Bitmessage

Bitmessage implements a peer‑to‑peer communications protocol that delivers encrypted messages without relying on central authorities. The system is decentralized and trustless, using strong authentication to prevent sender spoofing and to conceal metadata such as sender and receiver identities from passive eavesdroppers. It is designed for one‑to‑one messaging as well as broadcast to multiple subscribers.

The reference client is open source under the MIT license and runs on macOS, Windows, and Linux, requiring PyQt and OpenSSL. Users can download pre‑built binaries or compile the Python source code from the repository, with step‑by‑step instructions provided for each platform. The project maintains a wiki, forum, and subreddit for community support and discussion.

Bitmessage is considered stable, though the developers note a recent remote‑code‑execution vulnerability that was patched in version 0.6.3.2 and advise users to upgrade. An independent security audit is still pending, and contributions are welcomed under the project's contribution guidelines.