Provided by: libssl-doc_1.1.0g-2ubuntu4_all

**NAME**

RSA_public_encrypt, RSA_private_decrypt - RSA public key cryptography

**SYNOPSIS**

#include <openssl/rsa.h> int RSA_public_encrypt(int flen, const unsigned char *from, unsigned char *to, RSA *rsa, int padding); int RSA_private_decrypt(int flen, const unsigned char *from, unsigned char *to, RSA *rsa, int padding);

**DESCRIPTION**

RSA_public_encrypt()encrypts theflenbytes atfrom(usually a session key) using the public keyrsaand stores the ciphertext into.tomust point to RSA_size(rsa) bytes of memory.paddingdenotes 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 shouldonlybe used to implement cryptographically sound padding modes in the application code. Encrypting user data directly with RSA is insecure.flenmust 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 callingRSA_public_encrypt().RSA_private_decrypt()decrypts theflenbytes atfromusing the private keyrsaand stores the plaintext into.tomust point to a memory section large enough to hold the decrypted data (which is smaller than RSA_size(rsa)).paddingis 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 byERR_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(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>.