=pod =head1 NAME EVP_DigestVerifyInit, EVP_DigestVerifyUpdate, EVP_DigestVerifyFinal, EVP_DigestVerify - EVP signature verification functions =head1 SYNOPSIS #include int EVP_DigestVerifyInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx, const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey); int EVP_DigestVerifyUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt); int EVP_DigestVerifyFinal(EVP_MD_CTX *ctx, const unsigned char *sig, size_t siglen); int EVP_DigestVerify(EVP_MD_CTX *ctx, const unsigned char *sigret, size_t siglen, const unsigned char *tbs, size_t tbslen); =head1 DESCRIPTION The EVP signature routines are a high level interface to digital signatures. EVP_DigestVerifyInit() sets up verification context B to use digest B from ENGINE B and public key B. B must be created with EVP_MD_CTX_new() before calling this function. If B is not NULL the EVP_PKEY_CTX of the verification operation will be written to B<*pctx>: this can be used to set alternative verification options. EVP_DigestVerifyUpdate() hashes B bytes of data at B into the verification context B. This function can be called several times on the same B to include additional data. This function is currently implemented using a macro. EVP_DigestVerifyFinal() verifies the data in B against the signature in B of length B. EVP_DogestVerify() verifies B bytes at B against the signature in B of length B. =head1 RETURN VALUES EVP_DigestVerifyInit() and EVP_DigestVerifyUpdate() return 1 for success and 0 for failure. EVP_DigestVerifyFinal() and EVP_DigestVerify() return 1 for success; any other value indicates failure. A return value of zero indicates that the signature did not verify successfully (that is, B did not match the original data or the signature had an invalid form), while other values indicate a more serious error (and sometimes also indicate an invalid signature form). The error codes can be obtained from L. =head1 NOTES The B interface to digital signatures should almost always be used in preference to the low level interfaces. This is because the code then becomes transparent to the algorithm used and much more flexible. EVP_DigesVerify() is a one shot operation which verifies a single block of data in one function. For algorithms that support streaming it is equivalent to calling EVP_DigestVerifyUpdate() and EVP_DigestVerifyFinal(). For algorithms which do not support streaming (e.g. PureEdDSA) it is the only way to verify data. In previous versions of OpenSSL there was a link between message digest types and public key algorithms. This meant that "clone" digests such as EVP_dss1() needed to be used to sign using SHA1 and DSA. This is no longer necessary and the use of clone digest is now discouraged. For some key types and parameters the random number generator must be seeded or the operation will fail. The call to EVP_DigestVerifyFinal() internally finalizes a copy of the digest context. This means that EVP_VerifyUpdate() and EVP_VerifyFinal() can be called later to digest and verify additional data. Since only a copy of the digest context is ever finalized the context must be cleaned up after use by calling EVP_MD_CTX_cleanup() or a memory leak will occur. =head1 SEE ALSO L, L, L, L, L, L, L, L, L, L =head1 HISTORY EVP_DigestVerifyInit(), EVP_DigestVerifyUpdate() and EVP_DigestVerifyFinal() were first added to OpenSSL 1.0.0. =head1 COPYRIGHT Copyright 2006-2017 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 L. =cut