we cant use no. 2 because that means even users who have already unsubscribed but still has the list server's public key can still decrypt the mail messages she intercepted from current subscribers.
i guess the most server-efficient method to distribute encrypted mails to its subscriber would be to generate a single session key for each new message. use the session key to encrypt the new message. the resulting encrypted msg will be the only copy to be sent to all subscribers. this eliminates having to run the symmetric cipher over the message for N times (N = no. of subscribers.) it also wouldnt matter now to use a slow but powerful symmetric cipher because it's only done once per new message. the only operation which will be repeated for each subscriber would be, encrypting the session key (and probably a message digest) using each subscriber's public key. pong On Fri, 23 Nov 2001, Pablo Manalastas wrote: > (2) The list server can encrypt the message using its private key. > When the member receives the message, he then decrypts it using > the servers public key, which he has possession of. > > Yes. > > Actually, it is much more complicated than this. Encrypting/decrypting > using PGP public/private keys is expensive, since it involves raising > to powers and modular arithmetic. To save time PGP/GPG/openssl > will generate a session key with which it encrypts the message by > addition (decryption will be subtraction?). Then the session key > is sent encrypted with the the PGP/GPG/openssl key. The session key > is usually small (1024 bytes), so PGP-encrypting it does not take > too much time. Then the session-key encrypted message and the > PGP-encrypted session key are both sent to the recipient. > > PMana > _ Philippine Linux Users Group. Web site and archives at http://plug.linux.org.ph To leave: send "unsubscribe" in the body to [EMAIL PROTECTED] To subscribe to the Linux Newbies' List: send "subscribe" in the body to [EMAIL PROTECTED]
