RSA_private_encrypt(3) OpenSSL RSA_private_encrypt(3)NAME
RSA_private_encrypt, RSA_public_decrypt - low level signature opera‐
tions
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 algorithmI‐
dentifier 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 cryp‐
tographically 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 VALUESRSA_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 ALSOERR_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 avail‐
able since SSLeay 0.9.0.
0.9.8k 2009-05-20 RSA_private_encrypt(3)
