Hi all, This message is primarily for Wei, but if anyone wants to contribute a response, please do....
Wei, in this post: http://www.mail-archive.com/[EMAIL PROTECTED]/msg01001.html you identify the lack of usefulness in encrypting with the private key and decrypting with the public key. Some experts in the sci.crypt usenet newsgroups have claimed that it's a relatively simple matter to derive the public key from the private key. If these experts are right, then I think encrypting with the private key and decrypting with the public key is a useful thing.... Here's the scenario: 1. A server wants to encrypt a short message for program PROG using RSA. PROG is a generally accessible program that anyone can download. 2. To decrypt messages, PROG must have the private key embedded in it. 3. Mallory has a copy of PROG. He finds the private key and derives the public key (somehow). 4. Mallory can now generate encrypted messages for any copy of PROG. However, if Crypto++ supported encryption using the private key and decryption with the public key, Mallory is stopped at step 3 (because it's hard to derive the public from the private key). Do you agree that this is a cryptographically useful scenario? Is there any alternative Asymmetric Cipher that would resolve this problem? -- Russell Robinson (mailto:[EMAIL PROTECTED]) Author of Tectite (CRM and Licensing for Software Developers) Download your free CRM from: http://www.tectite.com/ BTW, Wei, Love your work :-)
