The current state of anonymous file-sharing - Marc's Blog

5.4.2 End to End
Figure 9: Hop to Hop encryption
End to end encryption adds encryption from the source to the end. This keeps every
node besides the source and the destination from spying on the content of the data.
5.4.3 Problems with end to end encryption in anonymous networks
As Jason Rohrer, the inventor of the anonymous file-sharing software "Mute" 8 points
out in his paper dubbed "End-to-end encryption (and the Person-in-the-middle attacks)"
[21], using end-to-end encryption in an anonymous network poses a technical problem:
How can the sender get the receivers key to start the encrypted transfer in the first
place? In the majority of anonymous requests are routed over several nodes acting as
proxies (compare: Chapter 5.3). Each of those nodes could act as a "man in the middle"
and manipulate the exchanged keys. This would allow an arbitrary node to put in its
cryptographic keys and to read and re-encrypt the traffic for each of the endpoints of
the file-transfer.
On the internet, encrypted connections are usually established by using a trusted third
parties keys to verify the integrity of the person on the other end of your logical con-
nection. While this works perfectly fine on the internet, using this "trusted third party"
scheme on an anonymous network would compromise your anonymity by the necessity
to reveal your identity to the trusted third party. Even if that was somehow possible, it
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