NAME    [Toc]    [Back]

       EVP_VerifyInit,  EVP_VerifyUpdate,  EVP_VerifyFinal  - EVP
       signature verification functions

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.

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

       The EVP_VerifyUpdate() function 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.

       The  EVP_VerifyFinal()  function  verifies the data in ctx
       using the public key pkey and against the siglen bytes  at
       sigbuf.   After  calling the EVP_VerifyFinal() function no
       additional calls to the EVP_VerifyUpdate() function can be
       made,  but  the EVP_VerifyInit() function can be called to
       initialize a new verification operation.

NOTES    [Toc]    [Back]

       The EVP interface to digital signatures should 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).

RESTRICTIONS    [Toc]    [Back]

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

RETURN VALUES    [Toc]    [Back]

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

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

       The error codes can be obtained by using  ERR_get_error().

HISTORY    [Toc]    [Back]

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

SEE ALSO    [Toc]    [Back]

       Commands: dgst(1)

       Functions:   evp(3),  EVP_SignInit(3),  EVP_DigestInit(3),
       err(3),  evp(3),   hmac(3),   md2(3),   md5(3),   mdc2(3),
       ripemd(3), sha(3)



                                                EVP_VerifyInit(3)