EVP_PKEY-SM2(7SSL) OpenSSL EVP_PKEY-SM2(7SSL)
NAME
EVP_PKEY-SM2, EVP_KEYMGMT-SM2, SM2 - EVP_PKEY keytype support for the
Chinese SM2 signature and encryption algorithms
DESCRIPTION
The SM2 algorithm was first defined by the Chinese national standard
GM/T 0003-2012 and was later standardized by ISO as ISO/IEC 14888. SM2
is actually an elliptic curve based algorithm. The current
implementation in OpenSSL supports both signature and encryption schemes
via the EVP interface.
When doing the SM2 signature algorithm, it requires a distinguishing
identifier to form the message prefix which is hashed before the real
message is hashed.
Common SM2 parameters
SM2 uses the parameters defined in "Common EC parameters" in
EVP_PKEY-EC(7). The following parameters are different:
"cofactor" (OSSL_PKEY_PARAM_EC_COFACTOR) <unsigned integer>
This parameter is ignored for SM2.
(OSSL_PKEY_PARAM_DEFAULT_DIGEST) <UTF8 string>
Getter that returns the default digest name. (Currently returns
"SM3" as of OpenSSL 3.0).
NOTES
SM2 signatures can be generated by using the 'DigestSign' series of
APIs, for instance, EVP_DigestSignInit(), EVP_DigestSignUpdate() and
EVP_DigestSignFinal(). Ditto for the verification process by calling
the 'DigestVerify' series of APIs. Note that the SM2 algorithm requires
the presence of the public key for signatures, as such the
OSSL_PKEY_PARAM_PUB_KEY option must be set on any key used in signature
generation.
Before computing an SM2 signature, an EVP_PKEY_CTX needs to be created,
and an SM2 ID must be set for it, like this:
EVP_PKEY_CTX_set1_id(pctx, id, id_len);
Before calling the EVP_DigestSignInit() or EVP_DigestVerifyInit()
functions, that EVP_PKEY_CTX should be assigned to the EVP_MD_CTX, like
this:
EVP_MD_CTX_set_pkey_ctx(mctx, pctx);
There is normally no need to pass a pctx parameter to
EVP_DigestSignInit() or EVP_DigestVerifyInit() in such a scenario.
SM2 can be tested with the openssl-speed(1) application since version
3.0. Currently, the only valid algorithm name is sm2.
Since version 3.0, SM2 keys can be generated and loaded only when the
domain parameters specify the SM2 elliptic curve.
EXAMPLES
This example demonstrates the calling sequence for using an EVP_PKEY to
verify a message with the SM2 signature algorithm and the SM3 hash
algorithm:
#include <openssl/evp.h>
/* obtain an EVP_PKEY using whatever methods... */
mctx = EVP_MD_CTX_new();
pctx = EVP_PKEY_CTX_new(pkey, NULL);
EVP_PKEY_CTX_set1_id(pctx, id, id_len);
EVP_MD_CTX_set_pkey_ctx(mctx, pctx);
EVP_DigestVerifyInit(mctx, NULL, EVP_sm3(), NULL, pkey);
EVP_DigestVerifyUpdate(mctx, msg, msg_len);
EVP_DigestVerifyFinal(mctx, sig, sig_len)
SEE ALSO
EVP_PKEY_CTX_new(3), EVP_DigestSignInit(3), EVP_DigestVerifyInit(3),
EVP_PKEY_CTX_set1_id(3), EVP_MD_CTX_set_pkey_ctx(3)
COPYRIGHT
Copyright 2018-2024 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>.
3.5.4 2025-09-30 EVP_PKEY-SM2(7SSL)
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