NAME

       RSA_public_encrypt, RSA_private_decrypt - RSA public key cryptography

SYNOPSIS

        #include <openssl/rsa.h>

        int RSA_public_encrypt(int flen, unsigned char *from,
                               unsigned char *to, RSA *rsa, int padding);

        int RSA_private_decrypt(int flen, unsigned char *from,
                                unsigned char *to, RSA *rsa, int padding);

DESCRIPTION

       RSA_public_encrypt() encrypts the flen bytes at from (usually a session key) using the
       public key rsa and stores the ciphertext in to. to must point to RSA_size(rsa) bytes of
       memory.

       padding denotes one of the following modes:

       RSA_PKCS1_PADDING
           PKCS #1 v1.5 padding. This currently is the most widely used mode.

       RSA_PKCS1_OAEP_PADDING
           EME-OAEP as defined in PKCS #1 v2.0 with SHA-1, MGF1 and an empty encoding parameter.
           This mode is recommended for all new applications.

       RSA_SSLV23_PADDING
           PKCS #1 v1.5 padding with an SSL-specific modification that denotes that the server is
           SSL3 capable.

       RSA_NO_PADDING
           Raw RSA encryption. This mode should only be used to implement cryptographically sound
           padding modes in the application code.  Encrypting user data directly with RSA is
           insecure.

       flen must be less than RSA_size(rsa) - 11 for the PKCS #1 v1.5 based padding modes, less
       than RSA_size(rsa) - 41 for RSA_PKCS1_OAEP_PADDING and exactly RSA_size(rsa) for
       RSA_NO_PADDING.  The random number generator must be seeded prior to calling
       RSA_public_encrypt().

       RSA_private_decrypt() decrypts the flen bytes at from using the private key rsa and stores
       the plaintext in to. to must point to a memory section large enough to hold the decrypted
       data (which is smaller than RSA_size(rsa)). padding is the padding mode that was used to
       encrypt the data.

RETURN VALUES

       RSA_public_encrypt() returns the size of the encrypted data (i.e., RSA_size(rsa)).
       RSA_private_decrypt() returns the size of the recovered plaintext.

       On error, -1 is returned; the error codes can be obtained by ERR_get_error(3).

WARNING

       Decryption failures in the RSA_PKCS1_PADDING mode leak information which can potentially
       be used to mount a Bleichenbacher padding oracle attack. This is an inherent weakness in
       the PKCS #1 v1.5 padding design. Prefer RSA_PKCS1_OAEP_PADDING.

CONFORMING TO

       SSL, PKCS #1 v2.0

SEE ALSO

       ERR_get_error(3), RAND_bytes(3), RSA_size(3)

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 <https://www.openssl.org/source/license.html>.