Information faces Internet censorship from a user’s country of residence or the information’s desired destination. In addition, studies show censorship could occur in countries through which the data travels along its route.
Now, computer scientists at the University of Maryland have developed a method for providing concrete proof to Internet users their information did not cross through certain geographic areas.
This new system offers advantages over existing systems: It is immediately deployable and does not require knowledge of — or modifications to — the Internet’s routing hardware or policies.
“With recent events, such as censorship of Internet traffic, suspicious ‘boomerang routing’ where data leaves a region only to come back again, and monitoring of users’ data, we became increasingly interested in this notion of empowering users to have more control over what happens with their data,” said project lead Dave Levin, an assistant research scientist in the University of Maryland Institute for Advanced Computer Studies (UMIACS).
This new system’s name is Alibi Routing.
Information transmitted over the Internet, such as website requests or email content, breaks into packets and goes through a series of routers on the way to its destination. However, users have very little control over what parts of the world these packets traverse.
Some parts of the world have modified data returned to users, thus censoring content. In 2012, researchers demonstrated that Domain Name System (DNS) queries that merely pass through China’s borders are subject to the same risk as if the requests came from one of the country’s own residents.
To evaluate their Alibi Routing method, the researchers simulated a network with 20,000 participants and selected forbidden regions from the 2012 “Enemies of the Internet” report published by Reporters Without Borders — China, Syria, North Korea and Saudi Arabia — as well as the three other countries with the highest number of Internet users at the time of the study — the United States, China and Japan.
Alibi Routing works by searching a peer-to-peer network to locate “peers” — other users running the alibi routing software — that can relay a user’s packets to its ultimate destination while avoiding specified forbidden regions.
The peer ends up called an “alibi.” The alibi provides proof — calculations that exploit the fact information cannot travel faster than the speed of light — that at a particular time, a packet was at a specific geographic location sufficiently far enough away from the forbidden areas the data could not have entered them.
If successful, users receive proof their information reached its desired destination and it did not traverse the forbidden regions. Alternatively, the response could indicate the packets may have traversed forbidden areas.
Levin said the success rate for Alibi Routing depends on a few things, including how close the source and destination are to the forbidden region and how central the forbidden region is to Internet routing.
“There’s also a safety parameter that we use. Basically, it’s a way for users to select a desired level of confidence that the packet absolutely does not traverse the forbidden region,” Levin said. “The larger the safety parameter, the harder it is to find an alibi. The smaller the safety parameter, the easier it is to find an alibi.”
Based on simulated deployments, the system successfully found an alibi more than 85 percent of the time. With a small safety parameter, the success rate rose to 95 percent. The results suggest users can typically avoid the part of the world they wish to route around, Levin said.
Users do not always need an alibi, though. If two users are in the same room in Maryland and they want their information to avoid China, they don’t need an alibi to help them; they can just send the data directly to one another and measure the time it takes to do so.
“For some of the countries we tested, we only needed an alibi about one-third of the time” Levin said.
The team plans to release a version of Alibi Routing — likely as an Internet browser plug-in — for users to test by the end of 2015.
“The more participants this type of peer-to-peer system has in different geographical locations, the more useful it will be,” Levin said.