/usr/man/cat.3/EVP_VerifyInit.3

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 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

     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 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).

1.0.2t               Last change: 2019-09-10                    1

EVP_VerifyInit(3)            OpenSSL            EVP_VerifyInit(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

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

     Since the public key is passed in the call to
     EVP_SignFinal() any error relating to the private key (for
     example an unsuitable key and digest combination) will not
     be indicated until after potentially large amounts of data
     have been passed through EVP_SignUpdate().

     It is not possible to change the signing parameters using
     these function.

     The previous two bugs are fixed in the newer
     EVP_VerifyDigest*() function.

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.

     EVP_VerifyInit_ex() was added in OpenSSL 0.9.7

1.0.2t               Last change: 2019-09-10                    2

See also EVP_VerifyFinal(3)
See also EVP_VerifyUpdate(3)