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.
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_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.
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).
SEE ALSO
ERR_get_error(3), RSA_meth_set_priv_dec(3), RSA_new(3), RSA_size(3)
STANDARDS
SSL, PKCS #1 v2.0
HISTORY
RSA_public_encrypt() and
RSA_private_decrypt() appeared in SSLeay 0.4 or
earlier and have been available since OpenBSD
2.4.
RSA_NO_PADDING is available since SSLeay
0.9.0. OAEP was added in OpenSSL 0.9.2b.
BUGS
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.