The New Ways to Save Crypto from a Post-Quantum World

What if a key piece of cryptography underpinning bitcoin fell apart?

That might sound like science fiction (or even FUD - fear, uncertainty and doubt) to many a cryptocurrency enthusiast, yet hardly a day goes by without some breakthrough in the field of quantum computing hitting the wires.

And while the technology will have many beneficial effects on humankind, for cryptocurrency holders, the technology could spell devastation.

That's because quantum computers have the ability to unwind much of the cryptography that underlies how data - including cryptocurrency private keys - passes through the internet. As such, researchers in the space are playing it safe, already looking for ways to re-architect cryptocurrency systems to be resistant to quantum computing.

For instance, researchers at last week's Financial Crypto 2018 conference were so concerned about the tech's possible effects on crypto that they're already outlining possible solutions.

"Cryptocurrencies are tightly associated with user's money, and that is an extremely sensitive subject," said Fangguo Zhang, a Sun Yat-sen University researcher and co-author of a new paper, Anonymous Post-Quantum Cryptocash. "As a cryptographer, we have to take precautions on the fast development of quantum computing such that if it becomes strong enough, we are able to update cryptocurrency systems as soon as possible."

That's why Zhang and several others designed a cryptocurrency construction (detailed in the paper) that uses so-called "ideal lattice" cryptography to replace bitcoin's digital signature algorithm so that it could withstand quantum computers.

And although there's disagreement over the timeline quantum computing will be realized, and even over whether it's possible at all, still other researchers are putting their minds to work on a solution.

Saarland University computer science PhD student Tim Ruffing, for example, is working on his own scheme, telling CoinDesk:

"Even if this is still far away, quantum security is already important today."

Replacing digital signatures
And that's because it wouldn't just be one cryptocurrency that would take a hit, but all of them, since the digital signature algorithms would be the vulnerable part of the systems.

These algorithms generate the public/private key pairs that cryptocurrency holders use to store and transfer their bitcoin. While public keys can be shown to other users as they are the mechanism used to receive cryptocurrency, the private key allows users to spend their crypto and as such should be kept, as the name suggests, private.

With computers today, a private key can't be mathematically generated from a public key. But quantum computers could be theoretically so powerful, they could link public and private keys.

As such, much of the research being done looks to replace cryptocurrency's digital algorithms with something else.

For instance, the Zhang's proposal replaces the cryptography with "ideal lattices," which are not only quantum resistant but also bake in privacy features. According to the paper, both unlinkable ring signatures - a technical scheme perhaps most famous because of its use in privacy-oriented cryptocurrency monero - and stealth addresses are added to the scheme.

Although, due to the system's complexity, a whole new cryptocurrency would need to be deployed, and according to Zhang that's not in the researchers' plans, although ome undergraduate students are now testing the system.

Numerous solutions
And since a tremendous amount of money and time is already wrapped up in existing cryptocurrencies, that's not an ideal solution.

As such, other researchers are more focused on re-architecting existing cryptocurrencies to be quantum resistant.

Saarland University's Ruffing is one. Plus, Imperial College London research assistant, Alexei Zamyatin, has also recently co-authored a new paper, although it's not fully finished yet.

Both researchers are independently working on ways to educate users on the problem so that they're ready, since even if new addresses were developed, users would need to take the responsibility to switch to them.

For example, Ruffing posted an idea to a leading bitcoin developer mailing list. Basically, Ruffing describes a "two-step" transaction process, which hides user's public key until the coins are appropriately moved to a quantum-ready address.

Meanwhile, Zamyatin believes another way to push users to securely move their crypto to resistant addresses is through a backwards-compatible soft fork upgrade.

Not only this, but a "huge number" of alternative quantum-resistant signature schemes to a major cryptographic conference last November, according to Zamyatin.

As such, many researchers don't think making cryptocurrency resistant to quantum computers will be that difficult. Instead, several, believe cryptocurrency will be the least of the world's problems in an era ruled by quantum computers.

Zamyatin said:

"We'll have other problems if quantum computers actually come up."