=pod

=head1 NAME

RSA_padding_add_PKCS1_type_1, RSA_padding_check_PKCS1_type_1,
RSA_padding_add_PKCS1_type_2, RSA_padding_check_PKCS1_type_2,
RSA_padding_add_PKCS1_OAEP, RSA_padding_check_PKCS1_OAEP,
RSA_padding_add_SSLv23, RSA_padding_check_SSLv23,
RSA_padding_add_none, RSA_padding_check_none - Asymmetric encryption
padding

=head1 SYNOPSIS

 #include <openssl/rsa.h>

 int RSA_padding_add_PKCS1_type_1(unsigned char *to, int tlen,
    unsigned char *f, int fl);

 int RSA_padding_check_PKCS1_type_1(unsigned char *to, int tlen,
    unsigned char *f, int fl, int rsa_len);

 int RSA_padding_add_PKCS1_type_2(unsigned char *to, int tlen,
    unsigned char *f, int fl);

 int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen,
    unsigned char *f, int fl, int rsa_len);

 int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
    unsigned char *f, int fl, unsigned char *p, int pl);

 int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
    unsigned char *f, int fl, int rsa_len, unsigned char *p, int pl);

 int RSA_padding_add_SSLv23(unsigned char *to, int tlen,
    unsigned char *f, int fl);

 int RSA_padding_check_SSLv23(unsigned char *to, int tlen,
    unsigned char *f, int fl, int rsa_len);

 int RSA_padding_add_none(unsigned char *to, int tlen,
    unsigned char *f, int fl);

 int RSA_padding_check_none(unsigned char *to, int tlen,
    unsigned char *f, int fl, int rsa_len);

=head1 DESCRIPTION

The RSA_padding_xxx_xxx() functions are called from the RSA encrypt,
decrypt, sign and verify functions.

They can also be called directly to implement padding for other
asymmetric ciphers. RSA_padding_add_PKCS1_OAEP() and
RSA_padding_check_PKCS1_OAEP() may be used in an application combined
with B<RSA_NO_PADDING> in order to implement OAEP with an encoding
parameter.

RSA_padding_add_xxx() encodes B<fl> bytes from B<f> so as to fit into
B<tlen> bytes and stores the result at B<to>. An error occurs if B<fl>
does not meet the size requirements of the encoding method.

The following encoding methods are implemented:

=over 4

=item PKCS1_type_1

PKCS #1 v2.0 EMSA-PKCS1-v1_5 (PKCS #1 v1.5 block type 1); used for signatures

=item PKCS1_type_2

PKCS #1 v2.0 EME-PKCS1-v1_5 (PKCS #1 v1.5 block type 2)

=item PKCS1_OAEP

PKCS #1 EME-OAEP

=item SSLv23

PKCS #1 EME-PKCS1-v1_5 with SSL-specific modification

=item none

simply copy the data

=back

The random number generator must be seeded prior to calling
RSA_padding_add_xxx().

RSA_padding_check_xxx() verifies that the B<fl> bytes at B<f> contain
a valid encoding for a B<rsa_len> byte RSA key in the respective
encoding method and stores the recovered data of at most B<tlen> bytes
at B<to>.

For RSA_padding_xxx_OAEP(), B<p> points to the encoding parameter
of length B<pl>. B<p> may be B<NULL> if B<pl> is 0.

=head1 RETURN VALUES

The RSA_padding_add_xxx() functions return 1 on success, 0 on error.
The RSA_padding_check_xxx() functions return the length of the
recovered data, -1 on error. Error codes can be obtained by calling
ERR_get_error(3).

=head1 SEE ALSO

RSA_public_encrypt(3), RSA_private_decrypt(3), RSA_sign(3), RSA_verify(3)

=head1 HISTORY

RSA_padding_add_PKCS1_type_1(), RSA_padding_check_PKCS1_type_1(),
RSA_padding_add_PKCS1_type_2(), RSA_padding_check_PKCS1_type_2(),
RSA_padding_add_SSLv23(), RSA_padding_check_SSLv23(),
RSA_padding_add_none() and RSA_padding_check_none() appeared in
SSLeay 0.9.0.

RSA_padding_add_PKCS1_OAEP() and RSA_padding_check_PKCS1_OAEP() were
added in OpenSSL 0.9.2b.

=cut