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Improve EVP_PKEY_sign documentation

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Clarify the intended use of EVP_PKEY_sign. Make the code example compile.

Reviewed-by: Dr Stephen Henson <steve@openssl.org>
This commit is contained in:
Emilia Kasper 2014-08-22 13:16:55 +02:00
parent a520ae3628
commit d64c533a20
1 changed files with 15 additions and 5 deletions
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20
doc/crypto/EVP_PKEY_sign.pod
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@ -28,9 +28,14 @@ B<sig> and the amount of data written to B<siglen>.
=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<EVP_DigestSignInit(3)|EVP_DigestSignInit(3)> and
L<EVP_SignInit(3)|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.
operation (see L<EVP_PKEY_CTX_ctrl(3)|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.
@ -49,13 +54,17 @@ Sign data using RSA with PKCS#1 padding and SHA256 digest:
#include <openssl/rsa.h>
EVP_PKEY_CTX *ctx;
/* md is a SHA-256 digest in this example. */
unsigned char *md, *sig;
size_t mdlen, siglen;
size_t mdlen = 32, siglen;
EVP_PKEY *signing_key;
/* NB: assumes signing_key, md and mdlen are already set up
* and that signing_key is an RSA private 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);
ctx = EVP_PKEY_CTX_new(signing_key, NULL /* no engine */);
if (!ctx)
/* Error occurred */
if (EVP_PKEY_sign_init(ctx) <= 0)
@ -83,6 +92,7 @@ Sign data using RSA with PKCS#1 padding and SHA256 digest:
=head1 SEE ALSO
L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>,
L<EVP_PKEY_CTX_ctrl(3)|EVP_PKEY_CTX_ctrl(3)>,
L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>,
L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)>,
L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)>,