| Internet-Draft | SM2 Digital Signature Algorithm for DNSS | November 2023 |
| Zhang, et al. | Expires 12 May 2024 | [Page] |
This document describes how to specify SM2 Digital Signature Algorithm keys and signatures in DNS Security (DNSSEC). It lists the curve and uses SM3 as hash algorithm for signatures.¶
This draft is an independent submission to the RFC series, and does not have consensus of the IETF community.¶
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Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶
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This Internet-Draft will expire on 4 May 2024.¶
Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
DNSSEC is broadly defined in RFCs 4033, 4034, and 4035 ([RFC4033], [RFC4034], and [RFC4035]). It uses cryptographic keys and digital signatures to provide authentication of DNS data. Currently, there are several signature algorithms, such as RSA with SHA-256 defined in RFC 5702 ([RFC5702]), and ECDSA with curve P-256 and SHA-256 defined in RFC 6605 ([RFC6605]), etc.¶
This document defines the DNSKEY and RRSIG resource records (RRs) of a new signing algorithms: SM2 uses elliptic curves over 256-bit prime fields with SM3 hash algorithm. (A description of SM2 and SM3 can be found in GB/T 32918.2-2016 [GBT-32918.2-2016] or ISO/IEC14888-3:2018 [ISO-IEC14888-3_2018], and GB/T 32905-2016 [GBT-32905-2016] or ISO/IEC10118-3:2018 [ISO-IEC10118-3_2018].) This document also defines the DS RR for the SM3 one-way hash algorithm. In the signing algorithm defined in this document, the size of the key for the elliptic curve is matched with the size of the output of the hash algorithm. Both are 256 bits.¶
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 [RFC2119].¶
SM3 is included in ISO/IEC 10118-3:2018 and is similar to SHA-256 in many ways. The implementation of SM3 in DNSSEC follows the implementation of SHA-256 as specified in RFC 4509[RFC4509] except that the underlying algorithm is SM3 with digest type code [TBD1].¶
Verifying SM2 signatures requires agreement between the signer and the verifier of the parameters used. SM2 digital signature algorithm has been added to ISO/IEC 14888-3:2018. And the parameters of the curve used in this document are as follows:¶
p = FFFFFFFE FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF 00000000 FFFFFFFF FFFFFFFF a = FFFFFFFE FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF 00000000 FFFFFFFF FFFFFFFC b = 28E9FA9E 9D9F5E34 4D5A9E4B CF6509A7 F39789F5 15AB8F92 DDBCBD41 4D940E93 xG = 32C4AE2C 1F198119 5F990446 6A39C994 8FE30BBF F2660BE1 715A4589 334C74C7 yG = BC3736A2 F4F6779C 59BDCEE3 6B692153 D0A9877C C62A4740 02DF32E5 2139F0A0 n = FFFFFFFE FFFFFFFF FFFFFFFF FFFFFFFF 7203DF6B 21C6052B 53BBF409 39D54123¶
SM2 public keys consist of a single value, called "P". In DNSSEC keys, P is a string of 32 octets that represents the uncompressed form of a curve point, "x | y".¶
The SM2 signature is the combination of two non-negative integers, called "r" and "s". The two integers, each of which is formatted as a simple octet string, are combined into a single longer octet string for DNSSEC as the concatenation "r | s". (Conversion of the integers to bit strings is the same as ECDSA signature.) Each integer MUST be encoded as 32 octets.¶
Although SM2 uses elliptic curves, the process of digest and signature generation is different from ECDSA. Process details are described in section 6 "Digital signature generation algorithm and its process" in [GBT-32918.2-2016].¶
The algorithm number associated with the DNSKEY and RRSIG resource records is [TBD2], which is described in the IANA Considerations section.¶
Conformant implementations that create records to be put into the DNS MAY implement signing and verification for the above algorithm. Conformant DNSSEC verifiers MAY implement verification for the above algorithm.¶
This document does not define algorithm aliases mentioned in RFC 5155 [RFC5155].¶
A DNSSEC validator that implements the signing algorithms defined in this document MUST be able to validate negative answers in the form of both NSEC and NSEC3 with hash algorithm 1, as defined in RFC 5155. An authoritative server that does not implement NSEC3 MAY still serve zones that use the signing algorithms defined in this document with NSEC denial of existence.¶
The following is an example of SM2 keys and signatures in DNS zone file format.¶
Private-key-format: v1.3 Algorithm: [TBD2] (SM2SM3) PrivateKey: V24tjJgXxp2ykscKRZdT+iuR5J1xRQN+FKoQACmo9fA=¶
example.net. 3600 IN DNSKEY 257 3 TBD2 (
jZbZMBImG9dtGWSVEwnv2l32OVKcX7MMJv+83/+A41ia
ZuO0ajXMcuyJbTr8Ud+kae6UlfqrnsG6tgADIPHxXA== )
example.net. 3600 IN DS 27215 TBD2 TBD1 (
86671f82dd872e4ee73647a95dff7fd0af599ff8a43f
fa26c9a2593091653c0e )
www.example.net. 3600 IN A 192.0.2.1
www.example.net. 3600 IN RRSIG A TBD2 6 3600 (
20220428075649 20220331075649 27215 example.net.
tz295lkfu2InRnLdLhKWDm354I6ZGSmYeOSDswKiQMU7
/Va0QrH7bD7ZnHB4wWsEjfy1XscwM4P86sVxkMJE7w== )
¶
This document will update the IANA registry for digest types in DS records, currently called "Delegation Signer (DS) Resource Record (RR) Type Digest Algorithms".¶
Value TBD1
Digest Type SM3
Status OPTIONAL
¶
This document will update the IANA registry "Domain Name System Security (DNSSEC) Algorithm Numbers".¶
Number TBD2
Description SM2 signing algorithm with SM3 hashing algorithm
Mnemonic SM2SM3
Zone Signing Y
Trans. Sec. *
Reference This document
¶
* There has been no determination of standardization of the use of this algorithm with Transaction Security.¶
The security strength of SM2 is considered to be equivalent to half the size of the key, which is 128 bits.¶
For another thing, the security of ECC-based algorithms is influenced by the curve it uses.¶
Thus it's recommended that the DNS server implementations use popular cryptography library which support SM2 and SM3 algorithms, such as OpenSSL. Thus it's convenient to use a different curve if SM2 is compromised.¶
The security considerations listed in RFC 4509 apply here as well.¶
This is a zone showing its RRSIG RRs generated with SM3 hash algorithm and SM2 signature algorithm.¶
example. 3600 IN SOA ns1.example. root.example. (
1 ; serial
3600 ; refresh (1 hour)
300 ; retry (5 minutes)
3600000 ; expire (5 weeks 6 days 16 hours)
3600 ; minimum (1 hour)
)
RRSIG SOA TBD2 1 3600 (
20230901000000 20220901000000 65042 example.
vXGQ/M+QJbEzdF9MW8rqJVN+QC5LdpK7k7vt
nupu/SrZhiKDGcXpORMpprlljlQ6w4YqytdA
ZHfbu25HfIyEgw== )
NS ns1.example.
NS ns2.example.
RRSIG NS TBD2 1 3600 (
20230901000000 20220901000000 65042 example.
xXR6eAWSdv9KpEtX/GccI0AFafmUoARf9Q1i
CgtoJKjFCQySqBLVxlgiQQaTpZqY8taepygv
8g5o5mHsfmyPiw== )
DNSKEY 256 3 TBD2 (
7EQ32PTAp+1ac6R9Ze2nfB8pPc2OJqkHSjug
ALr4SuD9awuQxhfw7wMpiXv7JK4/VwwTrCxJ
wu+qUuDsgoBK4w==
) ; ZSK; alg = SM2SM3 ; key id = 65042
DNSKEY 257 3 TBD2 (
jZbZMBImG9dtGWSVEwnv2l32OVKcX7MMJv+8
3/+A41iaZuO0ajXMcuyJbTr8Ud+kae6Ulfqr
nsG6tgADIPHxXA==
) ; KSK; alg = SM2SM3 ; key id = 27215
RRSIG DNSKEY TBD2 1 3600 (
20230901000000 20220901000000 65042 example.
lF2eq49e62Nn4aT5x8ZI6PdRSTPHPDixZdyl
lM6GWu4lkRWkpTgWLE4lQK/+qHdNS4DdTd36
Jsuu0FSO5k48Qg== )
RRSIG DNSKEY TBD2 1 3600 (
20230901000000 20220901000000 27215 example.
+MDF1bnH/8zCeOwJQbWSfwb6OCB8fp16rxog
S9+PbxHEcKNTOUX3hPxdM8NblDgY19c+KDmr
xei2D84M2B50cQ== )
0 NSEC3PARAM 1 0 10 AABBCCDD
0 RRSIG NSEC3PARAM TBD2 1 0 (
20230901000000 20220901000000 65042 example.
aqntwEYEJzkVb8SNuJLwdx7f+vivv5IUIeAj
6/TGt2/bewiM/Hp9fqOysEcjgWZ7lZbqJsR5
HtKlddixnjmOFQ== )
ns2.example. A 192.0.2.2
RRSIG A TBD2 2 3600 (
20230901000000 20220901000000 65042 example.
xqot4urj885t1SDnAZnozl4s3t/El1HZVLwb
0N2Bb6IdEBtH/SNJdN1Zz/xBysCGkRwoMq2I
Uk+v3Yl6Uo8Eiw== )
ns1.example. A 192.0.2.1
RRSIG A TBD2 2 3600 (
20230901000000 20220901000000 65042 example.
5ZNwC4No82PeHZd5PgdGmBsvRxjBe3FlnA4S
g8/tDZlHM7QSbDDN17r8+qHq+AeXKy8cSF3n
U+byf9VjzV9IKA== )
www.example. A 192.0.2.3
RRSIG A TBD2 2 3600 (
20230901000000 20220901000000 65042 example.
vNTwnIQzImSG6b6F0dNhNz+mt8oSRITzfiNh
mzdvI0w1eHxTetA/3Tu3HLoDYDw+D5uGcoVZ
NlvZpyrIU1BIAA== )
S0OCR8EH8COF31Q1TO66KIDIT4A4RV8R.example. NSEC3 1 1 10 AABBCCDD (
62KP1QB93KRGR6LM7SEVPJVNG90BLUE8
A RRSIG )
RRSIG NSEC3 TBD2 2 3600 (
20230901000000 20220901000000 65042 example.
ai3O/vkgVX6DRJFjfwWJI71QNXucCaTpWBAQ
JyedgjRGC/XgX1WF60SglDzWmlHdyACPHV4S
1dBE344tnNgAtA== )
GTGVQIILTSSJ8FFO9J6DC8PRTFAEA8G2.example. NSEC3 1 1 10 AABBCCDD (
NIU1DMQS67H1PIN9JIMC33JCMO8MU99T
A RRSIG )
RRSIG NSEC3 TBD2 2 3600 (
20230901000000 20220901000000 65042 example.
3BUwHiacqHADK7Y31kFa4JnGOrURCXlZNmZq
B163jles9HCQHIDR60DFZdZhx1sVBsd8Rl+L
dUcia3aUgNqwlA== )
NIU1DMQS67H1PIN9JIMC33JCMO8MU99T.example. NSEC3 1 1 10 AABBCCDD (
OHVFQ9KQA23B5PM64EST8LNRQRLQ624H
A RRSIG )
RRSIG NSEC3 TBD2 2 3600 (
20230901000000 20220901000000 65042 example.
ctAutz6smtvUeeCyZPel3BTYJzkJcYGXEDRH
hosBrWRiipM/C94nZxFpYioK+mq5tw9yebwH
83Vq94AChHbabg== )
test.example. A 192.0.2.4
RRSIG A TBD2 2 3600 (
20230901000000 20220901000000 65042 example.
H9+NQdd9o4NTj8siRO8c5IrjJ/6BuNaZdgeh
AbcwTcxBvhE7D4XeHH9zUcZ0gVuhdR8WoA8H
FVbCrekKGgW7Gw== )
OHVFQ9KQA23B5PM64EST8LNRQRLQ624H.example. NSEC3 1 1 10 AABBCCDD (
S0OCR8EH8COF31Q1TO66KIDIT4A4RV8R
A RRSIG )
RRSIG NSEC3 TBD2 2 3600 (
20230901000000 20220901000000 65042 example.
eygDRIjsL+OXE4leoBuZOFptq+FMkWGfXA19
ojaJlnRfeLXEHKBrCFMEe+8l3qlTkGFsBo3N
E3tQU4uSMafViA== )
62KP1QB93KRGR6LM7SEVPJVNG90BLUE8.example. NSEC3 1 1 10 AABBCCDD (
GTGVQIILTSSJ8FFO9J6DC8PRTFAEA8G2
NS SOA RRSIG DNSKEY NSEC3PARAM )
RRSIG NSEC3 TBD2 2 3600 (
20230901000000 20220901000000 65042 example.
FOWLegTgFkFY9vCOo4kHwjEvZ+IL1NMl4s9V
hVyPOwokd5uOLKeXTP19HIeEtW73WcJ9XNe/
ie/knp7Edo/hxw== )
¶