Cryptography Reference
In-Depth Information
7. The return data follows the same chain in reverse. Each AIP
uses the session key to encrypt the data.
8. The computer strips away the
n
layers.
Zero Knowledge refers to this process as
telescope encryption
.The
actual process is more involved and sophisticated. Providing ade-
quate performance while doing so much encryption is not an easy
trick.
10.4.2 PipeNet
PipeNet is another anonymous network created by Wei Dai. It also
rests on a network of computers that route encrypted packets. The
principle difference lies in the synchronized mechanism for coordi-
nating the flowof the packets. At each clock step, all of the computers
in the network receive a packet, perform the necessary encryption,
and then pass it on. If a packet does not arrive, one is not sent.
This solution prevents an omniscient attacker from watching the
flow of all of the packets in the hope to figuring out who is commu-
nicating with whom. In the Freedom network, a heavy user may in-
advertantly give away their path by shipping a large amount of data
along it. The omniscient attacker may not be able to break the en-
cryption, but jus counting the size of the packets could reveal the
destination. Ideally, a large user base would provide enough cover.
The PipeNet's strict process for sending information ensures that
each link between machines only carries the same amount of infor-
mation at each step. The data moves along the chain in a strictly
choreographed process like soldiers marching across the square.
This process, however, has its own weaknesses. If one packet is
destroyed or one node in the network locks up, the entire chain shuts
down. If data doesn't arrive, it can't go out. [BMS01]
10.4.3 Crowds
The Crowds tool developed by Michael Reiter and Aviel D. Rubin
offers a good mechanism for webbrowsing that provides some of the
same anonymity as the FreedomNetwork or PipeNet, but without as
much security. It's simplicity, however, makes it easy to implement
and run. [RR98]
The protocol is very simple. Each computer in the network ac-
cepts a URL request for a document on the web and it makes a ran-
dom choice to either satisfy the request or pass it along to another
randomly selected user. If you want to see a document, your request
