openssl/doc/crypto/RSA_sign.pod

=pod

=head1 NAME

RSA_sign, RSA_verify - RSA signatures

=head1 SYNOPSIS

 #include <openssl/rsa.h>

 int RSA_sign(int type, const unsigned char *m, unsigned int m_len,
    unsigned char *sigret, unsigned int *siglen, RSA *rsa);

 int RSA_verify(int type, const unsigned char *m, unsigned int m_len,
    unsigned char *sigbuf, unsigned int siglen, RSA *rsa);

=head1 DESCRIPTION

RSA_sign() signs the message digest B<m> of size B<m_len> using the
private key B<rsa> as specified in PKCS #1 v2.0. It stores the
signature in B<sigret> and the signature size in B<siglen>. B<sigret>
must point to RSA_size(B<rsa>) bytes of memory.
Note that PKCS #1 adds meta-data, placing limits on the size of the
key that can be used.
See L<RSA_private_encrypt(3)|RSA_private_encrypt(3)> for lower-level
operations.

B<type> denotes the message digest algorithm that was used to generate
B<m>. It usually is one of B<NID_sha1>, B<NID_ripemd160> and B<NID_md5>;
see L<objects(3)|objects(3)> for details. If B<type> is B<NID_md5_sha1>,
an SSL signature (MD5 and SHA1 message digests with PKCS #1 padding
and no algorithm identifier) is created.

RSA_verify() verifies that the signature B<sigbuf> of size B<siglen>
matches a given message digest B<m> of size B<m_len>. B<type> denotes
the message digest algorithm that was used to generate the signature.
B<rsa> is the signer's public key.

=head1 RETURN VALUES

RSA_sign() returns 1 on success, 0 otherwise.  RSA_verify() returns 1
on successful verification, 0 otherwise.

The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.

=head1 BUGS

Certain signatures with an improper algorithm identifier are accepted
for compatibility with SSLeay 0.4.5 :-)

=head1 CONFORMING TO

SSL, PKCS #1 v2.0

=head1 SEE ALSO

L<ERR_get_error(3)|ERR_get_error(3)>, L<objects(3)|objects(3)>,
L<rsa(3)|rsa(3)>, L<RSA_private_encrypt(3)|RSA_private_encrypt(3)>,
L<RSA_public_decrypt(3)|RSA_public_decrypt(3)> 

=head1 HISTORY

RSA_sign() and RSA_verify() are available in all versions of SSLeay
and OpenSSL.

=cut