xref: /openssl/doc/man3/RSA_private_encrypt.pod (revision 3dbf8243)
1=pod
2
3=head1 NAME
4
5RSA_private_encrypt, RSA_public_decrypt - low-level signature operations
6
7=head1 SYNOPSIS
8
9 #include <openssl/rsa.h>
10
11The following functions have been deprecated since OpenSSL 3.0, and can be
12hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
13see L<openssl_user_macros(7)>:
14
15 int RSA_private_encrypt(int flen, unsigned char *from,
16                         unsigned char *to, RSA *rsa, int padding);
17
18 int RSA_public_decrypt(int flen, unsigned char *from,
19                        unsigned char *to, RSA *rsa, int padding);
20
21=head1 DESCRIPTION
22
23Both of the functions described on this page are deprecated.
24Applications should instead use L<EVP_PKEY_sign_init_ex(3)>,
25L<EVP_PKEY_sign(3)>, L<EVP_PKEY_verify_recover_init(3)>, and
26L<EVP_PKEY_verify_recover(3)>.
27
28These functions handle RSA signatures at a low-level.
29
30RSA_private_encrypt() signs the B<flen> bytes at B<from> (usually a
31message digest with an algorithm identifier) using the private key
32B<rsa> and stores the signature in B<to>. B<to> must point to
33B<RSA_size(rsa)> bytes of memory.
34
35B<padding> denotes one of the following modes:
36
37=over 4
38
39=item RSA_PKCS1_PADDING
40
41PKCS #1 v1.5 padding. This function does not handle the
42B<algorithmIdentifier> specified in PKCS #1. When generating or
43verifying PKCS #1 signatures, L<RSA_sign(3)> and L<RSA_verify(3)> should be
44used.
45
46=item RSA_NO_PADDING
47
48Raw RSA signature. This mode should I<only> be used to implement
49cryptographically sound padding modes in the application code.
50Signing user data directly with RSA is insecure.
51
52=back
53
54RSA_public_decrypt() recovers the message digest from the B<flen>
55bytes long signature at B<from> using the signer's public key
56B<rsa>. B<to> must point to a memory section large enough to hold the
57message digest (which is smaller than B<RSA_size(rsa) -
5811>). B<padding> is the padding mode that was used to sign the data.
59
60=head1 RETURN VALUES
61
62RSA_private_encrypt() returns the size of the signature (i.e.,
63RSA_size(rsa)). RSA_public_decrypt() returns the size of the
64recovered message digest.
65
66On error, -1 is returned; the error codes can be
67obtained by L<ERR_get_error(3)>.
68
69=head1 SEE ALSO
70
71L<ERR_get_error(3)>,
72L<RSA_sign(3)>, L<RSA_verify(3)>,
73L<EVP_PKEY_sign(3)>, L<EVP_PKEY_verify_recover(3)>
74
75=head1 HISTORY
76
77Both of these functions were deprecated in OpenSSL 3.0.
78
79=head1 COPYRIGHT
80
81Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
82
83Licensed under the Apache License 2.0 (the "License").  You may not use
84this file except in compliance with the License.  You can obtain a copy
85in the file LICENSE in the source distribution or at
86L<https://www.openssl.org/source/license.html>.
87
88=cut
89