Experts: You can use Bitcoin with confidence, quantum computers cannot defeat SHA-2 encryption technology

Are you still worried that your Bitcoin will be threatened by future quantum computers? According to research by computer experts, this worry is completely unnecessary.

Some people speculate that current encryption techniques will fail once quantum computers appear, but experts who oppose this view assert that hash functions and asymmetric encryption can not only protect modern computers, but also block attacks from future quantum computers.

Matthew Amy from the University of Waterloo in Canada presented this view at the International Association for Cryptologic Research.

Amy and researchers from the Perimeter Institute for Theoretical Physics and the Canadian Institute for Advanced Research carefully reviewed attacks on SHA-2 and SHA-3 using the Grover algorithm.

Note: (1) Grover: In 1995, Grover LK proposed the quantum Grover algorithm for “finding a number that satisfies a condition in a set of unordered numbers”.

(2) SHA-2: SHA, the Secure Hash Algorithm, is a cryptographic hash function designed by the National Security Agency (NSA) of the United States. SHA-2 and SHA-3 are members of the SHA family.

Grover's algorithm is a quantum algorithm that can produce specific predictable input and output values ​​in a way that has a high probability of being input.

"Grover's algorithm can crack a 128-bit symmetric key in about 264 iterations (repeated calculations)," Wikipedia says, "or a 256-bit password in about 2128 iterations. Therefore, some people have suggested doubling the length of the symmetric key to prevent attacks by future quantum computers."

The researchers estimate that cracking SHA-256 and SHA3-256 would require 2166 "logical qubit cycles," so the report says quantum computers won't pose much of a threat, though some classical processors will be needed to manage them.

Note: (1) qubit: quantum bit. A quantum bit is a unit vector in the complex two-dimensional Hilbert space.

The report states: “The difficulty in overcoming hash functions is that the coherence time of physical qubits is limited. Noise in physical systems will eventually corrupt long-term computing states. If logically qubits are to be kept in an active processing state at all times, then regular evaluation and correction procedures for error detection are required.”

Note: (1) Coherence time: refers to the maximum time difference range within which the channel remains constant. The same signal from the transmitter reaches the receiver within the coherence time, and the fading characteristics of the signals are completely similar. The receiver considers it to be one signal.

Using ASICs (application-specific integrated circuits) can run millions of hashes per second, but using the Grover algorithm to crack SHA-256 or SHA3-256 would still take 10^32 years. This is longer than the existence of the universe.

Register added: “Even if you don’t care how much space the circuitry takes up and you use a Bitcoin mining ASIC chip that runs a billion hashes per second, that’s still a long time to crack, about 10^29 years.”

These hash functions represent mathematical operations performed on numbers, which means that the hash functions are highly "collision-resistant" and an attacker cannot use two different input values ​​to derive the same hash output value. The SHA-2 family consists of 6 hash functions: SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224, SHA-512/256.

SHA-256 and SHA-512 are very new hash functions. The former defines a word as 32 bits, while the latter defines a word as 64 bits.