What about Quantum Computing?

I got this question from a friend this week:

Will advancements in Quantum technology cause significant problems for crypto-currency?

He was curious after seeing this LinkedIn post:

Important news that will impact the distributed ledger community and particularly the entire discussion around custody. Post Quantum computing cryptography just had a giant step forward. This is incredibly important because Shor's algorithm allows quantum computers to factor integers very quickly and this can be used to crack specific private keys when the public key is known (this allows algebraic based cryptography to be cracked). This can obviously cause problems with a distributed ledger system or DeFi or crypto in general. This can not disrupt the ledger but can destroy certain consensus mechanisms for new blocks and attack specific wallets.

This was commentary on the news that NIST has selected four quantum-resistant algorithms to be included in its upcoming post-quantum cryptographic standard.

My answer:

That's a great question and an interesting article, thanks for sharing!

Short answer: No. There will be some short-term disruption but it won't fundamentally change the value proposition of cryptocurrencies.

Long answer: The cryptographic algorithms that modern cryptography uses (including but not limited to cryptocurrencies) depend on the problem of factoring very large integers into their prime factors. Up until now, that has been a highly compute intensive problem, making it impractical to break the codes.

Per the article, quantum computing may be turning factoring large integers into a trivial problem. Which means private keys that are secure today won't be whenever quantum computers are applied to cracking them.

But, this has been anticipated for a long time. As far back as 1990, when I was studying this as an undergrad, we were told "of course, if factoring large integers into primes becomes easy, all of these algorithms will become insecure"

So for once, the government has shown some foresight and NIST has called for development of quantum-resistant algorithms that use different hard mathematical problems than factoring large integers.

The designs of the major cryptocurrencies anticipate this problem and allow for the swapping in of new algorithms in case the current ones become insecure. This has happened before in computer security; with the compute power available today, cryptography that was safe 15 years ago is insecure today and those algorithms have been retired.

TL;DR

Quantum computers will make some cryptograhic algorithms obsolete, but won’t kill cryptocurrencies or other blockchain solutions.