By many accounts, quantum computing (QC), which uses atomic “spin” instead of an electrical charge to represent its binary 1’s and 0’s, is evolving at
By many accounts, quantum computing (QC), which uses atomic “spin” instead of an electrical charge to represent its binary 1’s and 0’s, is evolving at an exponential rate. If QC is ever realized at scale, it could be a boon for human society, helping to improve crop yields, design better medicines and engineer safer airplanes, among other benefits.
The crypto sector could profit too. Just last week, for instance, a Bank of Canada-commissioned project simulated cryptocurrency adoption among Canadian financial organizations using quantum computing.
“We wanted to test the power of quantum computing on a research case that is hard to solve using classical computing techniques,” said Maryam Haghighi, director of data science at the Bank of Canada, in a press release.
But, others worry that quantum computing, given its extraordinary “brute force” power, could also crack blockchain’s cryptographic structure, which has served Bitcoin (BTC) so well since its inception. Indeed, some say it is only a matter of time before quantum computers will be able to identify the enormous prime numbers that are key constituents of a BTC private key — assuming no countermeasures are developed.
Along these lines, a recently published paper calculated just how much quantum power would be needed to duplicate a BTC private key, i.e., “the number of physical qubits required to break the 256-bit elliptic curve encryption of keys in the Bitcoin network,” as explained by the paper’s authors, who are associated with the University of Sussex.
To be sure, this will be no easy task. Bitcoin’s algorithm that converts public keys to private keys is “one way,” which means that it is easy to generate a public key from a private key but virtually impossible to derive a private key from a public key using present-day computers.
In addition, this would all have to be done in about 10 minutes, the average amount of time that a public key is exposed or vulnerable on the Bitcoin network. It also assumes that the public key is identical to the BTC address, as were most in Bitcoin’s early days before it became common practice to use the KECCAK algorithm to “hash” public keys to generate BTC addresses. It’s estimated that about one-quarter of existing Bitcoin is using unhashed public keys.
Given these constraints, the authors estimate that 1.9 billion qubits would be needed to penetrate a single Bitcoin private key within 10 minutes. Qubits, or quantum bits, are the analog to “bits” in classical computing. By comparison, most proto-QC computers today can summon up 50–100 qubits, though IBM’s state-of-the-art Eagle quantum processor can manage 127 qubits.
Put another way, that’s 127 qubits against the 1.9 billion needed to crack Bitcoin’s security using a large-scale trapped ion quantum computer, as proposed in the AVS Quantum Science paper.
Mark Webber, quantum architect at Universal Quantum, a University of Sussex spin-out firm, and the paper’s lead author, said, “Our estimated requirement […] suggests Bitcoin should be considered safe from a quantum attack for now, but quantum computing technologies are scaling quickly with regular breakthroughs affecting such estimates and making them a very possible scenario within the next 10 years.”
Is the threat real?
Could Bitcoin’s security really be cracked? “I think that quantum computers could break cryptocurrency,” Takaya Miyano, a professor of mechanical engineering at Japan’s Ritsumeikan University, told Cointelegraph, “Though, not in a few years time, but in 10–20 years time.”
Miyano recently lead a team that developed a chaos-based stream cipher designed to withstand attacks from large-scale quantum computers.
David Chaum, writing last year for Cointelegraph, also sounded the alarm — not only for crypto but for wider society as well:
“Perhaps most terrifying for a society so reliant on the internet, quantum-level computing puts all of our digital infrastructures at risk. Our contemporary internet is built on cryptography — the use of codes and keys to secure private communication and storage of data.”
Meanwhile, for cryptocurrencies like Bitcoin and Ether (ETH), “for whom this concept is fundamental, one sufficiently powerful quantum computer could mean the theft of billions of dollars of value or the destruction of an entire blockchain altogether,” continued Chaum.
There are more than 4 million BTC “that are potentially vulnerable to a quantum attack,” consulting firm Deloitte estimates, a number that comprises owners using un-hashed public keys or who are reusing BTC addresses, another unwise practice. At current market prices, that amounts to about $171 billion at risk.
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