5 RSA_private_encrypt, RSA_public_decrypt - Low level signature operations
9 #include <openssl/rsa.h>
11 int RSA_private_encrypt(int flen, unsigned char *from,
12 unsigned char *to, RSA *rsa,int padding);
14 int RSA_public_decrypt(int flen, unsigned char *from,
15 unsigned char *to, RSA *rsa,int padding);
19 These functions handle RSA signatures at a low level.
21 RSA_private_encrypt() signs the B<flen> bytes at B<from> (usually a
22 message digest with an algorithm identifier) using the private key
23 B<rsa> and stores the signature in B<to>. B<to> must point to
24 B<RSA_size(rsa)> bytes of memory.
26 B<padding> denotes one of the following modes:
30 =item RSA_PKCS1_PADDING
32 PKCS #1 v1.5 padding. This function does not handle the
33 B<algorithmIdentifier> specified in PKCS #1. When generating or
34 verifying PKCS #1 signatures, RSA_sign(3) and RSA_verify(3) should be
39 Raw RSA signature. This mode should I<only> be used to implement
40 cryptographically sound padding modes in the application code.
41 Signing user data directly with RSA is insecure.
45 The random number generator must be seeded prior to calling
46 RSA_private_encrypt().
48 RSA_public_decrypt() recovers the message digest from the B<flen>
49 bytes long signature at B<from> using the signer's public key
50 B<rsa>. B<to> must point to a memory section large enough to hold the
51 message digest (which is smaller than B<RSA_size(rsa) -
52 11>). B<padding> is the padding mode that was used to sign the data.
56 RSA_private_encrypt() returns the size of the signature (i.e.,
57 RSA_size(rsa)). RSA_public_decrypt() returns the size of the
58 recovered message digest.
60 On error, -1 is returned; the error codes can be
61 obtained by ERR_get_error(3).
65 err(3), rand(3), rsa(3), RSA_sign(3), RSA_verify(3)
69 The B<padding> argument was added in SSLeay 0.8. RSA_NO_PADDING is
70 available since SSLeay 0.9.0.