Manual Pages for UNIX Operating System command usage for man EVP_SignFinal

OpenSSL                                    EVP_SignInit(3openssl)



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     EVP_SignInit, EVP_SignUpdate, EVP_SignFinal - EVP signing
     functions

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      #include 

      int EVP_SignInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
      int EVP_SignUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
      int EVP_SignFinal(EVP_MD_CTX *ctx,unsigned char *sig,unsigned int *s, EVP_PKEY *pkey);

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

      int EVP_PKEY_size(EVP_PKEY *pkey);


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

     EVP_SignInit_ex() sets up signing context ccccttttxxxx to use digest
     ttttyyyyppppeeee from ENGINE iiiimmmmppppllll. ccccttttxxxx must be initialized with
     EVP_MD_CTX_init() before calling this function.

     EVP_SignUpdate() hashes ccccnnnntttt bytes of data at dddd into the
     signature context ccccttttxxxx. This function can be called several
     times on the same ccccttttxxxx to include additional data.

     EVP_SignFinal() signs the data in ccccttttxxxx using the private key
     ppppkkkkeeeeyyyy and places the signature in ssssiiiigggg. The number of bytes of
     data written (i.e. the length of the signature) will be
     written to the integer at ssss, at most EVP_PKEY_size(pkey)
     bytes will be written.

     EVP_SignInit() initializes a signing context ccccttttxxxx to use the
     default implementation of digest ttttyyyyppppeeee.

     EVP_PKEY_size() returns the maximum size of a signature in
     bytes. The actual signature returned by EVP_SignFinal() may
     be smaller.

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     EVP_SignInit_ex(), EVP_SignUpdate() and EVP_SignFinal()
     return 1 for success and 0 for failure.

     EVP_PKEY_size() returns the maximum size of a signature in
     bytes.

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

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     The EEEEVVVVPPPP interface to digital signatures should almost always



22/Mar/2005            Last change: 0.9.8o                      1






OpenSSL                                    EVP_SignInit(3openssl)



     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).

     When signing with DSA private keys the random number
     generator must be seeded or the operation will fail. The
     random number generator does not need to be seeded for RSA
     signatures.

     The call to EVP_SignFinal() internally finalizes a copy of
     the digest context.  This means that calls to
     EVP_SignUpdate() and EVP_SignFinal() can be called later to
     digest and sign 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.

BBBBUUUUGGGGSSSS
     Older versions of this documentation wrongly stated that
     calls to EVP_SignUpdate() could not be made after calling
     EVP_SignFinal().

SSSSEEEEEEEE AAAALLLLSSSSOOOO
     EVP_VerifyInit(3), EVP_DigestInit(3), err(3), evp(3),
     hmac(3), md2(3), md5(3), mdc2(3), ripemd(3), sha(3), dgst(1)

HHHHIIIISSSSTTTTOOOORRRRYYYY
     EVP_SignInit(), EVP_SignUpdate() and EVP_SignFinal() are
     available in all versions of SSLeay and OpenSSL.

     EVP_SignInit_ex() was added in OpenSSL 0.9.7.

















22/Mar/2005            Last change: 0.9.8o                      2