Will Quantum Computers Break Bitcoin?
Tags: Cryptocurrency, Bitcoin, Encryption, Blockchain, Quantum Computing

In September of this year, Google made headlines when they announced that they had achieved “Quantum Supremacy”. They had reached a major milestone in the development of quantum computing- solving a problem that is essentially impossible for classical computers to perform. This has rekindled interest in the potential threat that quantum computers could theoretically pose to bitcoin and other cryptocurrencies. If quantum computers can smash through some of the most advanced cryptography on earth, could they one day “break” blockchains as well?

Before we go any further- what IS a quantum computer?

Classical computers like the one you’re reading this on right now use binary code- everything that it does- email, word processing, youtube videos, you name it- can be broken into electrical and optical pulses representing 1s or 0s. Everything from a smartphone to a laptop to Summit, the world’s most powerful supercomputer owned by the US Department of Energy- are considered classical computers.

Quantum computers work in a completely different way. Instead of using “bits” represented 1s or 0s, they use quantum bits or quibits, subatomic particles which can be 1s, 0s, or both at the same time.

IBM’s 50-quibit quantum computer (Image source: Engadget)

We don’t need to get too caught up in the details of quantum mechanics, but here’s what you need to know: quantum computers have calculating power that vastly surpasses even the most powerful classical computers.

Google’s “Sycamore” quantum computer was able to crack in just over 3 minutes a mathematical problem that would have taken the previously mentioned Summit 10,000 years to solve.

So, why is this dangerous for bitcoin?

Blockchains, including the one that bitcoin runs on, make use of extremely advanced encryption which results in permanent, immutable records. The encryption is so strong that there is simply no way anyone using a classical computer can break it.

When you hear about cryptocurrencies being “hacked” what actually happened is someone found a vulnerability in a faulty smart contract (i.e. “The DAO”) or and private keys being stolen. It does NOT mean that that the underlying blockchain tech itself was hacked, because that’s not possible.

A quantum computer however could theoretically smash right through all modern forms of encryption, including that used by bitcoin. This means a criminal armed with a quantum device could break private keys, steal cryptocurrency and wreak all kinds of havoc.

Imagine for example, if this criminal hacked the private keys to Satoshi Nakamoto’s wallet, which holds over 1 million BTC, and began selling them off rapidly. More people would begin to sell in a panic, and the entire crypto market could crash.

How likely is a quantum attack on bitcoin?

Right now? It’s pretty unlikely. While quantum computers are impressive they are also extremely expensive and difficult to build. They are also really not practical for anything besides advanced calculations, and they can only be found in R&D centers of corporations, universities and government agencies. It is estimated that we are approximately 5–10 years away from a quantum computer powerful enough to smash bitcoin’s level of encryption.

While the threat may not be imminent, does this mean that blockchains are obsolete, and bitcoin is doomed?

Not so fast. The advancement of quantum computing means that encryption in general will have to evolve, and that includes all technologies that make use of encryption, like blockchains. Several projects such as “Quantum Resistant Ledger” (QRL) are being designed by teams working on preemptive solutions to quantum attacks.

It’s possible that bitcoin and other cryptocurrencies will have to adopt more advanced, “quantum proof” blockchains in the future.

While the quantum computing threat should not be keeping crypto enthusiasts up at night, it is something worth keeping an eye on in the medium to long term.

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