ShangMi (SM) Cipher Suites for TLS 1.3Ant GroupNo. 77 Xueyuan RoadHangzhou310000China+86-571-2688-8888kaishen.yy@antfin.com
Security
TLScryptographyencryptionauthenticationnetwork securityThis document specifies how to use the ShangMi (SM) cryptographic
algorithms with Transport Layer Security (TLS) protocol version 1.3.The use of these algorithms with TLS 1.3 is not endorsed by the
IETF. The SM algorithms are becoming mandatory in China, so
this document provides a description of how to use the SM algorithms
with TLS 1.3 and specifies a profile of TLS 1.3 so that
implementers can produce interworking
implementations.Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This is a contribution to the RFC Series, independently of any
other RFC stream. The RFC Editor has chosen to publish this
document at its discretion and makes no statement about its value
for implementation or deployment. Documents approved for
publication by the RFC Editor are not candidates for any level of
Internet Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any
errata, and how to provide feedback on it may be obtained at
.
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Table of Contents
. Introduction
. The SM Algorithms
. Terminology
. Algorithm Identifiers
. Algorithm Definitions
. TLS Versions
. Authentication
. SM2 Signature Scheme
. Key Exchange
. Hello Messages
. CertificateRequest
. Certificate
. CertificateVerify
. Key Scheduling
. Cipher
. AEAD_SM4_GCM
. AEAD_SM4_CCM
. IANA Considerations
. Security Considerations
. References
. Normative References
. Informative References
. Test Vectors
. SM4-GCM Test Vectors
. SM4-CCM Test Vectors
Contributors
Author's Address
IntroductionThis document describes two new cipher suites, a signature algorithm and a
key exchange mechanism for the Transport Layer
Security (TLS) protocol version 1.3 (TLS 1.3) ().
These all utilize several ShangMi (SM) cryptographic algorithms
to fulfill the authentication and confidentiality requirements of TLS 1.3.
The new cipher suites are as follows (see also ):
CipherSuite TLS_SM4_GCM_SM3 = { 0x00, 0xC6 };
CipherSuite TLS_SM4_CCM_SM3 = { 0x00, 0xC7 };
For a more detailed
introduction to SM cryptographic algorithms, please see .
These cipher suites follow the TLS 1.3 requirements. Specifically,
all the cipher suites use SM4 in either Galois/Counter (GCM) mode
or Counter with CBC-MAC (CCM) mode to meet the needs of TLS 1.3 to have an encryption algorithm that is Authenticated Encryption with Associated Data (AEAD) capable.
The key exchange mechanism utilizes Elliptic Curve Diffie-Hellman
Ephemeral (ECDHE) over the SM2 elliptic curve, and the signature algorithm combines
the SM3 hash function and the SM2 elliptic curve signature scheme.For details about how these mechanisms negotiate shared encryption
keys, authenticate the peer(s), and protect the record structure, please see
.The cipher suites, signature algorithm, and key exchange mechanism
defined in this document are not recommended by the IETF. The SM
algorithms are becoming mandatory in China, so this document
provides a description of how to use them with TLS 1.3 and specifies
a profile of TLS 1.3 so that implementers can produce interworking
implementations.The SM AlgorithmsSeveral different SM
cryptographic algorithms are used to integrate with TLS 1.3,
including SM2 for authentication, SM4 for
encryption, and SM3 as the hash function.SM2 is a set of cryptographic algorithms based on elliptic curve cryptography, including a digital
signature, public key encryption and key exchange scheme.
In this document, only
the SM2 digital signature algorithm and basic key exchange scheme are involved, which have already been added
to ISO/IEC 14888-3:2018 (as well as to ).
SM4 is a block cipher defined in and now is being standardized
by ISO to ISO/IEC 18033-3:2010 . SM3 is a hash function that produces an output of 256 bits. SM3 has already been accepted by ISO in
ISO/IEC 10118-3:2018 and has also been described by .Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
"MAY", and "OPTIONAL" in this document are to be interpreted as
described in BCP 14
when, and only when, they appear in all capitals, as shown here.
Although this document is not an IETF Standards Track publication, it
adopts the conventions for normative language to provide clarity of
instruction to the implementer and to indicate requirement levels
for compliant TLS 1.3 implementations.Algorithm IdentifiersThe cipher suites defined here have the following identifiers:
CipherSuite TLS_SM4_GCM_SM3 = { 0x00, 0xC6 };
CipherSuite TLS_SM4_CCM_SM3 = { 0x00, 0xC7 };
To accomplish a TLS 1.3 handshake, additional objects have been introduced along with
the cipher suites as follows:
The combination of the SM2 signature algorithm and SM3 hash function used in the Signature Algorithm
extension is defined in :
SignatureScheme sm2sig_sm3 = { 0x0708 };
The SM2 elliptic curve ID used in the Supported Groups extension is defined in :
NamedGroup curveSM2 = { 41 };
Algorithm DefinitionsTLS VersionsThe new cipher suites defined in this document are only applicable to TLS 1.3.
Implementations of this document MUST NOT apply these cipher suites to any older
versions of TLS.AuthenticationSM2 Signature SchemeThe Chinese government requires the use of the SM2 signature algorithm.
This section specifies the use of the SM2 signature algorithm
as the authentication method for a TLS 1.3 handshake.The SM2 signature algorithm is defined in . The SM2 signature algorithm is
based on elliptic curves. The SM2 signature algorithm uses a fixed elliptic curve
parameter set defined in . This curve is named "curveSM2" and has been assigned the value 41, as shown in . Unlike other public key algorithms based on elliptic curve cryptography like the Elliptic Curve Digital Signature Algorithm (ECDSA), SM2 MUST NOT select other elliptic curves.
But it is acceptable to write test cases that use other elliptic curve parameter
sets for SM2; see Annex F.14 of as a reference.Implementations of the signature scheme and key exchange mechanism defined in this document MUST conform to
what requires; that is to say, the only valid elliptic curve
parameter set for the SM2 signature algorithm (a.k.a. curveSM2) is defined as follows:
curveSM2:
A prime field of 256 bits.
y2 = x3 + ax + b
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
n = FFFFFFFE FFFFFFFF FFFFFFFF FFFFFFFF
7203DF6B 21C6052B 53BBF409 39D54123
Gx = 32C4AE2C 1F198119 5F990446 6A39C994
8FE30BBF F2660BE1 715A4589 334C74C7
Gy = BC3736A2 F4F6779C 59BDCEE3 6B692153
D0A9877C C62A4740 02DF32E5 2139F0A0
The SM2 signature algorithm requests an identifier value when generating or verifying
a signature. In all uses except when a client of a server needs to verify a peer's
SM2 certificate in the Certificate message, an implementation of this document
MUST use the following ASCII string value as the SM2 identifier when doing a
TLS 1.3 key exchange:
TLSv1.3+GM+Cipher+Suite
If either a client or a server needs to verify the peer's SM2 certificate
contained in the Certificate message, then the following ASCII string value MUST be
used as the SM2 identifier according to :
1234567812345678
Expressed as octets, this is:
0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38
In practice, the SM2 identifier used in a certificate signature depends on the
certificate authority (CA) who signs that certificate. CAs may choose values other than the ones mentioned
above. Implementations of this document SHOULD confirm this information by themselves.Key ExchangeHello MessagesThe use of the algorithms defined by this document is negotiated during
the TLS handshake with information exchanged in the Hello messages.ClientHelloTo use the cipher suites defined by this document, a TLS 1.3 client includes
the new cipher suites in the "cipher_suites"
array of the ClientHello structure defined in .Other requirements of this TLS 1.3 profile on the extensions of
ClientHello message are as follows:
For the supported_groups extension, "curveSM2" MUST be included.
For the signature_algorithms extension, "sm2sig_sm3" MUST be included.
For the signature_algorithms_cert extension (if present), "sm2sig_sm3" MUST be included.
For the key_share extension, a KeyShareEntry for the "curveSM2" group MUST be included.
ServerHelloIf a TLS 1.3 server receives a ClientHello message containing the algorithms
defined in this document, it MAY choose to use them. If
so, then the server MUST put one of the new cipher suites defined in this
document into its ServerHello's "cipher_suites" array and eventually send it
to the client side.A TLS 1.3 server's choice of what cipher suite to use depends on the configuration
of the server. For instance, a TLS 1.3 server may or not be configured to include the
new cipher suites defined in this document. Typical TLS 1.3
server applications also provide a mechanism that configures the cipher suite
preference on the server side. If a server is not configured to use the cipher suites
defined in this document, it SHOULD choose another cipher suite in the list that
the TLS 1.3 client provides; otherwise, the server MUST abort the handshake with
an "illegal_parameter" alert.The following extension MUST conform to the new requirements:
For the key_share extension, a KeyShareEntry with SM2-related values MUST be added
if the server wants to conform to this profile.
CertificateRequestIf a CertificateRequest message is sent by the server to require the client
to send its certificate for authentication purposes, for conformance to this
profile, the following is REQUIRED:
The only valid signature algorithm present in "signature_algorithms" extension
MUST be "sm2sig_sm3". That is to say, if the server chooses to conform to this profile,
the signature algorithm for the client's certificate MUST use the SM2/SM3 procedure specified by this document.
CertificateWhen a server sends the Certificate message containing the server certificate
to the client side, several new rules are added that will affect the certificate
selection:
The public key in the certificate MUST be a valid SM2 public key.
The signature algorithm used by the CA to sign the current certificate MUST be
"sm2sig_sm3".
The certificate MUST be capable of signing; e.g., the digitalSignature bit
of X.509's Key Usage extension is set.
CertificateVerifyIn the CertificateVerify message, the signature algorithm MUST be "sm2sig_sm3",
indicating that the hash function MUST be SM3 and the signature algorithm MUST be
SM2.Key SchedulingAs described in , SM2 is actually a set of cryptographic
algorithms, including one key exchange protocol that defines methods such as
key derivation function, etc. This document does not define an SM2 key exchange
protocol, and an SM2 key exchange protocol SHALL NOT be used in the key exchange
steps defined in . Implementations of this document MUST always conform to
what TLS 1.3 and its successors require regarding the key derivation and
related methods.CipherThe new cipher suites introduced in this document add two new AEAD encryption
algorithms, AEAD_SM4_GCM and AEAD_SM4_CCM, which stand for SM4 cipher in Galois/Counter
mode and SM4 cipher in Counter with CBC-MAC mode, respectively.
The hash function for both cipher suites is SM3 ().This section defines the AEAD_SM4_GCM and AEAD_SM4_CCM AEAD algorithms in a
style similar to what used to define AEAD ciphers based on the AES cipher.AEAD_SM4_GCMThe AEAD_SM4_GCM authenticated encryption algorithm works as specified in ,
using SM4 as the block cipher, by providing the key, nonce, plaintext, and
associated data to that mode of operation. An authentication tag conforming to
the requirements of TLS 1.3 as specified in MUST be constructed using
the details in the TLS record header. The additional data input that forms the
authentication tag MUST be the TLS record header. The AEAD_SM4_GCM ciphertext is formed by
appending the authentication tag provided as an output to the GCM encryption
operation to the ciphertext that is output by that operation. AEAD_SM4_GCM has
four inputs: an SM4 key, an initialization vector (IV), a plaintext content, and optional
additional authenticated data (AAD). AEAD_SM4_GCM generates two outputs: a ciphertext
and message authentication code (also called an authentication tag). To have a common
set of terms for AEAD_SM4_GCM and AEAD_SM4_CCM, the AEAD_SM4_GCM IV is referred to as a
nonce in the remainder of this document. A simple test vector of AEAD_SM4_GCM and
AEAD_SM4_CCM is given in of this document.The nonce is generated by the party performing the authenticated encryption operation.
Within the scope of any authenticated encryption key, the nonce value MUST be unique.
That is, the set of nonce values used with any given key MUST NOT contain any duplicates.
Using the same nonce for two different messages encrypted with the same key
destroys the security properties of GCM mode. To generate the nonce, implementations of this document
MUST conform to TLS 1.3 (see ).The input and output lengths are as follows:
The SM4 key length is 16 octets.
The max plaintext length is 236 - 31 octets.
The max AAD length is 261 - 1 octets.
The nonce length is 12 octets.
The authentication tag length is 16 octets.
The max ciphertext length is 236 - 15 octets.
A security analysis of GCM is available in .AEAD_SM4_CCMThe AEAD_SM4_CCM authenticated encryption algorithm works as specified in
using SM4 as the block cipher. AEAD_SM4_CCM has four inputs: an SM4 key, a nonce,
a plaintext, and optional additional authenticated data (AAD). AEAD_SM4_CCM
generates two outputs: a ciphertext and a message authentication code (also called
an authentication tag). The formatting and counter generation functions are as
specified in Appendix A of , and the values of the parameters
identified in that appendix are as follows:
The nonce length n is 12.
The tag length t is 16.
The value of q is 3.
An authentication tag is also used in AEAD_SM4_CCM. The generation of the authentication
tag MUST conform to TLS 1.3 (See ).
The AEAD_SM4_CCM ciphertext is formed by appending the authentication tag provided
as an output to the CCM encryption operation to the ciphertext that is output
by that operation. The input and output lengths are as follows:
The SM4 key length is 16 octets.
The max plaintext length is 224 - 1 octets.
The max AAD length is 264 - 1 octets.
The max ciphertext length is 224 + 15 octets.
To generate the nonce, implementations of this document MUST conform to
TLS 1.3 (see ).A security analysis of CCM is available in .IANA ConsiderationsIANA has assigned the values {0x00,0xC6} and {0x00,0xC7} with the names
"TLS_SM4_GCM_SM3" and "TLS_SM4_CCM_SM3"
to the "TLS Cipher Suites" registry with this document as reference:
Value
Description
DTLS-OK
Recommended
Reference
0x00,0xC6
TLS_SM4_GCM_SM3
No
No
RFC 8998
0x00,0xC7
TLS_SM4_CCM_SM3
No
No
RFC 8998
IANA has assigned the value 0x0708 with the name "sm2sig_sm3" to the
"TLS SignatureScheme" registry:
Value
Description
Recommended
Reference
0x0708
sm2sig_sm3
No
RFC 8998
IANA has assigned the value 41 with the name "curveSM2" to the
"TLS Supported Groups" registry:
Value
Description
DTLS-OK
Recommended
Reference
41
curveSM2
No
No
RFC 8998
Security ConsiderationsAt the time of writing, there are no known weak keys for SM
cryptographic algorithms SM2, SM3 and SM4, and no security issues
have been found for these algorithms.A security analysis of GCM is available in .A security analysis of CCM is available in .ReferencesNormative ReferencesRecommendation for Block Cipher Modes of Operation: the CCM Mode for Authentication and ConfidentialityNational Institute of Standards and TechnologyRecommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMACNational Institute of Standards and TechnologyIT Security techniques -- Digital signatures with appendix -- Part 3: Discrete logarithm based mechanismsInternational Organization for StandardizationIT Security techniques -- Hash-functions -- Part 3: Dedicated hash-functionsInternational Organization for StandardizationInformation technology -- Security techniques -- Encryption algorithms -- Part 3: Block ciphersInternational Organization for StandardizationKey words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.An Interface and Algorithms for Authenticated EncryptionThis document defines algorithms for Authenticated Encryption with Associated Data (AEAD), and defines a uniform interface and a registry for such algorithms. The interface and registry can be used as an application-independent set of cryptoalgorithm suites. This approach provides advantages in efficiency and security, and promotes the reuse of crypto implementations. [STANDARDS-TRACK]Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.The Transport Layer Security (TLS) Protocol Version 1.3This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery.This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations.Informative ReferencesInformation security technology --- SM3 cryptographic hash algorithmStandardization Administration of ChinaInformation security technology -- SM4 block cipher algorithmStandardization Administration of the People's Republic of ChinaInformation security technology --- Public key cryptographic algorithm SM2 based on elliptic curves --- Part 2: Digital signature algorithmStandardization Administration of the People's Republic of ChinaInformation security technology --- Public key cryptographic algorithm SM2 based on elliptic curves --- Part 5: Parameter definitionStandardization Administration of the People's Republic of ChinaSM2 cryptography algorithm application specificationState Cryptography AdministrationOn the Security of CTR + CBC-MACThe Security and Performance of the Galois/Counter Mode of OperationTest VectorsAll values are in hexadecimal and are in network byte order (big endian).SM4-GCM Test Vectors
Initialization Vector: 00001234567800000000ABCD
Key: 0123456789ABCDEFFEDCBA9876543210
Plaintext: AAAAAAAAAAAAAAAABBBBBBBBBBBBBBBB
CCCCCCCCCCCCCCCCDDDDDDDDDDDDDDDD
EEEEEEEEEEEEEEEEFFFFFFFFFFFFFFFF
EEEEEEEEEEEEEEEEAAAAAAAAAAAAAAAA
Associated Data: FEEDFACEDEADBEEFFEEDFACEDEADBEEFABADDAD2
CipherText: 17F399F08C67D5EE19D0DC9969C4BB7D
5FD46FD3756489069157B282BB200735
D82710CA5C22F0CCFA7CBF93D496AC15
A56834CBCF98C397B4024A2691233B8D
Authentication Tag: 83DE3541E4C2B58177E065A9BF7B62EC
SM4-CCM Test Vectors
Initialization Vector: 00001234567800000000ABCD
Key: 0123456789ABCDEFFEDCBA9876543210
Plaintext: AAAAAAAAAAAAAAAABBBBBBBBBBBBBBBB
CCCCCCCCCCCCCCCCDDDDDDDDDDDDDDDD
EEEEEEEEEEEEEEEEFFFFFFFFFFFFFFFF
EEEEEEEEEEEEEEEEAAAAAAAAAAAAAAAA
Associated Data: FEEDFACEDEADBEEFFEEDFACEDEADBEEFABADDAD2
CipherText: 48AF93501FA62ADBCD414CCE6034D895
DDA1BF8F132F042098661572E7483094
FD12E518CE062C98ACEE28D95DF4416B
ED31A2F04476C18BB40C84A74B97DC5B
Authentication Tag: 16842D4FA186F56AB33256971FA110F4
ContributorsAnt Groupzhuolong.lq@antfin.comAnt Groupkepeng.lkp@antfin.comAnt Groupwilliam.zk@antfin.comAnt Grouphan.xiao@antfin.comPeking Universityguan@pku.edu.cnAuthor's AddressAnt GroupNo. 77 Xueyuan RoadHangzhou310000China+86-571-2688-8888kaishen.yy@antfin.com