RSA_private_encrypt.pod revision 325335 
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, const unsigned char *from,
12    unsigned char *to, RSA *rsa, int padding);
13
14 int RSA_public_decrypt(int flen, const 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)|RSA_sign(3)> and L<RSA_verify(3)|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)|ERR_get_error(3)>.
59
60=head1 SEE ALSO
61
62L<ERR_get_error(3)|ERR_get_error(3)>, L<rsa(3)|rsa(3)>,
63L<RSA_sign(3)|RSA_sign(3)>, L<RSA_verify(3)|RSA_verify(3)>
64
65=head1 HISTORY
66
67The B<padding> argument was added in SSLeay 0.8. RSA_NO_PADDING is
68available since SSLeay 0.9.0.
69
70=cut
71