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 pre-allocated
       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.

EXAMPLE

       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 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>.