http://arxiv.org/pdf/1410.6079v1.pdf "Abstract âBitcoin is a decentralized P2P digital currency in which coins are generated by a distributed set of miners and transaction are broadcasted via a peer-to-peer network. While Bitcoin provides some level of anonymity (or rather pseudonymity) by encouraging the users to have any number of random-looking Bitcoin addresses, recent research shows that this level of anonymity is rather low. This encourages users to connect to the Bitcoin network through anonymizers like Tor and motivates development of default Tor functionality for popular mobile SPV clients. In this paper we show that combining Tor and Bitcoin creates an attack vector for the deterministic and stealthy man-in-the-middle attacks. A low-resource attacker can gain full control of information flows between all users who chose to use Bitcoin over Tor. In particular the attacker can link together userâs transactions regardless of pseudonyms used, control which Bitcoin blocks and transactions are relayed to the user and can delay or discard userâs transactions and blocks. In collusion with a powerful miner double-spending attacks become possible and a totally virtual Bitcoin reality can be created for such set of users." Interesting quote: "Combining it with some peculiarities of how Tor handles data streams a stealthy and low-resource attacker with just 1-3% of overall Tor Exit bandwidth capacity and 1000-1500 cheap lightweight Bitcoin peers (for example, a small Botnet) can force all Bitcoin Tor traffic to go either through her Exit nodes or through her peers. This opens numerous attack vectors." a) Does this paper hold water? b) What is the price of 1-3% of all Tor Exit capacity and "1000-1500 cheap lightweight" Bitcoin peers?
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