EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal - EVP signature
int EVP_VerifyInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
int EVP_VerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
int EVP_VerifyFinal(EVP_MD_CTX *ctx,unsigned char *sigbuf, unsigned int siglen,EVP_PKEY *pkey);
int EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type);
The EVP signature verification routines are a high level interface to
EVP_VerifyInit_ex() sets up verification context ctx to use digest
type from ENGINE impl. ctx must be initialized by calling
calling this function.
EVP_VerifyUpdate() hashes cnt bytes of data at d into the verification context ctx. This function can be called several times on the same ctx to include additional data.
EVP_VerifyFinal() verifies the data in ctx using the public key pkey
and against the siglen bytes at sigbuf.
EVP_VerifyInit() initializes verification context ctx to use the default implementation of digest type.
1 for success and 0 for failure.
EVP_VerifyFinal() returns 1 for a correct signature, 0 for
failure and -1 if some other error occurred.
The error codes can be obtained by ERR_get_error(3).
The EVP 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.
Due to the link between message digests and public key algorithms the
correct digest algorithm must be used with the correct public key type. A
list of algorithms and associated public key algorithms appears in
The call to
EVP_VerifyFinal() internally finalizes a copy of
the digest context. This means that calls to
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.
Older versions of this documentation wrongly stated that calls to
EVP_VerifyUpdate() could not be made after calling
Since the public key is passed in the call to
any error relating to the private key (for example an unsuitable key and
digest combination) will not be indicated until after potentially large
amounts of data have been passed through
It is not possible to change the signing parameters using these function.
The previous two bugs are fixed in the newer EVP_VerifyDigest*() function.
evp(3), hmac(3), md2(3),
md5(3), mdc2(3), ripemd(3),
EVP_VerifyFinal() are available in all versions of SSLeay and
EVP_VerifyInit_ex() was added in OpenSSL 0.9.7