EVP_PKEY-SM2, EVP_KEYMGMT-SM2, SM2 - EVP_PKEY keytype support for the Chinese
SM2 signature and encryption algorithms
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 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).
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.
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.
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)
EVP_PKEY_CTX_new(3),
EVP_DigestSignInit(3),
EVP_DigestVerifyInit(3),
EVP_PKEY_CTX_set1_id(3),
EVP_MD_CTX_set_pkey_ctx(3)
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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>.