Does Quantum Computing threaten crypto?

Wednesday 04 November 2015

Bitcoin is built on strong cryptography, but Quantum Computing could crack it like a walnut. Is this an issue for virtual currencies?

Quantum Computing (QC) has been talked about for years and the theory has been in place from the 1980s. Recently, though, the first experiments have successfully been undertaken that pave the way for working quantum computers.

The way QC works takes a little bit of getting used to. Essentially, a traditional computer works by storing values as a series of bits. Each bit can be set to either 0 or 1. A quantum computer, though, uses quantum bits or qubits. These represent 0, 1 or any superposition of the two. So a computer with one qubit has 2 states, one with 2 qubits has 4 states, 3 qubits gives 8 states, and so on. It doesn’t take long before such a machine becomes massively parallel, able to perform certain tasks unimaginably faster than its classical predecessor.


Quantum Computers' qubits enable a massively parallel approach to problem solving

That’s whether the problem comes in for bitcoin, because certain cryptographic functions rely on the fact that the only way to ‘break’ them without having the password is to brute force them - effectively, trying every input until you find the one that unscrambles the data. Bitcoin relies on cryptographic functions that are, to all intents and purposes, impossible to break using current technology - or any future computer built with known technology. QC could change all that, making it a trivial matter to brute-force a private key.

Bigger fish to fry

This isn’t something that is likely to cause the downfall of bitcoin, though, either now or at any time in the future. There are at least three reasons why.

1) Step-changes like QC don’t happen overnight. Simply, this is still in the realm of science fiction. Though advances are being made, this isn’t a technology that will suddenly mature overnight and emerge as a tool immediately suitable for attacking crypto.

2) Quantum Computing-resistant encryption algorithms exist and are being developed. QC is very good at certain tasks, but not suited to others. There would be plenty of time to upgrade to something QC-resistant, if the need arose (assuming you could gain consensus - a far harder task than developing the required tech…)

3) QC would threaten far more than crypto. A large chunk of what we take for granted in terms of computer security would no longer hold true. Financial transactions of all kinds, email, the integrity of encrypted data on the web, company servers and just about anywhere else would potentially be compromised. Basically, if QC causes the downfall of crypto, you’re looking at an Armageddon scenario for just about everything.

It’s likely that sometime in the next 50 years QC is going to cause some real disruption. That’s why the NSA is working on a new suite of cryptographic algorithms to keep data safe. At least, safe from the bad guys. There’s a good chance they might leave a back door or two in case they want to take a peek themselves.

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