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
11 int RSA_private_encrypt(int flen, unsigned char *from,
12                         unsigned char *to, RSA *rsa, int padding);
13
14 int RSA_public_decrypt(int flen, unsigned char *from,
15                        unsigned char *to, RSA *rsa, int padding);
16
17=head1 DESCRIPTION
18
19These functions handle RSA signatures at a low-level.
20
21RSA_private_encrypt() signs the B<flen> bytes at B<from> (usually a
22message digest with an algorithm identifier) using the private key
23B<rsa> and stores the signature in B<to>. B<to> must point to
24B<RSA_size(rsa)> bytes of memory.
25
26B<padding> denotes one of the following modes:
27
28=over 4
29
30=item RSA_PKCS1_PADDING
31
32PKCS #1 v1.5 padding. This function does not handle the
33B<algorithmIdentifier> specified in PKCS #1. When generating or
34verifying PKCS #1 signatures, L<RSA_sign(3)> and L<RSA_verify(3)> should be
35used.
36
37=item RSA_NO_PADDING
38
39Raw RSA signature. This mode should I<only> be used to implement
40cryptographically sound padding modes in the application code.
41Signing user data directly with RSA is insecure.
42
43=back
44
45RSA_public_decrypt() recovers the message digest from the B<flen>
46bytes long signature at B<from> using the signer's public key
47B<rsa>. B<to> must point to a memory section large enough to hold the
48message digest (which is smaller than B<RSA_size(rsa) -
4911>). B<padding> is the padding mode that was used to sign the data.
50
51=head1 RETURN VALUES
52
53RSA_private_encrypt() returns the size of the signature (i.e.,
54RSA_size(rsa)). RSA_public_decrypt() returns the size of the
55recovered message digest.
56
57On error, -1 is returned; the error codes can be
58obtained by L<ERR_get_error(3)>.
59
60=head1 SEE ALSO
61
62L<ERR_get_error(3)>,
63L<RSA_sign(3)>, L<RSA_verify(3)>
64
65=head1 COPYRIGHT
66
67Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
68
69Licensed under the OpenSSL license (the "License").  You may not use
70this file except in compliance with the License.  You can obtain a copy
71in the file LICENSE in the source distribution or at
72L<https://www.openssl.org/source/license.html>.
73
74=cut
75