RSA_public_encrypt.pod revision 325337 
1=pod
2
3=head1 NAME
4
5RSA_public_encrypt, RSA_private_decrypt - RSA public key cryptography
6
7=head1 SYNOPSIS
8
9 #include <openssl/rsa.h>
10
11 int RSA_public_encrypt(int flen, const unsigned char *from,
12    unsigned char *to, RSA *rsa, int padding);
13
14 int RSA_private_decrypt(int flen, const unsigned char *from,
15     unsigned char *to, RSA *rsa, int padding);
16
17=head1 DESCRIPTION
18
19RSA_public_encrypt() encrypts the B<flen> bytes at B<from> (usually a
20session key) using the public key B<rsa> and stores the ciphertext in
21B<to>. B<to> must point to RSA_size(B<rsa>) bytes of memory.
22
23B<padding> denotes one of the following modes:
24
25=over 4
26
27=item RSA_PKCS1_PADDING
28
29PKCS #1 v1.5 padding. This currently is the most widely used mode.
30
31=item RSA_PKCS1_OAEP_PADDING
32
33EME-OAEP as defined in PKCS #1 v2.0 with SHA-1, MGF1 and an empty
34encoding parameter. This mode is recommended for all new applications.
35
36=item RSA_SSLV23_PADDING
37
38PKCS #1 v1.5 padding with an SSL-specific modification that denotes
39that the server is SSL3 capable.
40
41=item RSA_NO_PADDING
42
43Raw RSA encryption. This mode should I<only> be used to implement
44cryptographically sound padding modes in the application code.
45Encrypting user data directly with RSA is insecure.
46
47=back
48
49B<flen> must be less than RSA_size(B<rsa>) - 11 for the PKCS #1 v1.5
50based padding modes, less than RSA_size(B<rsa>) - 41 for
51RSA_PKCS1_OAEP_PADDING and exactly RSA_size(B<rsa>) for RSA_NO_PADDING.
52The random number generator must be seeded prior to calling
53RSA_public_encrypt().
54
55RSA_private_decrypt() decrypts the B<flen> bytes at B<from> using the
56private key B<rsa> and stores the plaintext in B<to>. B<to> must point
57to a memory section large enough to hold the decrypted data (which is
58smaller than RSA_size(B<rsa>)). B<padding> is the padding mode that
59was used to encrypt the data.
60
61=head1 RETURN VALUES
62
63RSA_public_encrypt() returns the size of the encrypted data (i.e.,
64RSA_size(B<rsa>)). RSA_private_decrypt() returns the size of the
65recovered plaintext.
66
67On error, -1 is returned; the error codes can be
68obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
69
70=head1 WARNING
71
72Decryption failures in the RSA_PKCS1_PADDING mode leak information
73which can potentially be used to mount a Bleichenbacher padding oracle
74attack. This is an inherent weakness in the PKCS #1 v1.5 padding
75design. Prefer RSA_PKCS1_OAEP_PADDING.
76
77=head1 CONFORMING TO
78
79SSL, PKCS #1 v2.0
80
81=head1 SEE ALSO
82
83L<ERR_get_error(3)|ERR_get_error(3)>, L<rand(3)|rand(3)>, L<rsa(3)|rsa(3)>,
84L<RSA_size(3)|RSA_size(3)>
85
86=head1 HISTORY
87
88The B<padding> argument was added in SSLeay 0.8. RSA_NO_PADDING is
89available since SSLeay 0.9.0, OAEP was added in OpenSSL 0.9.2b.
90
91=cut
92