NAME¶
RSA_private_encrypt, RSA_public_decrypt - low level signature operations
SYNOPSIS¶
#include <openssl/rsa.h>
int RSA_private_encrypt(int flen, unsigned char *from,
unsigned char *to, RSA *rsa, int padding);
int RSA_public_decrypt(int flen, unsigned char *from,
unsigned char *to, RSA *rsa, int padding);
DESCRIPTION¶
These functions handle RSA signatures at a low level.
RSA_private_encrypt() signs the
flen bytes at
from (usually
a message digest with an algorithm identifier) using the private key
rsa and stores the signature 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 function does not handle the
algorithmIdentifier specified in PKCS #1. When generating or
verifying PKCS #1 signatures, RSA_sign(3) and RSA_verify(3)
should be used.
- RSA_NO_PADDING
- Raw RSA signature. This mode should only be used to implement
cryptographically sound padding modes in the application code. Signing
user data directly with RSA is insecure.
RSA_public_decrypt() recovers the message digest from the
flen
bytes long signature at
from using the signer's public key
rsa.
to must point to a memory section large enough to hold the message
digest (which is smaller than
RSA_size(rsa) - 11).
padding is the padding mode that was used to sign the data.
RETURN VALUES¶
RSA_private_encrypt() returns the size of the signature (i.e.,
RSA_size(rsa)).
RSA_public_decrypt() returns the size of the recovered
message digest.
On error, -1 is returned; the error codes can be obtained by
ERR_get_error(3).
SEE ALSO¶
ERR_get_error(3),
rsa(3),
RSA_sign(3),
RSA_verify(3)
HISTORY¶
The
padding argument was added in SSLeay 0.8. RSA_NO_PADDING is available
since SSLeay 0.9.0.