Your understanding is flawed. Both keys can encrypt stuff that only the other key can decrypt. The public key is used to encrypt the data itself, so I can send you stuff securely. The private key can encrypt stuff, like a digital hash of the message, proving to a degree that you sent it (assuming you have secured your private key and no-one else has it).
Kurt Seifried, [EMAIL PROTECTED] A15B BEE5 B391 B9AD B0EF AEB0 AD63 0B4E AD56 E574 http://seifried.org/security/ http://www.idefense.com/digest.html
