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EVP_SignInit(3)
NAME
  EVP_SignInit, EVP_SignUpdate, EVP_SignFinal - EVP signing functions

SYNOPSIS
  #include <openssl/evp.h>

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

  void 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
  );

  int EVP_PKEY_size(
	  EVP_PKEY *pkey );

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

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

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

  The EVP_SignFinal() function signs the data in ctx using the private key
  pkey and places the signature in sig. If the s parameter is not NULL then
  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.  After calling EVP_SignFinal(), no additional calls to
  EVP_SignUpdate() can be made, but the EVP_SignInit() function can be called
  to initialize a new signature operation.

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

NOTES
  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).

  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.

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

RETURN VALUES
  The EVP_SignInit() and EVP_SignUpdate() functions do not return values.

  The EVP_SignFinal() function returns 1 for success and 0 for failure.

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

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

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

SEE ALSO
  Commands: dgst(1)

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

Index for Section 3

Alphabetical listing for E

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