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RSA_PUBLIC_ENCRYPT(3)		    OpenSSL		 RSA_PUBLIC_ENCRYPT(3)

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 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.
	   However, it is highly recommended to	use RSA_PKCS1_OAEP_PADDING in
	   new applications. SEE WARNING BELOW.

       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 not be	more than RSA_size(rsa)	- 11 for the PKCS #1 v1.5
       based padding modes, not	more than RSA_size(rsa)	- 42 for
       RSA_PKCS1_OAEP_PADDING and exactly RSA_size(rsa)	for RSA_NO_PADDING.
       When a padding mode other than RSA_NO_PADDING is	in use,	then
       RSA_public_encrypt() will include some random bytes into	the ciphertext
       and therefore the ciphertext will be different each time, even if the
       plaintext and the public	key are	exactly	identical.  The	returned
       ciphertext in to	will always be zero padded to exactly RSA_size(rsa)
       bytes.  to and from may overlap.

       RSA_private_decrypt() decrypts the flen bytes at	from using the private
       key rsa and stores the plaintext	in to. flen should be equal to
       RSA_size(rsa) but may be	smaller, when leading zero bytes are in	the
       ciphertext. Those are not important and may be removed, but
       RSA_public_encrypt() does not do	that. to must point to a memory
       section large enough to hold the	maximal	possible decrypted data	(which
       is equal	to RSA_size(rsa) for RSA_NO_PADDING, RSA_size(rsa) - 11	for
       the PKCS	#1 v1.5	based padding modes and	RSA_size(rsa) -	42 for
       RSA_PKCS1_OAEP_PADDING).	 padding is the	padding	mode that was used to
       encrypt the data.  to and from may overlap.

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. A return value of 0 is not an	error and means	only that the
       plaintext was empty.

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

WARNINGS
       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 2000-2019 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>.

1.1.1d				  2019-09-10		 RSA_PUBLIC_ENCRYPT(3)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | WARNINGS | CONFORMING TO | SEE ALSO | COPYRIGHT

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