Quantum computers able to break bitcoin encryption will be “achievable” with “future advancements”, researchers say.
Researchers estimated the size a quantum computer would need to be to break the encryption of the bitcoin network as a test to see how large a quantum computer would need to be in the future to perform other tasks.
“The majority of existing work within this realm focuses on a particular hardware platform, superconducting devices, like those IBM and Google are working toward”, said Mark Webber, then of the University of Sussex, who led the research.
“Different hardware platforms will vary greatly on key hardware specifications, such as the rate of operations and the quality of control on the qubits”.
Quantum computers work by replacing traditional bits – the ‘1’s’ and ‘0’s’ used to encode digital information – with quantum bits, or qubits.
These can function as both a ‘1’ and a ‘0’ at the same time by existing in a state of superposition, meaning each new qubit added to the computer increases its power exponentially rather than linearly.
Many of the promises made by quantum computing will require an error-corrected quantum computer. This enables running longer algorithms by compensating for inherent errors inside the computer – at the cost of more physical qubits needed.
“To make the quantum algorithm run faster, we can perform more operations in parallel by adding more physical qubits. We introduce extra qubits as needed to reach the desired runtime, which is critically dependent on the rate of operations at the physical hardware level.”
Most quantum computers are limited because only the qubits next to one another can interact. In other designs, the qubits can be physically moved around to interact with others.
Quantum computers are better at breaking encryption than conventional computers. Most secure communication uses RSA (Rivest–Shamir–Adleman) encryption, first described in 1977.
The security of the system relies on the practical difficulty of factoring two large prime numbers, which are the basis of the public key. A message ‘locked’ by such a key can only be decoded if the receiver knows the prime numbers.
Bitcoin, by contrast, uses the elliptic curve digital signature algorithm, but researchers suggest that both methods will be vulnerable to an attack in the future.
“State-of-the-art quantum computers today only have 50-100 qubits”, said Webber. “Our estimated requirement of 30 [million] to 300 million physical qubits suggests Bitcoin should be considered safe from a quantum attack for now, but devices of this size are generally considered achievable, and future advancements may bring the requirements down further.’
Bitcoin may be able to perform a ‘hard-fork’ to a quantum-secure encryption technique, but the increased memory requirements could cause network scaling issues.
“The Impact of Hardware Specifications on Reaching Quantum Advantage in the Fault Tolerant Regime” was published in AVS Quantum Science.