EVPVerifyInit(3) OpenSSL EVPVerifyInit(3)

NAME
       EVPVerifyInit, EVPVerifyUpdate, EVPVerifyFinal - EVP signature
       verification functions

SYNOPSIS
        #include 

        int EVPVerifyInitex(EVPMDCTX *ctx, const EVPMD *type, ENGINE *impl);
        int EVPVerifyUpdate(EVPMDCTX *ctx, const void *d, unsigned int cnt);
        int EVPVerifyFinal(EVPMDCTX *ctx,unsigned char *sigbuf, unsigned int siglen,EVPPKEY *pkey);

        int EVPVerifyInit(EVPMDCTX *ctx, const EVPMD *type);

DESCRIPTION
       The EVP signature verification routines are a high level interface to
       digital signatures.

       EVPVerifyInitex() sets up verification context ccttxx to use digest ttyyppee
       from ENGINE iimmppll. ccttxx must be initialized by calling EVPMDCTXinit()
       before calling this function.

       EVPVerifyUpdate() hashes ccnntt bytes of data at dd into the verification
       context ccttxx. This function can be called several times on the same ccttxx
       to include additional data.

       EVPVerifyFinal() verifies the data in ccttxx using the public key ppkkeeyy
       and against the ssiigglleenn bytes at ssiiggbbuuff.

       EVPVerifyInit() initializes verification context ccttxx to use the
       default implementation of digest ttyyppee.

RETURN VALUES
       EVPVerifyInitex() and EVPVerifyUpdate() return 1 for success and 0
       for failure.

       EVPVerifyFinal() returns 1 for a correct signature, 0 for failure and
       -1 if some other error occurred.

       The error codes can be obtained by ERRgeterror(3).

NNOOTTEESS
       The EEVVPP 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
       EVPDigestInit(3).

       The call to EVPVerifyFinal() internally finalizes a copy of the digest
       context.  This means that calls to EVPVerifyUpdate() and
       EVPVerifyFinal() 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 EVPMDCTXcleanup() or a
       memory leak will occur.

BUGS
       Older versions of this documentation wrongly stated that calls to
       EVPVerifyUpdate() could not be made after calling EVPVerifyFinal().

SEE ALSO
       evp(3), EVPSignInit(3), EVPDigestInit(3), err(3), evp(3), hmac(3),
       md2(3), md5(3), mdc2(3), ripemd(3), sha(3), dgst(1)

HISTORY       EVPVerifyInit(), EVPVerifyUpdate() and EVPVerifyFinal() are
       available in all versions of SSLeay and OpenSSL.

       EVPVerifyInitex() was added in OpenSSL 0.9.7



0.9.7l                            2002-07-10                 EVPVerifyInit(3)