CryptoChat is an easy-to-use encrypted IRC (Internet Relay Chat) program, allowing you to talk to contacts just like any other instant messenger. According to Wikipedia, Internet Relay Chat is a form of real-time Internet text messaging (chat) or synchronous conferencing.

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How it Works

CryptoChat is the first EJC Cryptography product to feature public-key cryptography, and uses the Diffie-Hellman key exchange protocol to establish a random session key for communications.

Diffie-Hellman key exchange is a cryptographic protocol that allows two parties that have no prior knowledge of each other to jointly establish a shared secret key over an insecure communications channel. This key can then be used to encrypt subsequent communications using a symmetric key cipher.

In essence, this is how CryptoChat operates - a shared key is established using this method, and that key is then used to encrypt all messages sent over the IRC channel. The Blowfish algorithm is used as the symmetric key cipher.

The Diffie-Hellman protocol doesn't provide any authentication (ie. How do you know the person you are exchanging a key with is who they say they are?), and so all users of an encrypted channel need an identical authentication key (basically a password) to prove that they are 'authorized'.

The Clever Bit

The reason CryptoChat is so secure is that once you have finished using your encrypted channel, an attacker who has recorded every message sent cannot decrypt anything, even if you tell him the password. The security of this is due to something called the discrete log problem - find out more about this and the principles behind the Diffie-Hellman algorithm by clicking here.