Blockchains Vulnerable To Tampering, a DARPA Analysis Finds

A new report finds that blockchain systems might not be working as well as many crypto enthusiasts assume. From a report: The report was commissioned by the Defense Advanced Research Projects Agency, or DARPA, and the work was done by the software security research company Trail of Bits. Trail of Bits CEO Dan Guido says blockchain -- the public ledgers that keep track of cryptocurrencies, which are replicated on computers around the world -- isn't the egalitarian tech its advocates claim. "It's been taken for granted that the blockchain is immutable and decentralized, because the community says so," says Guido. But in practice, he says, these networks have evolved in ways that concentrate power in the hands of certain people or companies, including the large pools of "miners" whose computers earn virtual currency by maintaining the blockchains. Guido's team calls these potential situations "unintended centralities" -- situations in which someone gains leverage over the decentralized system, creating opportunities for tampering with the record of who owns what. Another example in the report of this kind of concentration is the fact that 60% of Bitcoin traffic is handled by just three internet service providers. "Let's say somebody with great top-down control of the internet in their country starts to interfere with that network," Guido says. By slowing down or stopping legitimate blockchain traffic, an attacker could become the "majority" voice in the consensus of what's written to a blockchain at that moment. "They can rewrite history. They can censor transactions. They can make it so that you can't spend your Bitcoin," says Guido. "It's definitely something people would want to do if they want to 'grief' the network."

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