryption Standard (AES)
Key Wrap Algorithm", RFC 3394, IETF, September 2002.
[24] Baugher, M., Weis, B., Hardjono, T., Harney, H.: "The Group
Domain of Interpretation", RFC 3547, IETF, July 2003.
[25] Harney, H., Colegrove, A., Harder, E., Meth, U., Fleischer, R.:
"Group Secure Association Key Management Protocol",
<draft-ietf-msec-gsakmp-sec-07.txt>, Internet Draft, Work in
Progress (MSEC WG).
[26] Baugher, M., Canetti, R., Dondeti, L., and Lindholm, F.: "Group
Euchner Expires - July 2005 [Page 29]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
Key Management Architecture", <draft-ietf-msec-gkmarch-08.txt>,
Internet Draft, Work in Progress (MSEC WG).
[27] Baugher, McGrew, Oran, Blom, Carrara, Naslund: "The Secure Real-time
Transport Protocol", RFC 3711, IETF, March 2004.
[28] ITU-T Recommendation H.235V3Amd1 Corr1, "Security and encryption for
H-series (H.323 and other H.245-based) multimedia terminals",
(01/2005).
[29] C. Adams et al: "Internet X.509 Public Key Infrastructure Certificate
Management Protocols"; draft-ietf-pkix-rfc2510bis-09.txt,
Internet Draft, Work in Progress (PKIX WG).
[30] M. Myers et al: "X.509 Internet Public Key Infrastructure Online
Certificate Status Protocol - OCSP", RFC 2560, IETF, June 1999.
[31] C. Adams et al: "Internet X.509 Public Key Infrastructure Data
Validation and Certification Server Protocols", RFC 3029, IETF,
February 2001.
[32] M. Myers: "Internet X.509 Certificate Request Message Format", RFC
2511, IETF, March 1999.
[33] M. Cooper et al: "Internet X.509 Public Key Infrastructure:
Certification Path Building",
<draft-ietf-pkix-certpathbuild-05.txt>, Internet Draft, Work in
Progress (PKIX WG).
[34] Bradner, S., "IETF Rights in Contributions", BCP 78, RFC 3667,
February 2004.
[35] Bradner, S., "Intellectual Property Rights in IETF Technology", BCP
79, RFC 3668, February 2004.
Full Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject to
the rights, licenses and restrictions contained in BCP 78, and except as
set forth therein, the authors retain all their rights.
Euchner Expires - July 2005 [Page 30]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
This document and the information contained herein are provided on an "AS
IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS
SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property Rights
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in this
document or the extent to which any license under such rights might or
might not be available; nor does it represent that it has made any
independent effort to identify any such rights. Information on the
procedures with respect to rights in ISOC Documents can be found in BCP
78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any assurances
of licenses to be made available, or the result of an attempt made to obtain
a general license or permission for the use of such proprietary rights
by implementers or users of this specification can be obtained from the
IETF on-line IPR repository at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary rights
that may cover technology that may be required to implement this standard.
Please address the information to the IETF at
ietf-ipr@ietf.org.
Expiration Date
This Internet Draft expires on 30 July 2005.
Euchner Expires - July 2005 [Page 31]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
[Note to the RFC editor: Please remove the entire following section prior
to publication.]
Revision History
Changes against draft-ietf-msec-mikey-dhhmac-08.txt:
* PKIX removed; some minor editorials.
Changes against draft-ietf-msec-mikey-dhhmac-07.txt:
* Feedback addressed from AD review.
* added considerations on the possible impact of PKIX protocols and
operations to end systems with real-time constraints (section 1).
* added note that DH group is transmitted explicitly but not the parameters
g and p; see section 3.
* added considerations on clock synchronization and timestamps in section
2 and in section 5.3 in the view of consequences on replay protection.
* references updated.
* editorial corrections and cleanup.
Changes against draft-ietf-msec-mikey-dhhmac-06.txt:
* Abstract reworded.
* used new RFC boilerplate: changed/moved IPR statement (now at the
beginning), status of Memo, and Intellectual Property Rights section
in accordance with RFC 3667, RFC 3668.
* ID nits removal.
* References updated.
* Note added to section 4.1 explaining how to differentiate between
MIKEY and DHHMAC.
* New section 4.4 added that describes the use of the general extension
payload to avoid bidding-down attacks.
* Description of the bidding-down avoidance mechanism removed from the
threat model in section 5.2.
* IANA considerations section re-written and aligned with MIKEY.
* Open issue on KMID pointed in IANA considerations section.
* editorial clean-up.
Changes against draft-ietf-msec-mikey-dhhmac-05.txt:
Euchner Expires - July 2005 [Page 32]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
* HMAC-SHA1-96 option removed (see section 1.2, 4.2, 5.3,). This
option does not really provide much gain; removal reduces number
of options.
* IDr added to I_message for DoS protection of the recipient; see
section 3, 3.1, 5.3.
* References updated.
Changes against draft-ietf-msec-mikey-dhhmac-04.txt:
* Introduction section modified: PFS property of DH, requirement for
4th MIKEY key management variant motivated.
* MIKEY-DHSIGN, MIKEY-PK and MIKEY-PS added to section 1.2
Abbreviations.
* Note on secure time synchronization added to section 2.0.
* New section 2.2 "Relation to GMKARCH" added.
* New section 2.1.1 "Usage in H.235" added: this section outlines a use
case of DHHMAC in the context of H.235.
* Trade-off between identity-protection and security & performance
added to section 5.1.
* New section 5.6 "Authorization and Trust Model" added.
* Some further informative references added.
Changes against draft-ietf-msec-mikey-dhhmac-03.txt:
* RFC 3552 available; some references updated.
Changes against draft-ietf-msec-mikey-dhhmac-02.txt:
* text allows both random and pseudo-random values.
* exponentiation ** changed to ^.
* Notation aligned with MIKEY-07.
* Clarified that the HMAC is calculated over the entire MIKEY
message excluding the MAC field.
* Section 4.2: The AES key wrap method SHALL not be applied.
* Section 1: Relationship with other, existing work mentioned.
Changes against draft-ietf-msec-mikey-dhhmac-01.txt:
* bidding-down attacks addressed (see section 5.2).
Euchner Expires - July 2005 [Page 33]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
* optional [X], [X, Y] defined and clarified (see section 1.1,
5.3).
* combination of options defined in key update procedure (see
section 3.1).
* ID payloads clarified (see section 3 and 5.2).
* relationship with MIKEY explained (roundtrip, performance).
* new section 2.1 on applicability of DHHMAC for SIP/SDP and
H.323 added.
* more text due to DH resolution incorporated in section 5.3
regarding PFS, security robustness of DH, generalization
capability of DH to general groups in particular EC and
"future-proofness".
* a few editorials and nits.
* references adjusted and cleaned-up.
Changes against draft-ietf-msec-mikey-dhhmac-00.txt:
* category set to proposed standard.
* identity protection clarified.
* aligned with MIKEY-05 DH protocol, notation and with payload
* some editorials and nits.
Changes against draft-euchner-mikey-dhhmac-00.txt:
* made a MSEC WG draft
* aligned with MIKEY-03 DH protocol, notation and with payload
formats
* clarified that truncated HMAC actually truncates the HMAC result
rather than the SHA1 intermediate value.
* improved security considerations section completely rewritten in
the spirit of [8].
* IANA consideration section added
* a few editorial improvements and corrections
* IPR clarified and IPR section changed.
Author's Addresses
Martin Euchner
Euchner Expires - July 2005 [Page 34]
HMAC-authenticated Diffie-Hellman for MIKEY January 2005
Email: martin_euchner@hotmail.com
Phone: +49 89 722 55790 Hofmannstr. 51
Fax: +49 89 722 62366
81359 Munich, Germany
Euchner Expires - July 2005 [Page 35]
| PAFTECH AB 2003-2026 | 2026-04-22 23:28:43 |