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...::::::::::Bit Torrent Protocol Encryption::::::::::...

Protocol encryption (PE) & Message stream encryption (MSE)

PE and MSE are protocol obfuscation methods, they use a D-H key exchange combined with the info hash of the torrent to establish the key, then it uses RC4 to encrypt the data.

The D-H key exchange helps to minimize the risk of passive listeners, and the info hash helps avoid man-in-the-middle attacks. RC4 is chosen for its speed. The first kilobyte of the RC4 output is discarded to prevent a particular attack.

The specification allows the users to choose between encrypting the headers only or the full connection. Encrypting the full connection provides more obfuscation but uses more CPU time.

However, only Azureus and µTorrent lets the user choose this.

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