=pod
=head1 NAME
EVP_PKEY_sign_init, EVP_PKEY_sign - sign using a public key algorithm
=head1 SYNOPSIS
#include
int EVP_PKEY_sign_init(EVP_PKEY_CTX *ctx);
int EVP_PKEY_sign(EVP_PKEY_CTX *ctx,
unsigned char *sig, size_t *siglen,
const unsigned char *tbs, size_t tbslen);
=head1 DESCRIPTION
The EVP_PKEY_sign_init() function initializes a public key algorithm
context using key B for a signing operation.
The EVP_PKEY_sign() function performs a public key signing operation
using B. The data to be signed is specified using the B and
B parameters. If B is B then the maximum size of the output
buffer is written to the B parameter. If B is not B then
before the call the B parameter should contain the length of the
B buffer, if the call is successful the signature is written to
B and the amount of data written to B.
=head1 NOTES
EVP_PKEY_sign() does not hash the data to be signed, and therefore is
normally used to sign digests. For signing arbitrary messages, see the
L and
L signing interfaces instead.
After the call to EVP_PKEY_sign_init() algorithm specific control
operations can be performed to set any appropriate parameters for the
operation (see L).
The function EVP_PKEY_sign() can be called more than once on the same
context if several operations are performed using the same parameters.
=head1 RETURN VALUES
EVP_PKEY_sign_init() and EVP_PKEY_sign() return 1 for success and 0
or a negative value for failure. In particular a return value of -2
indicates the operation is not supported by the public key algorithm.
=head1 EXAMPLE
Sign data using RSA with PKCS#1 padding and SHA256 digest:
#include
#include
EVP_PKEY_CTX *ctx;
/* md is a SHA-256 digest in this example. */
unsigned char *md, *sig;
size_t mdlen = 32, siglen;
EVP_PKEY *signing_key;
/*
* NB: assumes signing_key and md are set up before the next
* step. signing_key must be an RSA private key and md must
* point to the SHA-256 digest to be signed.
*/
ctx = EVP_PKEY_CTX_new(signing_key, NULL /* no engine */);
if (!ctx)
/* Error occurred */
if (EVP_PKEY_sign_init(ctx) <= 0)
/* Error */
if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0)
/* Error */
if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0)
/* Error */
/* Determine buffer length */
if (EVP_PKEY_sign(ctx, NULL, &siglen, md, mdlen) <= 0)
/* Error */
sig = OPENSSL_malloc(siglen);
if (!sig)
/* malloc failure */
if (EVP_PKEY_sign(ctx, sig, &siglen, md, mdlen) <= 0)
/* Error */
/* Signature is siglen bytes written to buffer sig */
=head1 SEE ALSO
L,
L,
L,
L,
L,
L,
L
=head1 HISTORY
These functions were first added to OpenSSL 1.0.0.
=head1 COPYRIGHT
Copyright 2006-2016 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
L.
=cut