What is "cryptocat"

Cryptocat is an open source desktop application intended to allow encrypted online chatting available for Windows, OS X, and Linux. It uses end-to-end encryption to secure all communications to other Cryptocat users. Users are given the option of independently verifying their buddies' device lists and are notified when a buddy's device list is modified and all updates are verified through the built-in update downloader.

Cryptocat is developed by Nadim Kobeissi and a community of open source contributors and is published under the terms of the GPLv3 license.