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)|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