3/25/2023 0 Comments Mit riffle![]() Generating and checking proofs is a computationally intensive process, however, which would significantly slow down the network if it had to be repeated with every message. Servers can then independently check for tampering. So with Riffle, users send their initial messages to not just the first server in the mixnet but all of them, simultaneously. Verifying the proof does require checking it against copies of the messages the server received. But the encryption can be done in such a way that the server can generate a mathematical proof that the messages it sends are valid manipulations of the ones it receives. Because of the onion encryption, the messages that each server forwards look nothing like the ones it receives it has peeled off a layer of encryption. To thwart message tampering, Riffle uses a technique called a verifiable shuffle. Then it would passively track the one message that doesn't follow its own prespecified route. If, for instance, an adversary that has commandeered a mixnet router wants to determine the destination of a particular message, it could simply replace all the other messages it receives with its own, bound for a single destination. This is not improbable in anonymity networks, where frequently the servers are simply volunteers' Internet-connected computers, loaded with special software. But it's vulnerable to active adversaries, which can infiltrate servers with their own code. Each server in the mixnet removes only one layer of encryption, so that only the last server knows a message's ultimate destination.Ī mixnet with onion encryption is effective against a passive adversary, which can only observe network traffic. Like many anonymity systems, Riffle also uses a technique known as onion encryption "Tor," for instance, is an acronym for "the onion router." With onion encryption, the sending computer wraps each message in several layers of encryption, using a public-key encryption system like those that safeguard most financial transactions online. It's this reshuffling of the messages that gives the new system its name: Riffle. The second server would permute them before sending them to the third, and so on.Īn adversary that had tracked the messages' points of origin would have no idea which was which by the time they exited the last server. If, for instance, messages from senders Alice, Bob, and Carol reach the first server in the order A, B, C, that server would send them to the second server in a different order-say, C, B, A. Each server permutes the order in which it receives messages before passing them on to the next. The heart of the system is a series of servers called a mixnet. ![]() The system devised by Kwon and his coauthors-his advisor, Srini Devadas, the Edwin Sibley Webster Professor of Electrical Engineering and Computer Science at MIT David Lazar, also a graduate student in electrical engineering and computer science and Bryan Ford SM '02 PhD '08, an associate professor of computer and communication sciences at the École Polytechnique Fédérale de Lausanne-employs several existing cryptographic techniques but combines them in a novel manner. But we also studied applications in microblogging, something like Twitter, where you want to anonymously broadcast your messages to everyone." "The reason is that things like honeypotting"-in which spies offer services through an anonymity network in order to entrap its users-"are a real issue. "The initial use case that we thought of was to do anonymous file-sharing, where the receiving end and sending end don't know each other," says Albert Kwon, a graduate student in electrical engineering and computer science and first author on the new paper. ![]() In experiments, the researchers' system required only one-tenth as much time as existing systems to transfer a large file between anonymous users. ![]() At the Privacy Enhancing Technologies Symposium in July, researchers at MIT's Computer Science and Artificial Intelligence Laboratory and the École Polytechnique Fédérale de Lausanne will present a new anonymity scheme that provides strong security guarantees but uses bandwidth much more efficiently than its predecessors. ![]()
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