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SM2(7)                              OpenSSL                             SM2(7)


NAME

       SM2 - Chinese SM2 signature and encryption algorithm support


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.


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.

       There are several special steps that need to be done before computing
       an SM2 signature.

       The EVP_PKEY structure will default to using ECDSA for signatures when
       it is created. It should be set to EVP_PKEY_SM2 by calling:

        EVP_PKEY_set_alias_type(pkey, EVP_PKEY_SM2);

       Then an ID should be set by calling:

        EVP_PKEY_CTX_set1_id(pctx, id, id_len);

       When calling the EVP_DigestSignInit() or EVP_DigestVerifyInit()
       functions, a preallocated EVP_PKEY_CTX should be assigned to the
       EVP_MD_CTX. This is done by calling:

        EVP_MD_CTX_set_pkey_ctx(mctx, pctx);

       And normally there is no need to pass a pctx parameter to
       EVP_DigestSignInit() or EVP_DigestVerifyInit() in such a scenario.


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... */
        EVP_PKEY_set_alias_type(pkey, EVP_PKEY_SM2);
        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_PKEY_set_alias_type(3), EVP_DigestSignInit(3),
       EVP_DigestVerifyInit(3), EVP_PKEY_CTX_set1_id(3),
       EVP_MD_CTX_set_pkey_ctx(3)


COPYRIGHT

       Copyright 2018-2020 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (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>.

1.1.1v                            2023-08-01                            SM2(7)

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