Scientists estimate that quantum computers may become powerful enough to crack the Bitcoin encryption in a decade
Quantum computers are now a thing and many research teams across the world are competing to constantly improve the efficiency and computing power of this new breed of number crunching machines. Back in the mid-2010s, when most researchers were pushing for quantum supremacy over traditional computers, some pointed out that qubits may eventually be used to crack the most sophisticated encryption algorithms in existence, including the SHA-256 one used by cryptocurrencies like Bitcoin. This realization was recently reinforced by Mark Webber and the Ion Quantum Technology team of scientists from the University of Sussex, who calculated what it really takes to break the Bitcoin encryption system and a ballpark estimate of when that could happen.
The SHA (Secure Hash Algorithm) cluster of cryptographic functions was created by the US NSA in the early 2000s. Bitcoin uses the 256-bit version to encrypt all transactions that need to be verified by the mining network before their addition to the blockchain. This is also called proof-of-work consensus because the miners essentially validate how the bitcoin amounts coming from each block are distributed based on the contribution to cracking the cryptographic key assigned to each transaction. The miner or group of miners who succeeds in cracking the key first claims the majority of the bitcoin rewarded per block.
Webber and his team calculated that the fastest quantum computer currently online deployed by IBM with a processing power of 127 qubits is still far from cracking the SHA-256 algorithm in a reasonable time frame. In order to lower the time frame to around 1 hour, the quantum computer would need to harness the power of 317 million qubits, but that will still not be nearly enough to fully crack the code. As Webber puts it, “the transactions get announced and there’s a key associated with that transaction. There’s a finite window of time when that key is vulnerable and that varies, but it’s usually around 10 minutes to an hour, maybe a day.” Cracking the code in a 10-minute window actually requires a processor with 1.9 billion qubits.
IBM is confident that it can exponentially increase the qubit number in the next few years, and we could see a processor with millions of qubits in at most 5 years, but reaching billions of qubits may take double that time. There is no immediate threat for the Bitcoin network, yet core developers should consider upgrading the encryption code to make it quantum-resistant by the end of this decade.