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EVP_PKEY_SIGN(3) | Library Functions Manual | EVP_PKEY_SIGN(3) |
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
TheEVP_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_meth_set_sign(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.March 31, 2022 | Debian |