NAME    [Toc]    [Back]

       EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal - EVP
       signature verification functions

SYNOPSIS    [Toc]    [Back]

        #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    [Toc]    [Back]

       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    [Toc]    [Back]

       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    [Toc]    [Back]

       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    [Toc]    [Back]

       Older versions of this documentation wrongly stated that
       calls to EVP_VerifyUpdate() could not be made after calling
 EVP_VerifyFinal().

SEE ALSO    [Toc]    [Back]

       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    [Toc]    [Back]

       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


OpenBSD 3.6                 2002-09-10                          2