EVP_VerifyInit(3)           OpenSSL           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 initial-
       ized 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 addi-
       tional 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 inter-
       faces. 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 final-
       ized 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_VerifyFi-
       nal() are available in all versions of SSLeay and
       OpenSSL.

       EVP_VerifyInit_ex() was added in OpenSSL 0.9.7



0.9.7c                     2002-07-10         EVP_VerifyInit(3)
