Secure communication between multiple peers on a public channel

Question

I am wondering how can I secure communications between multiple peers over a public channel, like an IRC channel. With two peers it is easy - they exchange their encryption keys and decrypt the secret messages using their private keys, but how would this work with multiple peers without creating excessive duplication of messages? Is there some way to encrypt a message that would be readable by multiple peers not sharing the same secret key?

Answer 1

I believe CMS (Cryptographic Message Syntax) might solve this problem. It allows sender to encrypt a packet and multiple recipients to open it.

Basically it encrypts the contents with a random key and this key is encrypted for each recipient using various mechanisms.

Answer 2

CLAE is an asymmetric encryption algorithm that provides ultra security and the simplicity to share the secret keys with anyone, anywhere over the Internet. http://www.connectinprivate.com/clae.php

Answer 3

1. Generate a symmetric key
2. Encrypt symmetric key using public keys of all recipients, and broadcast (or provide on request from a client)
3. Transmit all user messages encrypted under the symmetric key

This means you only have one copy of the message (but you do have lots of copies of the encrypted symmetric key).

Of course you need to solve the key distribution problem first, to ensure you're only encrypting the symmetric key using authenticated public keys.