Old Problem but still no avail

Question

hello..I'm trying on a program which encrypt some random bytes with secret key and then decrypt with a public key using RSA. However I encounter a problem is that it raises this error:
Exception in thread "main" java.security.InvalidKeyException: Can only encrypt w
ith an RSAPublicKey.
at javax.crypto.Cipher.init(DashoA6275)
So how can I encrypt some file using private key??
(THis scenario is like SSL.)
IF ultimately I can't do that, how can I implement the SSL operation??? I dun want to use other provider..
pls enlighten..thanks in advance

Answer 1

Sign a message means :
- get an hashcode of the message you sign
- encrypt this hashcode with the private key
Verify signature means :
- decrypt the signature with the public key
- get an hashcode of the message you sign
- compare the hashcode with the result of the decryption
with RSA key pairs you can crypt and decrypt with both public and private key.
You can use the private key to crypt, but it's very long.
You can exchange a session key in order to use a symetric algorithm to secure some data (like SSL protocal).
An ASN1 encoding of an hascode is quit similar to a symetric key bytes :
the RSA encryption will not be longer.