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=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> using RSASSA-PKCS1-v1_5 as specified in RFC 3447. 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)> for lower-level
operations.

B<type> denotes the message digest algorithm that was used to generate
B<m>.
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.
RSA_verify() returns 1 on successful verification.

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

=head1 CONFORMING TO

SSL, PKCS #1 v2.0

=head1 SEE ALSO

L<ERR_get_error(3)>,
L<RSA_private_encrypt(3)>,
L<RSA_public_decrypt(3)>

=head1 COPYRIGHT

Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the "License").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file LICENSE in the source distribution or at
L<https://www.openssl.org/source/license.html>.

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