NAME¶
EVP_PKEY_sign_init, EVP_PKEY_sign - sign using a public key algorithm
SYNOPSIS¶
#include <openssl/evp.h>
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);
DESCRIPTION¶
The
EVP_PKEY_sign_init() function initializes a public key algorithm
context using key
pkey for a signing operation.
The
EVP_PKEY_sign() function performs a public key signing operation
using
ctx. The data to be signed is specified using the
tbs and
tbslen parameters. If
sig is
NULL then the maximum size
of the output buffer is written to the
siglen parameter. If
sig
is not
NULL then before the call the
siglen parameter should
contain the length of the
sig buffer, if the call is successful the
signature is written to
sig and the amount of data written to
siglen.
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
EVP_DigestSignInit(3) and
EVP_SignInit(3) 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
EVP_PKEY_CTX_ctrl(3)).
The function
EVP_PKEY_sign() can be called more than once on the same
context if several operations are performed using the same parameters.
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.
EXAMPLE¶
Sign data using RSA with PKCS#1 padding and SHA256 digest:
#include <openssl/evp.h>
#include <openssl/rsa.h>
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 */
SEE ALSO¶
EVP_PKEY_CTX_new(3),
EVP_PKEY_CTX_ctrl(3),
EVP_PKEY_encrypt(3),
EVP_PKEY_decrypt(3),
EVP_PKEY_verify(3),
EVP_PKEY_verify_recover(3),
EVP_PKEY_derive(3)
HISTORY¶
These functions were first added to OpenSSL 1.0.0.