Quantum computers vs. crypto mining: Separating facts from fiction

(CoinDesk)  Ollie Leach,  Learn editor for the Crypto Explainer+, has written a thorough review discussing whether quantum computers could eventually be directed at crunching crypto mining computations required to generate new blocks.  Inside Quantum summarizes here.

Leach acknowledges the growing fears that quantum computers could eventually be directed at crunching crypto mining computations required to generate new blocks. Those wielding quantum computers could, in theory, gain a significant advantage over every other miner in the blockchain network, threatening the decentralization and security of proof-of-work blockchains like Bitcoin and Litecoin. Not to mention, earning a vast majority of the remaining block rewards

A recently published academic paper in AVS Quantum Science entitled “The impact of hardware specifications on reaching quantum advantage in the fault tolerant regime” outlined two key threats posed by quantum computing to crypto mining, specifically bitcoin (BTC) mining, and the wider ecosystem:
–Threat to the proof-of-work consensus mechanism.
–Threat to the elliptic curve encryption of digital signatures.

The proof-of-work consensus mechanism refers to the special system certain blockchains employ to select honest participants to perform the important role of proposing new blocks of transaction data to be added to the blockchain. Because there is no single authority governing a blockchain, it must rely on an automated system coded into the protocol to filter out dishonest users who might attempt to corrupt the blockchain with invalid transactions.
Quantum computers have the capacity to perform higher calculations than other types of specialized machines, and so the obvious concern is they could dominate the mining-based competition. According to the paper’s authors, however, that threat is considered to be minimal because of the nature of the considerably slower clock cycle time of quantum computers versus application-specific integrated circuit (ASIC) miners

In fact, computer scientists in another academic paper entitled “Vulnerability of blockchain technologies to quantum attacks,” which was published in ScienceDirect, suggested it may take as long as to the year 2028 before quantum computers are sophisticated enough to outcompete current ASIC chip technology and perform a majority attack on a blockchain network.

Both papers concurred that the largest threat posed by quantum computers to crypto is not to mining but by breaking the “Elliptic Curve Digital Signature Algorithm,” or ECDSA, which is used by bitcoin and a vast majority of other leading cryptocurrencies.
ECDSA is the cryptographic system used to generate mathematically linked public-private keys – the digital tools needed to send and receive cryptocurrency as well as prove who owns the assets held within a crypto wallet.
“If the same public/private key pair is used to hold the users’ bitcoin after the public key becomes public knowledge, then all funds secured by the key pair will be vulnerable. However, it must also be considered that bitcoin wallets tend to not repeatedly use the same key pairs,” according to the paper in AVS Quantum Science.
So how many qubits would it take to break the elliptic curve algorithm? According to the AVS Quantum Science paper, quite a lot:
“… It would require 317 × 106 physical qubits to break the encryption within one hour with a code cycle time of 1 μs. To break it within 10 min with the same code cycle time, it would require 1.9 × 109 physical qubits, whereas to break it within 1 day, it would require only 13 × 106 physical qubits.”

Main problems facing quantum computing technology:
While quantum computers are already a thing, the technology is still very much in its infancy.
IBM’s quantum processor, dubbed “Eagle,” is considered the world’s most powerful quantum computing system to date – containing 127 qubits. A long way off from the estimated 1.9 billion qubits required to break ECDSA within 10 minutes.
Adding more qubits is by no means as straightforward as it sounds, either. Sensitivity to external factors that significantly inhibits the progression of quantum computers and means they are unlikely to become a major threat to cryptocurrency mining or to the underlying cryptography that secures transactions until this issue is addressed.

As it stands, while quantum computers may one day possess the ability to severely undermine crypto mining and the integrity of blockchain-based networks, the current technology is far from being sophisticated enough to cause any serious concern.