NAME
EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal — EVP signature verification functions
Synopsis
#include <openssl/evp.h>
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);
DESCRIPTION
The EVP signature verification routines are a high level interface
to digital signatures.
EVP_VerifyInit_ex() sets up verification context ctx to
use digest type from ENGINE impl. ctx must
be initialized by calling EVP_MD_CTX_init() before 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.
RETURN VALUES
EVP_VerifyInit_ex() and EVP_VerifyUpdate() return 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).
NOTES
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 EVP_DigestInit(3).
The call to EVP_VerifyFinal() internally finalizes a copy
of the digest context. This means that calls to 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.
Restrictions
Older versions of this documentation wrongly stated that calls
to EVP_VerifyUpdate() could not be made after calling EVP_VerifyFinal().
SEE ALSO
evp(3), EVP_SignInit(3), EVP_DigestInit(3), err(3), evp(3), hmac(3), md2(3), md5(3), mdc2(3), ripemd(3), sha(3), dgst(1)
HISTORY
EVP_VerifyInit(), EVP_VerifyUpdate() and EVP_VerifyFinal()
are available in all versions of SSLeay and OpenSSL.
EVP_VerifyInit_ex() was added in OpenSSL 0.9.7
