draft-ietf-dnsext-dnssec-rsasha256-01.txt		draft-ietf-dnsext-dnssec-rsasha256-02.txt
	DNS Extensions working group J. Jansen		DNS Extensions working group J. Jansen
	Internet-Draft NLnet Labs		Internet-Draft NLnet Labs
	Expires: July 5, 2006 January 2006		Expires: June 13, 2008 December 11, 2007
	Use of RSA/SHA-256 DNSKEY and RRSIG Resource Records in DNSSEC		Use of SHA-2 algorithms with RSA in DNSKEY and RRSIG Resource Records
	draft-ietf-dnsext-dnssec-rsasha256-01		for DNSSEC
			draft-ietf-dnsext-dnssec-rsasha256-02
	Status of this Memo		Status of this Memo
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	Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (2006).		Copyright (C) The IETF Trust (2007).
	Abstract		Abstract
	This document describes how to produce RSA/SHA-256 DNSKEY and RRSIG		This document describes how to produce RSA/SHA-256 and RSA/SHA-512
	resource records for use in the Domain Name System Security		DNSKEY and RRSIG resource records for use in the Domain Name System
	Extensions (DNSSEC, RFC4033, RFC4034, and RFC4035).		Security Extensions (DNSSEC, RFC4033, RFC4034, and RFC4035).
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. RSA/SHA-256 DNSKEY Resource Records . . . . . . . . . . . . . 3		2. DNSKEY Resource Records . . . . . . . . . . . . . . . . . . . . 3
	3. RSA/SHA-256 RRSIG Resource Records . . . . . . . . . . . . . . 3		2.1. RSA/SHA-256 DNSKEY Resource Records . . . . . . . . . . . . 3
	4. Implementation Considerations . . . . . . . . . . . . . . . . 4		2.2. RSA/SHA-512 DNSKEY Resource Records . . . . . . . . . . . . 3
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4		3. RRSIG Resource Records . . . . . . . . . . . . . . . . . . . . 4
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 4		3.1. RSA/SHA-256 RRSIG Resource Records . . . . . . . . . . . . 4
	6.1 SHA-1 versus SHA-256 Considerations for RRSIG resource		3.2. RSA/SHA-512 RRSIG Resource Records . . . . . . . . . . . . 4
	records . . . . . . . . . . . . . . . . . . . . . . . . . 4		4. Implementation Considerations . . . . . . . . . . . . . . . . . 5
	6.2 Signature Type Downgrade Attacks . . . . . . . . . . . . . 5		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
	7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5		6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5		6.1. SHA-1 versus SHA-2 Considerations for RRSIG resource
	8.1 Normative References . . . . . . . . . . . . . . . . . . . 5		records . . . . . . . . . . . . . . . . . . . . . . . . . . 5
	8.2 Informative References . . . . . . . . . . . . . . . . . . 6		6.2. Signature Type Downgrade Attacks . . . . . . . . . . . . . 6
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . 6		7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
	Intellectual Property and Copyright Statements . . . . . . . . 7		8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
			8.1. Normative References . . . . . . . . . . . . . . . . . . . 6
			8.2. Informative References . . . . . . . . . . . . . . . . . . 7
			Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7
			Intellectual Property and Copyright Statements . . . . . . . . . . 8
	1. Introduction		1. Introduction
	The Domain Name System (DNS) is the global hierarchical distributed		The Domain Name System (DNS) is the global hierarchical distributed
	database for Internet Addressing. The DNS has been extended to use		database for Internet Addressing. The DNS has been extended to use
	digital signatures and cryptographic keys for the verification of		cryptographic keys and digital signatures for the verification of the
	data. RFC4033 [1], RFC4034 [2], and RFC4035 [3] describe these DNS		integrity of its data. RFC4033 [1], RFC4034 [2], and RFC4035 [3]
	Security Extensions.		describe these DNS Security Extensions, called DNSSEC.
	RFC4034 describes how to store DNSKEY and RRSIG resource records, and		RFC4034 describes how to store DNSKEY and RRSIG resource records, and
	specifies a list of cryptographic algorithms to use. This document		specifies a list of cryptographic algorithms to use. This document
	extends that list with the algorithm RSA/SHA-256, and specifies how		extends that list with the algorithm RSA/SHA-256 and RSA/SHA-512, and
	to store RSA/SHA-256 DNSKEY data and how to produce RSA/SHA-256 RRSIG		specifies how to store DNSKEY data and how to produce RRSIG resource
	resource records.		records with these hash algorithms.
	Familiarity with the RSA [7] and SHA-256 [5] algorithms is assumed in		Familiarity with DNSSEC, RSA [7] and the SHA-2 [5] family of
	this document.		algorithms is assumed in this document.
	2. RSA/SHA-256 DNSKEY Resource Records		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.
	RSA public keys for use with RSA/SHA-256 are stored in DNSKEY		2. DNSKEY Resource Records
	resource records (RRs) with the algorithm number [TBA].
	The format of the DNSKEY RR can be found in RFC4034 [2] and RFC3110		The format of the DNSKEY RR can be found in RFC4034 [2] and RFC3110
	[6].		[6].
	3. RSA/SHA-256 RRSIG Resource Records		2.1. RSA/SHA-256 DNSKEY Resource Records
	RSA/SHA-256 signatures are stored in the DNS using RRSIG resource		RSA public keys for use with RSA/SHA-256 are stored in DNSKEY
	records (RRs) with algorithm number [TBA].		resource records (RRs) with the algorithm number [TBA].
			For use with NSEC3, the algorithm number of RSA/SHA-256 will be
			[TBA].
			2.2. RSA/SHA-512 DNSKEY Resource Records
			RSA public keys for use with RSA/SHA-512 are stored in DNSKEY
			resource records (RRs) with the algorithm number [TBA].
			For use with NSEC3, the algorithm number of RSA/SHA-512 will be
			[TBA].
			3. RRSIG Resource Records
	The value of the signature field in the RRSIG RR is calculated as		The value of the signature field in the RRSIG RR is calculated as
	follows. The values for the fields that precede the signature data		follows. The values for the fields that precede the signature data
	are specified in RFC4034 [2].		are specified in RFC4034 [2].
	hash = SHA-256(data)		hash = SHA-XXX(data)
			Where XXX is either 256 or 512, depending on the algorithm used.
	signature = ( 00 | 01 | FF* | 00 | prefix | hash ) ** e (mod n)		signature = ( 00 | 01 | FF* | 00 | prefix | hash ) ** e (mod n)
	Where SHA-256 is the message digest algorithm as specified in FIPS		Where SHA-XXX is the message digest algorithm as specified in FIPS
	180 [5], | is concatenation, 00, 01, FF and 00 are fixed octets of		180 [5], | is concatenation, 00, 01, FF and 00 are fixed octets of
	corresponding hexadecimal value, "e" is the private exponent of the		corresponding hexadecimal value, "e" is the private exponent of the
	signing RSA key, and "n" is the public modulus of the signing key.		signing RSA key, and "n" is the public modulus of the signing key.
	The FF octet MUST be repeated the maximum number of times so that the		The FF octet MUST be repeated the maximum number of times so that the
	total length of the signature equals the length of the modulus of the		total length of the signature equals the length of the modulus of the
	signer's public key ("n"). "data" is the data of the resource record		signer's public key ("n"). "data" is the data of the resource record
	set that is signed, as specified in RFC4034 [2].		set that is signed, as specified in RFC4034 [2].
			The prefix should make the use of standard cryptographic libraries
			easier. These specifications are taken directly from PKCS #1 v2.1
			section 9.2 [4]. The prefixes for the different algorithms are
			specified below.
			3.1. RSA/SHA-256 RRSIG Resource Records
			RSA/SHA-256 signatures are stored in the DNS using RRSIG resource
			records (RRs) with algorithm number [TBA].
	The prefix is the ASN.1 BER SHA-256 algorithm designator prefix as		The prefix is the ASN.1 BER SHA-256 algorithm designator prefix as
	specified in PKCS 2.1 [4]:		specified in PKCS 2.1 [4]:
	hex 30 31 30 0d 06 09 60 86 48 01 65 03 04 02 01 05 00 04 20		hex 30 31 30 0d 06 09 60 86 48 01 65 03 04 02 01 05 00 04 20
	This prefix should make the use of standard cryptographic libraries		3.2. RSA/SHA-512 RRSIG Resource Records
	easier. These specifications are taken directly from PKCS #1 v2.1
	section 9.2 [4].		RSA/SHA-512 signatures are stored in the DNS using RRSIG resource
			records (RRs) with algorithm number [TBA].
			The prefix is the ASN.1 BER SHA-512 algorithm designator prefix as
			specified in PKCS 2.1 [4]:
			hex 30 51 30 0d 06 09 60 86 48 01 65 03 04 02 03 05 00 04 40
	4. Implementation Considerations		4. Implementation Considerations
	DNSSEC aware implementations MUST be able to support RRSIG resource		DNSSEC aware implementations SHOULD be able to support RRSIG resource
	records with the RSA/SHA-256 algorithm.		records with the RSA/SHA-2 algorithms.
	If both RSA/SHA-256 and RSA/SHA-1 RRSIG resource records are		If both RSA/SHA-2 and RSA/SHA-1 RRSIG resource records are available
	available for a certain rrset, with a secure path to their keys, the		for a certain rrset, with a secure path to their keys, the validator
	validator SHOULD ignore the SHA-1 signature. If the RSA/SHA-256		SHOULD ignore the SHA-1 signature. If the RSA/SHA-2 signature does
	signature does not verify the data, and the RSA/SHA-1 does, the		not verify the data, and the RSA/SHA-1 signature does, the validator
	validator SHOULD mark the data with the security status from the RSA/		SHOULD mark the data with the security status from the RSA/SHA-2
	SHA-256 signature.		signature.
	5. IANA Considerations		5. IANA Considerations
	IANA has not yet assigned an algorithm number for RSA/SHA-256.		IANA has not yet assigned an algorithm number for RSA/SHA-256 and
			RSA/SHA-512.
	The algorithm list from RFC4034 Appendix A.1 [2] is extended with the		The algorithm list from RFC4034 Appendix A.1 [2] is extended with the
	following entry:		following entries:
	Zone		Zone
	Value Algorithm [Mnemonic] Signing References Status		Value Algorithm [Mnemonic] Signing References Status
	----- ----------- ----------- -------- ---------- ---------		----- ----------- ----------- ------- ---------- --------
	[tba] RSA/SHA-256 [RSASHA256] y [TBA] MANDATORY		[TBA] RSA/SHA-256 [RSASHA256] y [TBA] OPTIONAL
			[TBA] RSA/SHA-256-NSEC3 [RSASHA256NSEC3] y [TBA] OPTIONAL
			[TBA] RSA/SHA-512 [RSASHA512] y [TBA] OPTIONAL
			[TBA] RSA/SHA-512-NSEC3 [RSASHA512NSEC3] y [TBA] OPTIONAL
	6. Security Considerations		6. Security Considerations
	6.1 SHA-1 versus SHA-256 Considerations for RRSIG resource records		6.1. SHA-1 versus SHA-2 Considerations for RRSIG resource records
	Users of DNSSEC are encouraged to deploy SHA-256 as soon as software		Users of DNSSEC are encouraged to deploy SHA-2 as soon as software
	implementations allow for it. SHA-256 is widely believed to be more		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		resilient to attack than SHA-1, and confidence in SHA-1's strength is
	being eroded by recently-announced attacks. Regardless of whether or		being eroded by recently-announced attacks. Regardless of whether or
	not the attacks on SHA-1 will affect DNSSEC, it is believed (at the		not the attacks on SHA-1 will affect DNSSEC, it is believed (at the
	time of this writing) that SHA-256 is the better choice for use in DS		time of this writing) that SHA-2 is the better choice for use in
	records.		DNSSEC records.
	SHA-256 is considered sufficiently strong for the immediate future,		SHA-2 is considered sufficiently strong for the immediate future, but
	but predictions about future development in cryptography and		predictions about future development in cryptography and
	cryptanalysis are beyond the scope of this document.		cryptanalysis are beyond the scope of this document.
	6.2 Signature Type Downgrade Attacks		6.2. Signature Type Downgrade Attacks
	Since each RRset MUST be signed with each algorithm present in the		Since each RRset MUST be signed with each algorithm present in the
	DNSKEY RRset at the zone apex (see [3] Section 2.2), a malicious		DNSKEY RRset at the zone apex (see [3] Section 2.2), a malicious
	party cannot filter out the RSA/SHA256 RRSIG, and force the validator		party cannot filter out the RSA/SHA-2 RRSIG, and force the validator
	to use the RSA/SHA1 signature if both are present in the zone.		to use the RSA/SHA-1 signature if both are present in the zone.
	Together with the implementation considerations from Section 4 of		Together with the implementation considerations from Section 4 of
	this document, this provides resilience against algorithm downgrade		this document, this provides resilience against algorithm downgrade
	attacks, if the validator supports RSA/SHA256.		attacks, if the validator supports RSA/SHA-2.
	7. Acknowledgments		7. Acknowledgments
	This document is a minor extension to RFC4034 [2]. Also, we try to		This document is a minor extension to RFC4034 [2]. Also, we try to
	follow the documents RFC3110 [6] and draft-ietf-dnsext-ds-sha256.txt		follow the documents RFC3110 [6] and RFC4509 [8] for consistency.
	[8] for consistency. The authors of and contributors to these		The authors of and contributors to these documents are gratefully
	documents are gratefully acknowledged for their hard work.		acknowledged for their hard work.
	The following people provided additional feedback and text: Jaap		The following people provided additional feedback and text: Jaap
	Akkerhuis, Rob Austein, Miek Gieben and Wouter Wijngaards.		Akkerhuis, Rob Austein, Miek Gieben, Scott Rose and Wouter
			Wijngaards.
	8. References		8. References
	8.1 Normative References		8.1. Normative References
	[1] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,		[1] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
	"DNS Security Introduction and Requirements", RFC 4033,		"DNS Security Introduction and Requirements", RFC 4033,
	March 2005.		March 2005.
	[2] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,		[2] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
	"Resource Records for the DNS Security Extensions", RFC 4034,		"Resource Records for the DNS Security Extensions", RFC 4034,
	March 2005.		March 2005.
	[3] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,		[3] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
	skipping to change at page 6, line 5		skipping to change at page 7, line 5
	[4] Jonsson, J. and B. Kaliski, "Public-Key Cryptography Standards		[4] Jonsson, J. and B. Kaliski, "Public-Key Cryptography Standards
	(PKCS) #1: RSA Cryptography Specifications Version 2.1",		(PKCS) #1: RSA Cryptography Specifications Version 2.1",
	RFC 3447, February 2003.		RFC 3447, February 2003.
	[5] National Institute of Standards and Technology, "Secure Hash		[5] National Institute of Standards and Technology, "Secure Hash
	Standard", FIPS PUB 180-2, August 2002.		Standard", FIPS PUB 180-2, August 2002.
	[6] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain Name		[6] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain Name
	System (DNS)", RFC 3110, May 2001.		System (DNS)", RFC 3110, May 2001.
	8.2 Informative References		8.2. Informative References
	[7] Schneier, B., "Applied Cryptography Second Edition: protocols,		[7] Schneier, B., "Applied Cryptography Second Edition: protocols,
	algorithms, and source code in C", Wiley and Sons , ISBN 0-471-		algorithms, and source code in C", Wiley and Sons , ISBN 0-471-
	11709-9, 1996.		11709-9, 1996.
	[8] Hardaker, W., "Use of SHA-256 in DNSSEC Delegation Signer (DS)		[8] Hardaker, W., "Use of SHA-256 in DNSSEC Delegation Signer (DS)
	Resource Records (RRs)", Work in Progress Feb 2006.		Resource Records (RRs)", RFC 4509, May 2006.
	Author's Address		Author's Address
	Jelte Jansen		Jelte Jansen
	NLnet Labs		NLnet Labs
	Kruislaan 419		Kruislaan 419
	Amsterdam 1098VA		Amsterdam 1098VA
	NL		NL
	Email: jelte@NLnetLabs.nl		Email: jelte@NLnetLabs.nl
	URI: http://www.nlnetlabs.nl/		URI: http://www.nlnetlabs.nl/
	Intellectual Property Statement		Full Copyright Statement
			Copyright (C) The IETF Trust (2007).
			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.
			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, THE IETF TRUST 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
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	Acknowledgment		Acknowledgment
	Funding for the RFC Editor function is currently provided by the		Funding for the RFC Editor function is provided by the IETF
	Internet Society.		Administrative Support Activity (IASA).
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