Astoria - new Tor client designed to be more resistant to timing attacks

[Jesse Taylor]

Curious to hear your thoughts on this 
<http://www.dailydot.com/politics/tor-astoria-timing-attack-client/>:

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/With the threat of powerful intelligence agencies, like the////NSA 
<http://dailydot.com/tags/nsa>//, looming large, researchers have built 
a new////Tor <http://dailydot.com/tags/tor>////client called////Astoria 
<http://arxiv.org/pdf/1505.05173.pdf>////designed specifically to make 
eavesdropping harder for the world's richest, most aggressive, and most 
capable spies.//
////
//Tor, the world’s most popular anonymity network, works like this: A 
user fires up the client and connects to the network through what's 
called an entry node. To reach a website anonymously, the user’s 
Internet traffic is then passed encrypted through a so-called middle 
relay and then an exit relay (and back again). That user-relay 
connection is called a circuit. The website on the receiving end doesn’t 
know who is visiting, only that a faceless Tor user has connected.////An 
eavesdropper shouldn’t be able to know who the Tor user is either, 
thanks to the encrypted traffic being routed through 6,000 nodes in the 
network.////But something called "timing attacks" change the situation. 
When an adversary takes control of both the entry and exit relays, 
research shows they can potentially deanonymize Tor users //within 
minutes <http://arxiv.org/abs/1503.03940>//.//

////A full 58 percent of Tor circuits are vulnerable to network-level 
attackers, such as the NSA or Britain’s Government Communications 
Headquarters (GCHQ), when they access popular websites, according to 
new////research <http://arxiv.org/pdf/1505.05173.pdf>////from American 
and Israeli academics. Chinese users are the most vulnerable of all to 
these kinds of attacks, with researchers finding 85.7 percent of all Tor 
circuits from the country to be vulnerable.//
////
//Even though Tor is designed to provide complete anonymity to its 
users, the NSA’s position means they can potentially see and measure 
both traffic entering the Tor network and the traffic that comes out. 
When an intelligence agency can see both,//simple statistics 
<http://freehaven.net/anonbib/#danezis:pet2004>////help an autonomous 
system at their control match the data up in a timing attack and 
discover the identity of the sender.////Anonymity over.////This kind of 
threat has been known to Tor developers for over a decade. They’ve been 
trying to make eavesdropping difficult for spy agencies for just as long.//
////
//To counter the threat, American-Israeli researchers built Astoria, a 
new Tor client focused on defeating autonomous systems that can break 
Tor’s anonymity.////Astoria reduces the number of vulnerable circuits 
from 58 percent to 5.8 percent, the researchers say. The new solution is 
the first designed to beat even the most//recently 
<http://arxiv.org/abs/1503.03940>////proposed 
<http://dl.acm.org/citation.cfm?id=2673869>////asymmetric correlation 
attacks on Tor.//
////
//Designed to beat such attacks, Astoria differs most significantly from 
Tor's default client in how it selects the circuits that connect a user 
to the network and then to the outside Internet. The tool, at its 
foundation, is an algorithm designed to more accurately predict attacks 
and then securely select relays that mitigate timing attack 
opportunities for top-tier adversaries.//
////
//Astoria adroitly considers how circuits should, according to the 
researchers, be made “when there are no safe possibilities,” how to 
safely balance the growing bandwidth load across the Tor network, and 
how to keep Tor’s performance “reasonable” and relatively fast even when 
Astoria is in its most secure configuration.////All this while under the 
unblinking gaze of the world’s best intel services.////Defeating timing 
attacks against Tor completely isn’t possible because of how Tor is 
built, but making the attacks more costly and less likely to succeed is 
a pastime that Tor developers have dedicated a decade to. Astoria 
follows in those footsteps.////By choosing relays based on lowering the 
threat of eavesdropping by autonomous systems and then choosing randomly 
if no safe passage is possible, Astoria aims to minimize the information 
gained by an adversary watching an entire circuit.//
////
//“In addition to providing high-levels of security against such 
attacks, Astoria also has performance that is within a reasonable 
distance from the current Tor client,” the researchers wrote. “Unlike 
other AS-aware Tor clients, Astoria also considers how circuits should 
be built in the worst case—i.e., when there are no safe relays that are 
available. Further, Astoria is a good network citizen and works to 
ensure that the all circuits created by it are load-balanced across the 
volunteer driven Tor network.”//
////
//In an upgrade aimed at making Tor even more usable for the average 
person, the newest Tor Browser allows a sliding scale of security that 
balances speed and usability with strong security 
preferences.////Similarly, Astoria provides multiple security options. 
However, it's both most effective and most usable when at its highest 
security level, the researchers say, so "Astoria is a usable substitute 
for the vanilla Tor client only in scenarios where security is a high 
priority."/

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Source: http://www.dailydot.com/politics/tor-astoria-timing-attack-client/
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