Ecafe Mixmaster Remailer wrote:
The proposal for a Hackerpunks nym based mailing list is interesting, however, there are some concerns regarding the susceptibility of the list to traffic analysis.
I think that the belief of the owner of hackerpunks that s/he won't be discovered is somewhat naive. Even though your traffic analysis ideas are right (see below), the most likely way to discover the owner is his/her unintentional screwup. I just feel like monitoring traffic of all internet is too expensive. Still, the secrecy of the location of the hackerpunks-owner is not such an important thing (as long as the list is not located in some police state not honoring free speech). The knowledge of said localtion is not even really important since the contents of this list may be montored anyway by simply subscribing to the list.
The solution to the two dilemmas seems to be to ask that the C2 re-mailing code be modified so as ensure that each messages is padded to a fixed size before encrypting and being sent through the reply block. On the other hand, this would give away information that anyone receiving messages of this fixed length was likely the owner of some C2 nym.
[maybe I saw it on this list] How about this: that every remailer adds a cookie of size X where S == size( message ) X == 20KB - S + rand( 40KB ) if S < 20KB X == 40KB - S + rand( 80KB ) if 20KB <= S < 40KB X == 80KB - S + rand( 160KB ) if 40KB <= S < 80KB and so on. This way, only 2-3 bits of information about size will be available to traffic analyzers, instead of about 10-12. For the most typical situation of messages being about 5KB in size, there is no information leaking. Of course, if an incoming message contained a cookie, it should be dropped by the remailer to be replaced by the new one on the next hop. Same cookie feature could be added to premail. Have fun.