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RSA_private_encrypt(3)              OpenSSL             RSA_private_encrypt(3)

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.

1.0.2h                            2016-05-03            RSA_private_encrypt(3)