A timestamp attack on Babel's anonymity

[Roger Dingledine <arma@mit.edu>]

I went looking in the Babel paper to see what its replay policy is.

|Section 8.6. Time Synchronization & Replay Detection
|
|As mentioned in Section 3.2.2, each layer of the onion created by Alice
|includes a time stamp. The value of the time stamp, referred to as \Theta,
|is the number of seconds elapsed in seconds since January 1, 1970 GMT,
|to the moment of message composition by the sender.

I can only assume that each layer of the onion has the same time stamp.

There probably aren't all that many people who compose a message on the
same second.

--Roger