Re: Reverse Encryption in .NET

From: james chou (jameschou2000_at_yahoo.com)
Date: 02/27/04 

Date: Thu, 26 Feb 2004 17:59:03 -0800

Thanks for your reply. As I understand, one way to authenticate a client
is to have server use client's public key to decrypt a token that is
encrypted with client's private key. That is exactly how a signature is
generated and verified except signature is generated by encrypting a
digest of a message. If a private key can be used to encrypt a digest of
a message, why can it be used to encrypt the message? I believe it is
technically possible. As matter of fact, I even found a well known
commercial PKI product that can do that. However, Windows cryptoAPI and
Java JCE(with default provider) don't provide this capability.

To keep the private key at server and distribute the public key to
clients doesn't seem to work. Every client can use the public key to
encrypt something and server will be able to decrypt it with no
problems. The server won't be able to tell which client is which unless
we have a keypair for each client. Since the public key is a public
information, everyone including unauthorized users can get it and use it
to access the server.

For my usage, looks like the signature will do it. However, I am
interested to the reason why reverse encryption is not provided in
Windows CryptoAPI and Java JCE.

Again, thanks for your information. Really appreciate that.

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