a state-owned quantum computer could break blockchains in as little as three years

26/11/19 A state-owned quantum computer could break blockchains in as little as three years

A commercially viable quantum computer is still probably a decade away but the first rudimentary, state-owned device capable of breaking common one-way encryption algorithms like AES and elliptic curve cryptography could be with us much sooner. Such a device would undoubtedly be clunky and challenging to apply to real-world problems, but not impossible given sufficient resources. And there’s a huge incentive for winning this race: whichever state manages to crack public key encryption will be “master of the world”, according to Andersen Cheng, CEO of London-based cryptography firm Post Quantum.

Among the early targets for decryption, after sensitive government documents, password caches and financial communications, will likely be bitcoin and other cryptocurrencies. That’s because the security of blockchains like bitcoin and ethereum depends on an Elliptic Curve Digital Signature Algorithm (ECDSA). The public key generated using ECSDA is used with a hashing algorithm to create the public address for sending and receiving the coin, while the corresponding private key is employed to sign digital transactions to verify that the originator of the transaction is genuine.

Blockchain pioneers like Ethereum’s Vitalik Buterin previously denied the quantum threat, stating that hashing function was sufficient to make transactions quantum-safe (he has since changed his tune), but this is only part of the picture, said Cheng. The problem does not lie with people stealing your private key from your cryptocurrency wallet, he said, rather it’s the weakness of the signature scheme which could allow a quantum computer operator to spoof the user by generating their private key from their public key and address.

“Once people know your cypher text they can start playing with it, then they can replicate your private key they can start signing transactions pretending they are you,” said…

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