evp_verifyinit(3)
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.
BUGS
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