NAME    [Toc]    [Back]

       EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal - EVP
       signature verification functions

LIBRARY    [Toc]    [Back]

       libcrypto, -lcrypto

SYNOPSIS    [Toc]    [Back]

        #include <openssl/evp.h>

        void EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type);
        void 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);

DESCRIPTION    [Toc]    [Back]

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

       EVP_VerifyInit() initializes a verification context ctx to
       using digest type: this will typically be supplied by a
       function such as EVP_sha1().

       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. After
       calling EVP_VerifyFinal() no additional calls to EVP_Veri-
       fyUpdate() can be made, but EVP_VerifyInit() can be called
       to initialize a new verification operation.

RETURN VALUES    [Toc]    [Back]

       EVP_VerifyInit() and EVP_VerifyUpdate() do not return values.


       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).

BUGS    [Toc]    [Back]

       Several of the functions do not return values: maybe they
       should. Although the internal digest operations will never
       fail some future hardware based operations might.

SEE ALSO    [Toc]    [Back]

       openssl_evp(3), EVP_SignInit(3), EVP_DigestInit(3),
       openssl_err(3), openssl_evp(3), openssl_hmac(3), md2(3),
       openssl_md5(3), openssl_mdc2(3), openssl_ripemd(3),
       openssl_sha(3), openssl_dgst(1)

HISTORY    [Toc]    [Back]

       EVP_VerifyInit(), EVP_VerifyUpdate() and EVP_VerifyFinal()
       are available in all versions of SSLeay and OpenSSL.



2002-07-31                    0.9.6g            EVP_VerifyInit(3)