MirOS Manual: EVP_PKEY_size(3), EVP_SignFinal(3), EVP_SignInit(3), EVP_SignUpdate(3)


EVP_SIGNINIT(3)              OpenSSL              EVP_SIGNINIT(3)

NAME

     EVP_SignInit, EVP_SignUpdate, EVP_SignFinal - EVP signing
     functions

SYNOPSIS

      #include <openssl/evp.h>

      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);

DESCRIPTION

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

     EVP_SignInit_ex() sets up signing context ctx to use digest
     type from ENGINE impl. ctx must be initialized with
     EVP_MD_CTX_init() before calling this function.

     EVP_SignUpdate() hashes cnt bytes of data at d into the sig-
     nature context ctx. This function can be called several
     times on the same ctx to include additional data.

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

     EVP_SignInit() initializes a signing context ctx to use the
     default implementation of digest type.

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

RETURN VALUES

     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).

NOTES

     The EVP interface to digital signatures should almost always
     be used in preference to the low level interfaces. This is

MirOS BSD #10-current      2016-10-06                           1

EVP_SIGNINIT(3)              OpenSSL              EVP_SIGNINIT(3)

     because the code then becomes transparent to the algorithm
     used and much more flexible.

     Due to the link between message digests and public key algo-
     rithms 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 genera-
     tor must be seeded or the operation will fail. The random
     number generator does not need to be seeded for RSA signa-
     tures.

     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.

BUGS

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

SEE ALSO

     EVP_VerifyInit(3), EVP_DigestInit(3), ERR_get_error(3),
     evp(3), HMAC(3), MD2(3), MD5(3), RIPEMD(3), SHA1(3), dig-
     est(1)

HISTORY

     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.

MirOS BSD #10-current      2016-10-06                           2

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