Pidgin-paranoia is a plugin for Pidgin (formerly known as Gaim) that provides information-theoretically secure encrypted conversations using one-time pads. Because the plugin uses a one-time pad where the secret key has the same length as the message and the key is only used once, the encryption is information-theoretically secure. This means that from the encrypted messages the contents of the messages are not revealed. In short: If you use truly random numbers to generate the key files, and if you keep them perfectly secret, one-time pads can not be broken.
The Off-the-Record (OTR) Messaging proxy is a multi- platform proxy that allows you to have private conversations using the AIM client of your choice. It provides encryption, which prevents someone who intercepts your instant messages from reading them, authentication, which ensures that the correspondent is who you think it is, and perfect forward secrecy, which ensures that no previous conversation is compromised if you lose control of your private keys.
Whisper IM is a secure IM client that provides end-to-end encryption over a XMPP/Jabber network. The encryption system (The Whisper Protocol) is designed for instant messaging, and is IM protocol and platform neutral. It supports all standard instant messaging features, such as messages, one to one chat, and online presence. The user interface is clean and easy to use. It also features multi-user chat (JEP45), context sensitive help, a service discovery tool (JEP30), and internationalization support.
Off-the-Record (OTR) Messaging is a gaim plugin which allows you to have private conversations over the instant messaging system of your choice. It provides encryption, which prevents someone who intercepts your instant messages from reading them; authentication, which ensures that the correspondent is who you think it is; and perfect forward secrecy, which ensures that no previous conversation is compromised if you lose control of your private keys.
KDX is a powerful cross-platform BBS-style encrypted Internet communications system that provides messaging, news, file and folder transfer, voice chat (Internet Telephone), text chat, remote access, trackers, and more. It uses strong encryption to protect communications for security and privacy. It is useful for groups that need to collaborate on a project via the Internet. It is also very useful for remote administration of a computer. It uses a client/server architecture.