Technical Details of BitTorrent Secure P2P Chat

BitTorrent has announced the technical details of the implementation of the cryptographically secure P2P service BitTorrent Chat, which is now in closed alpha testing . Its main advantage is the lack of a central server, so messages are sent directly from the sender to the subscriber’s device without intermediaries.

Only the destination is searched through the DHT network. For comparison, in traditional IM services, both the search for the addressee and the contents of the message are transmitted through a central server.



The public request for a cryptographically secure secure chat is stronger than ever. Various commercial companies are trying to implement it, and one should not forget that BitTorrent is also a commercial American company. However, they set a goal to create reliable technology that could become the standard for secure communications. “In the end, we realized that we have unique experience in creating such a platform,” the company writes in an official blog.

BitTorrent Chat will use asymmetric cryptography to protect user privacy. Moreover, the concept of “username” is not used at all, the system does not have an authorization procedure in the classical sense, with a username and password. Instead, each user generates a unique pair of secret and public key. For all users of the BitTorrent Chat network, you are your public key . In other words, you can use chat completely anonymously. Two users only need to exchange public keys to establish a secure communication channel.

Using asymmetric cryptography in P2P chat offers several advantages. The main thing is a reliable and convenient way to encrypt messages using a private key. The problem is that if someone retrieves your private key, they can decrypt the archive of old (and future) messages. Fortunately, BitTorrent has implemented a forward secrecy system. At the beginning of each conversation, a temporary cryptographic key is generated. It is created on the basis of your secret and public key, and after the conversation is deleted forever.

The key technology of BitTorrent Chat is DHT (distributed hash table) - a distributed hash table for translating public keys of users to IP addresses. Here it works the same way as in popular torrent clients like µTorrent. Recent versions of DHT support encryption to protect confidential information that is transmitted to the network. More about DHT see. Here .