On Fri, 23 Nov 2001, Juan Miguel Cacho wrote:
> The subscriber will then receive the list's pgp public key as part of the
> confirmation reply.
He will need the list's pgp public to encrypt his posting for
the list.
> The member will only need the lists pgp key to decode the message, but
> the list server will need all the members' keys to decode incoming
> messages.
The member will need his private key to decode/decrypt messages from the
list. The list server will need each member's public key to encode
messages for that member.
> It will then encode outgoing messages using server's key.
There are two ways to do this.
(1) The list server uses each member's public key to encrypt messages
for each member. When the member receives the message, he then
decrypts it with his private key. This method is expensive on the
part of the server, since if there are N members, it will have to
produce N distinct encrypted messages.
(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.
> Hey Wait, I think baliktad... now I'm confised... ;-<
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
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