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 the key
ctx->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.
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.
EXAMPLES
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 = 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_ctrl(3), EVP_PKEY_CTX_new(3), EVP_PKEY_decrypt(3), EVP_PKEY_derive(3), EVP_PKEY_encrypt(3), EVP_PKEY_verify(3), EVP_PKEY_verify_recover(3)
HISTORY
EVP_PKEY_sign_init
() and
EVP_PKEY_sign
() first appeared in OpenSSL 1.0.0 and
have been available since OpenBSD 4.9.