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.
