1=pod 2 3=head1 NAME 4 5EVP_PKEY_sign_init, EVP_PKEY_sign - sign using a public key algorithm 6 7=head1 SYNOPSIS 8 9 #include <openssl/evp.h> 10 11 int EVP_PKEY_sign_init(EVP_PKEY_CTX *ctx); 12 int EVP_PKEY_sign(EVP_PKEY_CTX *ctx, 13 unsigned char *sig, size_t *siglen, 14 const unsigned char *tbs, size_t tbslen); 15 16=head1 DESCRIPTION 17 18The EVP_PKEY_sign_init() function initializes a public key algorithm 19context using key B<pkey> for a signing operation. 20 21The EVP_PKEY_sign() function performs a public key signing operation 22using B<ctx>. The data to be signed is specified using the B<tbs> and 23B<tbslen> parameters. If B<sig> is B<NULL> then the maximum size of the output 24buffer is written to the B<siglen> parameter. If B<sig> is not B<NULL> then 25before the call the B<siglen> parameter should contain the length of the 26B<sig> buffer, if the call is successful the signature is written to 27B<sig> and the amount of data written to B<siglen>. 28 29=head1 NOTES 30 31EVP_PKEY_sign() does not hash the data to be signed, and therefore is 32normally used to sign digests. For signing arbitrary messages, see the 33L<EVP_DigestSignInit(3)> and 34L<EVP_SignInit(3)> signing interfaces instead. 35 36After the call to EVP_PKEY_sign_init() algorithm specific control 37operations can be performed to set any appropriate parameters for the 38operation (see L<EVP_PKEY_CTX_ctrl(3)>). 39 40The function EVP_PKEY_sign() can be called more than once on the same 41context if several operations are performed using the same parameters. 42 43=head1 RETURN VALUES 44 45EVP_PKEY_sign_init() and EVP_PKEY_sign() return 1 for success and 0 46or a negative value for failure. In particular a return value of -2 47indicates the operation is not supported by the public key algorithm. 48 49=head1 EXAMPLES 50 51Sign data using RSA with PKCS#1 padding and SHA256 digest: 52 53 #include <openssl/evp.h> 54 #include <openssl/rsa.h> 55 56 EVP_PKEY_CTX *ctx; 57 /* md is a SHA-256 digest in this example. */ 58 unsigned char *md, *sig; 59 size_t mdlen = 32, siglen; 60 EVP_PKEY *signing_key; 61 62 /* 63 * NB: assumes signing_key and md are set up before the next 64 * step. signing_key must be an RSA private key and md must 65 * point to the SHA-256 digest to be signed. 66 */ 67 ctx = EVP_PKEY_CTX_new(signing_key, NULL /* no engine */); 68 if (!ctx) 69 /* Error occurred */ 70 if (EVP_PKEY_sign_init(ctx) <= 0) 71 /* Error */ 72 if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0) 73 /* Error */ 74 if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0) 75 /* Error */ 76 77 /* Determine buffer length */ 78 if (EVP_PKEY_sign(ctx, NULL, &siglen, md, mdlen) <= 0) 79 /* Error */ 80 81 sig = OPENSSL_malloc(siglen); 82 83 if (!sig) 84 /* malloc failure */ 85 86 if (EVP_PKEY_sign(ctx, sig, &siglen, md, mdlen) <= 0) 87 /* Error */ 88 89 /* Signature is siglen bytes written to buffer sig */ 90 91 92=head1 SEE ALSO 93 94L<EVP_PKEY_CTX_new(3)>, 95L<EVP_PKEY_CTX_ctrl(3)>, 96L<EVP_PKEY_encrypt(3)>, 97L<EVP_PKEY_decrypt(3)>, 98L<EVP_PKEY_verify(3)>, 99L<EVP_PKEY_verify_recover(3)>, 100L<EVP_PKEY_derive(3)> 101 102=head1 HISTORY 103 104These functions were added in OpenSSL 1.0.0. 105 106=head1 COPYRIGHT 107 108Copyright 2006-2019 The OpenSSL Project Authors. All Rights Reserved. 109 110Licensed under the OpenSSL license (the "License"). You may not use 111this file except in compliance with the License. You can obtain a copy 112in the file LICENSE in the source distribution or at 113L<https://www.openssl.org/source/license.html>. 114 115=cut 116