SM2 - Chinese SM2 signature and encryption algorithm support
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.
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.
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)
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 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>.