Just wondering if http://www.tcpcrypt.org/ would be useful to add? Also is there any work being done to replace/add encryption at the ODI level?
This isn't a good idea.
- TCPCrypt is, and I can't stress this enough, absolute trash.
- It provides no protection against an active MITM attacker, it's not authenticated.
- The remote party too must support TCPCrypt, otherwise it won't work.
- Any remote party could just use TLS or an onion service and gain greater protection than that offered by TCPCrypt.
Tor cannot magically add crypto to traffic after leaves the network, it absolutely must be the responsibility of applications sending data over Tor to apply appropriate levels of cryptography to their communications, there is no alternative.