One document matched: draft-ietf-dnsext-dnssec-rsasha256-10.xml
<?xml version="1.0"?>
<?rfc toc="yes"?>
<?rfc compact="yes"?>
<?rfc strict="yes"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
<rfc ipr="trust200811"
category="std"
docName="draft-ietf-dnsext-dnssec-rsasha256-10">
<front>
<title abbrev="DNSSEC RSA/SHA-2">Use of SHA-2 algorithms with RSA in DNSKEY and RRSIG Resource Records for DNSSEC</title>
<author initials="J.R.P." surname="Jansen"
fullname="Jelte Jansen">
<organization>NLnet Labs</organization>
<address>
<postal>
<street>Kruislaan 419</street>
<city>Amsterdam</city>
<code>1098VA</code>
<country>NL</country>
</postal>
<email>jelte@NLnetLabs.nl</email>
<uri>http://www.nlnetlabs.nl/</uri>
</address>
</author>
<date day="08" month="January" year="2009" />
<area>General</area>
<workgroup>DNS Extensions working group</workgroup>
<keyword>RFC</keyword>
<keyword>Request for Comments</keyword>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<keyword>DNSSEC</keyword>
<keyword>RSA</keyword>
<keyword>SHA-256</keyword>
<keyword>SHA-512</keyword>
<abstract>
<t>
This document describes how to produce RSA/SHA-256
and RSA/SHA-512 DNSKEY and RRSIG resource records for
use in the Domain Name System Security Extensions
(DNSSEC, RFC 4033, RFC 4034, and RFC 4035).
</t>
</abstract>
</front>
<middle>
<section anchor="intro" title="Introduction">
<t>
The Domain Name System (DNS) is the global hierarchical
distributed database for Internet Naming. The
DNS has been extended to use cryptographic keys
and digital signatures for the verification of the
authenticity and integrity of its data. RFC 4033 <xref
target="RFC4033"/>, RFC 4034 <xref target="RFC4034"/>,
and RFC 4035 <xref target="RFC4035"/> describe these
DNS Security Extensions, called DNSSEC.
</t> <t>
RFC 4034 describes how to store DNSKEY and RRSIG
resource records, and specifies a list of cryptographic
algorithms to use. This document extends that list
with the algorithms RSA/SHA-256 and RSA/SHA-512, and
specifies how to store DNSKEY data and how to produce
RRSIG resource records with these hash algorithms.
</t> <t>
Familiarity with DNSSEC, RSA and the SHA-2 <xref
target="FIPS.180-3.2008" /> family of algorithms is
assumed in this document.
</t> <t>
To refer to both SHA-256 and SHA-512, this document
will use the name SHA-2. This is done to improve
readability. When a part of text is specific for
either SHA-256 or SHA-512, their specific names are
used. The same goes for RSA/SHA-256 and RSA/SHA-512,
which will be grouped using the name RSA/SHA-2.
</t>
<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 <xref target="RFC2119"/>.
</t>
</section>
<section anchor="dnskey" title="DNSKEY Resource Records">
<t>
The format of the DNSKEY RR can be found in RFC 4034 <xref
target="RFC4034"/>. RFC 3110 <xref target="RFC3110"/>
describes the use of RSA/SHA-1 for DNSSEC signatures.
</t>
<section anchor="dnskey-rsasha256" title="RSA/SHA-256 DNSKEY Resource Records">
<t>
RSA public keys for use with RSA/SHA-256 are stored
in DNSKEY resource records (RRs) with the algorithm
number {TBA1}.
</t>
<t>
For interoperability, as in RFC 3110
<xref target="RFC3110"/>, the key size of RSA/SHA-256
keys MUST NOT be less than 512 bits, and MUST NOT be
more than 4096 bits.
</t>
</section>
<section anchor="dnskey-rsasha512" title="RSA/SHA-512 DNSKEY Resource Records">
<t>
RSA public keys for use with RSA/SHA-512 are stored
in DNSKEY resource records (RRs) with the algorithm
number {TBA2}.
</t>
<t>
The key size of RSA/SHA-512
keys MUST NOT be less than 1024 bits, and MUST NOT be
more than 4096 bits.
</t>
</section>
</section>
<section anchor="rrsig" title="RRSIG Resource Records">
<t>
The value of the signature field in the RRSIG RR
follows the RSASSA-PKCS1-v1_5 signature scheme, and
is calculated as follows. The values for the RDATA
fields that precede the signature data are
specified in RFC 4034 <xref target="RFC4034" />.
</t>
<t>
hash = SHA-XXX(data)
</t>
<t>
Here XXX is either 256 or 512, depending on the
algorithm used, as specified in FIPS PUB 180-3
<xref target="FIPS.180-3.2008"/>, and "data" is
the wire format data of the resource record set
that is signed, as specified in RFC 4034 <xref
target="RFC4034"/>.
</t> <t>
signature = ( 00 | 01 | FF* | 00 | prefix | hash )
** e (mod n)
</t> <t>
Here "|" is concatenation, "00", "01", "FF" and "00"
are fixed octets of corresponding hexadecimal value,
"e" is the private exponent of the signing RSA key,
and "n" is the public modulus of the signing key. The
FF octet MUST be repeated the exact number of times
so that the total length of the concatenated term in
parentheses equals the length of the modulus of the
signer's public key ("n").
</t> <t>
The "prefix" is intended to make the use of standard
cryptographic libraries easier. These specifications
are taken directly from the specifications of
RSASSA-PKCS1-v1_5 in PKCS #1 v2.1 section 8.2 <xref
target="RFC3447"/>, and EMSA-PKCS1-v1_5 encoding in
PKCS #1 v2.1 section 9.2 <xref target="RFC3447"/>. The
prefixes for the different algorithms are specified
below.
</t>
<section anchor="rrsig-sha256" title="RSA/SHA-256 RRSIG
Resource Records">
<t>
RSA/SHA-256 signatures are stored in the DNS using
RRSIG resource records (RRs) with algorithm number
{TBA1}.
</t>
<t>
The prefix is the ASN.1 DER SHA-256 algorithm
designator prefix as specified in PKCS #1 v2.1 <xref
target="RFC3447"/>:
</t>
<t>
hex 30 31 30 0d 06 09 60 86 48 01 65 03 04 02 01 05
00 04 20
</t>
</section> <section anchor="rrsig-sha512" title="RSA/SHA-512
RRSIG Resource Records">
<t>
RSA/SHA-512 signatures are stored in the DNS using
RRSIG resource records (RRs) with algorithm number
{TBA2}.
</t> <t>
The prefix is the ASN.1 DER SHA-512 algorithm
designator prefix as specified in PKCS #1 v2.1 <xref
target="RFC3447"/>:
</t> <t>
hex 30 51 30 0d 06 09 60 86 48 01 65 03 04 02 03 05
00 04 40
</t>
</section>
</section> <section anchor="deployment" title="Deployment
Considerations">
<section anchor="keysizes" title="Key Sizes">
<t>
Apart from the restrictions specified in section 2,
this document will not specify what size of keys to
use. That is an operational issue and depends largely
on the environment and intended use. A good starting
point for more information would be NIST SP 800-57
<xref target="NIST800-57"/>.
</t>
</section> <section anchor="sigsizes" title="Signature
Sizes">
<t>
In this family of signing algorithms, the size of
signatures is related to the size of the key, and not the
hashing algorithm used in the signing process. Therefore,
RRSIG resource records produced with RSA/SHA256 or
RSA/SHA512 will have the same size as those produced
with RSA/SHA1, if the keys have the same length.
</t>
</section>
</section> <section anchor="implementation"
title="Implementation Considerations">
<section title="Support for SHA-2 signatures">
<t>
DNSSEC aware implementations SHOULD be able to support
RRSIG resource records with the RSA/SHA-2 algorithms.
</t>
</section>
<section title="Support for NSEC3 Denial of Existence">
<t>
Note that these algorithms have no aliases to signal NSEC3
<xref target="RFC5155"/> denial of existence. The aliases
mechanism used in RFC 5155 was to protect implementations
predating that RFC from encountering records they could not
know about.
</t>
<section title="NSEC3 in Authoritative servers">
<t>
An authoritative server that does not implement NSEC3 MAY
still serve zones that use RSA/SHA2 with NSEC.
</t>
</section>
<section title="NSEC3 in Validators">
<t>
A DNSSEC validator that implements RSA/SHA2 MUST be able to
handle both NSEC and NSEC3 <xref target="RFC5155"/> negative
answers. If this is not the case, the validator MUST treat a
zone signed with RSA/SHA256 or RSA/SHA512 as signed with an
unknown algorithm, and thus as insecure.
</t>
</section>
</section>
</section> <section anchor="IANA" title="IANA Considerations">
<t>
This document updates the IANA registry "DNS SECURITY ALGORITHM
NUMBERS -- per <xref target="RFC4035"/> "
(http://www.iana.org/assignments/dns-sec-alg-numbers).
The following entries are added to the registry:
</t> <figure>
<artwork><![CDATA[
Zone
Value Algorithm Mnemonic Signing References
{TBA1} RSA/SHA-256 RSASHA256 y {this memo}
{TBA2} RSA/SHA-512 RSASHA512 y {this memo}
]]></artwork>
</figure>
</section> <section anchor="security" title="Security Considerations">
<section anchor="security_sha1_vs_sha2" title="SHA-1
versus SHA-2 Considerations for RRSIG Resource Records">
<t>
Users of DNSSEC are encouraged to deploy SHA-2 as
soon as software implementations allow for it.
SHA-2 is widely believed to be more resilient
to attack than SHA-1, and confidence in SHA-1's
strength is being eroded by recently-announced
attacks. Regardless of whether or not the attacks
on SHA-1 will affect DNSSEC, it is believed
(at the time of this writing) that SHA-2 is the
better choice for use in DNSSEC records.
</t> <t>
SHA-2 is considered sufficiently strong for the
immediate future, but predictions about future
development in cryptography and cryptanalysis
are beyond the scope of this document.
</t> <t>
The signature scheme RSASSA-PKCS1-v1_5 is chosen to
match the one used for RSA/SHA-1 signatures. This
should ease implementation of the new hashing
algorithms in DNSSEC software.
</t>
</section> <section anchor="downgrade_attacks"
title="Signature Type Downgrade Attacks">
<t>
Since each RRSet MUST be signed with each
algorithm present in the DNSKEY RRSet at the
zone apex (see <xref target="RFC4035"/> Section
2.2), a malicious party cannot filter out the
RSA/SHA-2 RRSIG, and force the validator to use
the RSA/SHA-1 signature if both are present in
the zone. This should provide resilience against
algorithm downgrade attacks, if the validator
supports RSA/SHA-2.
</t>
</section>
</section> <section anchor="acknowledgments"
title="Acknowledgments">
<t>
This document is a minor extension to RFC 4034
<xref target="RFC4034"/>. Also, we try to follow
the documents RFC 3110 <xref target="RFC3110"/> and
RFC 4509 <xref target="RFC4509" /> for consistency.
The authors of and contributors to these documents
are gratefully acknowledged for their hard work.
</t> <t>
The following people provided additional feedback
and text: Jaap Akkerhuis, Roy Arends, Rob Austein,
Francis Dupont, Miek Gieben, Alfred Hoenes,
Paul Hoffman, Peter Koch, Michael St. Johns,
Scott Rose and Wouter Wijngaards.
</t>
</section>
</middle> <back>
<!-- normative references -->
<references title='Normative References'>
<reference anchor="FIPS.180-3.2008">
<front>
<title>Secure Hash Standard</title>
<author>
<organization>National Institute of Standards and Technology</organization>
</author>
<date month="October" year="2008"/>
</front>
<seriesInfo name="FIPS" value="PUB 180-3"/>
</reference>
<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>
</author>
<date year='1997' month='March' />
<area>General</area>
</front>
<seriesInfo name='RFC' value='2119' />
<format type='TXT' target='ftp://ftp.isi.edu/in-notes/rfc2119.txt' />
</reference>
<reference anchor='RFC3110'>
<front>
<title>RSA/SHA-1 SIGs and RSA KEYs in the Domain Name System (DNS)</title>
<author initials='D.' surname='Eastlake' fullname='D. Eastlake'>
<organization /></author>
<date year='2001' month='May' /></front>
<seriesInfo name='RFC' value='3110' />
<format type='TXT' octets='14587' target='ftp://ftp.isi.edu/in-notes/rfc3110.txt' />
</reference>
<reference anchor='RFC4033'>
<front>
<title>DNS Security Introduction and Requirements</title>
<author initials='R.' surname='Arends' fullname='R. Arends'>
<organization /></author>
<author initials='R.' surname='Austein' fullname='R. Austein'>
<organization /></author>
<author initials='M.' surname='Larson' fullname='M. Larson'>
<organization /></author>
<author initials='D.' surname='Massey' fullname='D. Massey'>
<organization /></author>
<author initials='S.' surname='Rose' fullname='S. Rose'>
<organization /></author>
<date year='2005' month='March' />
</front>
<seriesInfo name='RFC' value='4033' />
<format type='TXT' octets='52445' target='ftp://ftp.isi.edu/in-notes/rfc4033.txt' />
</reference>
<reference anchor='RFC4034'>
<front>
<title>Resource Records for the DNS Security Extensions</title>
<author initials='R.' surname='Arends' fullname='R. Arends'>
<organization /></author>
<author initials='R.' surname='Austein' fullname='R. Austein'>
<organization /></author>
<author initials='M.' surname='Larson' fullname='M. Larson'>
<organization /></author>
<author initials='D.' surname='Massey' fullname='D. Massey'>
<organization /></author>
<author initials='S.' surname='Rose' fullname='S. Rose'>
<organization /></author>
<date year='2005' month='March' /></front>
<seriesInfo name='RFC' value='4034' />
<format type='TXT' octets='63879' target='ftp://ftp.isi.edu/in-notes/rfc4034.txt' />
</reference>
<reference anchor='RFC4035'>
<front>
<title>Protocol Modifications for the DNS Security Extensions</title>
<author initials='R.' surname='Arends' fullname='R. Arends'>
<organization /></author>
<author initials='R.' surname='Austein' fullname='R. Austein'>
<organization /></author>
<author initials='M.' surname='Larson' fullname='M. Larson'>
<organization /></author>
<author initials='D.' surname='Massey' fullname='D. Massey'>
<organization /></author>
<author initials='S.' surname='Rose' fullname='S. Rose'>
<organization /></author>
<date year='2005' month='March' /></front>
<seriesInfo name='RFC' value='4035' />
<format type='TXT' octets='130589' target='ftp://ftp.isi.edu/in-notes/rfc4035.txt' />
</reference>
</references>
<!-- informative references -->
<references title='Informative References'>
<reference anchor='NIST800-57'>
<front>
<title>Recommendations for Key Management</title>
<author initials='E.' surname='Barker' fullname='E. Barker'>
<organization/>
</author>
<author initials='W.' surname='Barker' fullname='W. Barker'>
<organization/>
</author>
<author initials='W.' surname='Burr' fullname='W. Burr'>
<organization/>
</author>
<author initials='W.' surname='Polk' fullname='W. Polk'>
<organization/>
</author>
<author initials='M.' surname='Smid' fullname='M. Smid'>
<organization/>
</author>
<date year='2007' month='March'/>
</front>
<seriesInfo name='NIST SP' value='800-57' />
</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' /></front>
<seriesInfo name='RFC' value='3447' />
<format type='TXT' octets='143173' target='ftp://ftp.isi.edu/in-notes/rfc3447.txt' />
</reference>
<reference anchor='RFC4509'>
<front>
<title> Use of SHA-256 in DNSSEC Delegation Signer (DS) Resource Records (RRs)</title>
<author initials='W.' surname='Hardaker' fullname='Wes Hardaker'>
<organization /></author>
<date year='2006' month='May' /></front>
<seriesInfo name='RFC' value='4509' />
<format type='TXT' octets='63879' target='ftp://ftp.isi.edu/in-notes/rfc4059.txt' />
</reference>
<reference anchor='RFC5155'>
<front>
<title>DNS Security (DNSSEC) Hashed Authenticated Denial of Existence</title>
<author initials='B.' surname='Laurie' fullname='B. Laurie'>
<organization />
</author>
<author initials='G' surname='Sisson' fullname='G. Sisson'>
<organization />
</author>
<author initials='R' surname='Arends' fullname='R. Arends'>
<organization />
</author>
<author initials='D' surname='Blacka' fullname='D. Blacka'>
<organization />
</author>
<date year='2008' month='March' />
</front>
<seriesInfo name='RFC' value='5155' />
<format type='TXT' target='ftp://ftp.isi.edu/in-notes/rfc5155.txt' />
</reference>
</references>
</back>
</rfc>
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