EVP_VerifyInit(3)

     EVP_VerifyInit(3)      0.9.6h (2002-07-10)      EVP_VerifyInit(3)

     NAME
          EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal - EVP
          signature verification functions

     SYNOPSIS
           #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
          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_VerifyUpdate() can be made, but EVP_VerifyInit() can be
          called to initialize a new verification operation.

     RETURN VALUES
          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
          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
          Several of the functions do not return values: maybe they

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     EVP_VerifyInit(3)      0.9.6h (2002-07-10)      EVP_VerifyInit(3)

          should. Although the internal digest operations will never
          fail some future hardware based operations might.

     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.

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