Bitcoin, virtual money: User’s identity can be revealed much easier than thought

Bitcoin is the new money: minted and exchanged on the Internet. Faster and cheaper than a bank, the service is attracting attention from all over the world. But a big question remains: are the transactions really anonymous?

Several research groups worldwide have shown that it is possible to find out which transactions belong together, even if the client uses different pseudonyms. However it was not clear if it is also possible to reveal the IP address behind each transaction. This has changed: researchers have now demonstrated how this is feasible with only a few computers and about €1500.

“It’s hard to predict the future, but some people think that Bitcoin could do to finance what the Internet did to communications,” says Prof. Alex Biryukov, who leads digital currency research at the University. “So I think especially for Luxembourg it is important to watch what happens with Bitcoin.”

The Bitcoin system is not managed by a central authority, but relies on a peer-to-peer network on the Internet. Anyone can join the network as a user or provide computing capacity to process the transactions. In the network, the user’s identity is hidden behind a cryptographic pseudonym, which can be changed as often as is wanted. Transactions are signed with this pseudonym and broadcast to the public network to verify their authenticity and attribute the Bitcoins to the new owner.

In their new study, researchers at the Laboratory of Algorithmics, Cryptology and Security of the University of Luxembourg have shown that Bitcoin does not protect user’s IP address and that it can be linked to the user’s transactions in real-time. To find this out, a hacker would need only a few computers and about €1500 per month for server and traffic costs. Moreover, the popular anonymization network “Tor” can do little to guarantee Bitcoin user’s anonymity, since it can be blocked easily.

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