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.

1.0.1f                                             2014-01-06                          RSA_private_encrypt(3SSL)