RSA_public_encrypt, RSA_private_decrypt - RSA public key cryptography

#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);

`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.

`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.

SSL, PKCS #1 v2.0

ERR_get_error, rand, rsa, RSA_size

The **padding** argument was added in SSLeay 0.8. RSA_NO_PADDING is
available since SSLeay 0.9.0, OAEP was added in OpenSSL 0.9.2b.