From Scalpels to Qubits: The Story of the World’s First Post Quantum Blockchain

For more than a decade, Peter Waterland diligently pursued his role as a surgeon. At the same time, he began delving into a variety of intellectual activities (gaining a reputation as a polymath along the way). Among these were cryptography, programming, and blockchain technology. All three propelled him to become a passionate cryptocurrency champion.

Ultimately, Peter’s contributions to the cryptocurrency world included a bitcoin bip38, bitcoin multi-signature wallet, and a bitcoin steganography library.

His writings exhibit this passion as well, as they cover everything from Ethereum economics to private key encryption. The latter topic became his most vexing concern, as he believed it would eventually prove to be the Achilles heel of Bitcoin

Peter realized that a powerful quantum computer could conceivably undermine the Elliptic Curve Digital Signature Algorithm (ECDSA) used in Bitcoin and other cryptocurrencies. Once achieved, an attacker could reconstitute a user’s private key from their public key and access their private funds.

An Idea Is Born

In 2016, the idea of a practical quantum computer seemed like science fiction to many. Quantum computers only existed as a handful of qubits, and IBM was a year away from demonstrating any quantum computing whatsoever.

Peter was convinced that this technology would quickly evolve, however. As he would later assert, “(technological) change comes faster than we expect and often in a non-linear fashion” (The QRL Blog).

Although the threat of quantum computers to the blockchain space appeared distant, several organizations had been preparing for this eventuality.

The first organization to take the quantum threat seriously was PQCRYPTO, a global network of post-quantum cryptographers and related professionals. After ongoing discussions about this threat, the organization recommended XMSS as a post-quantum security solution in March 2015. Several months later, the NSA announced that they were preparing for the quantum threat.

When considering the options, Peter viewed hash-based signature schemes as the best way forward, due to their minimal security assumptions.

Practical Considerations

Shortly afterward, Peter wrote and published the first cryptocurrency whitepaper on the topic, along with the project’s name, the Quantum-Resistant Ledger (QRL). Once security-minded developers began to agree with him, he pulled together a core technical team to make his vision a reality.

On paper, determining the best digital signature solution to the quantum threat appears relatively straightforward. Cryptographers assert that a hash-based digital signature is the simplest and most promising safeguard against quantum computers.

After all, hash-based digital signatures can resist quantum computers because they rely on the one-way nature of a cryptographic hash function. That is, they’re not prone to decryption. These hash functions combine user-fed data with another numerical input to produce a fixed-length digest as output.

Hash functions can be used to create digital signatures only once, however. Peter sought a hash-based signature scheme that could be used repeatedly (to sign a document or conduct a transaction).

The answer was a hash-based signature scheme that employed a ‘Merkle tree’ (binary hash tree). A Merkle tree allows the public keys from many one-time signatures to be concatenated in pairs and hashed upwards in an inverted tree structure to a single root hash.

Ultimately, a hash-based signature scheme named XMSS (eXtended Merkle Signature Scheme) was discovered. XMSS incorporates a Merkle tree and can be used many times over. Peter made it the basis for the Quantum Resistant Ledger (QRL) project, the first post-quantum secure blockchain.

The decision was a critical one since privacy and security are central to Bitcoin’s value proposition. When Bitcoin security appears compromised, its price drops precipitously.

Just this month, FBI agents recovered bitcoin from a wallet belonging to the Colonial Pipeline hackers. Bitcoin quickly lost nearly 10% of its value.

While the on-chain Bitcoin address linked to the Colonial Pipeline ransom wasn’t hacked, the FBI figured out the public key by analyzing on-chain data. When they could link the public key to a particular custodian, they asked the custodian to share the private keys to that address.

A Working Blockchain

As might be expected, the journey from whitepaper to a working blockchain can be ‌arduous. Before achieving mainnet, the technical team must implement a variety of complementary components to the blockchain (such as a multi-signature wallet or a secure messaging protocol for QRL’s p2p network).

In practice, achieving mainnet means moving from an isolated private VPS network connected to a handful of nodes (and under complete developer control) to a public testnet with over 50 nodes spanning the globe.

It also means moving from a handful of Raspberry Pi to high-power Amazon AWS instances.

As might be expected, this move instigated a host of short-term issues that Peter and his team had to resolve (including temporarily moving to a Proof-of-Work consensus). After extensive effort, the QRL core technical team managed to move forward with a mainnet launch in 2018.

In the near term, QRL is working with Geometry Labs to deliver a Proof-of-Stake consensus mechanism, firmly cementing its place in the ranks of second-generation cryptocurrencies.

Geometry Labs is a decentralized finance and cryptography research and development lab. Although relatively small, the lab specializes in helping blockchain outfits refine their Defi products and tooling, blockchain infrastructure, analytics and observatories, and the development of novel cryptographic mechanisms.

Putting Together A Highly-Skilled Team

Along the way, the QRL team has recruited other highly skilled community members to join the project. The ability to do so was critical, as the project was not well-funded (especially in comparison to large projects).

These team members were passionate about the technology. As Peter once noted, “the project’s strength lies in the solid participation of polite, well-informed and helpful community members.”

Since attracting developers was paramount, the project made small but noticeable improvements to quell frustration (such as creating tutorials and updating APIs to facilitate development).

The QRL core technical team also instituted a QRL Improvement Process (QIP) on Github, allowing anyone to suggest improvements to the existing QRL ecosystem. The space encourages safe dialogue between developers and users to occur, such as discussing technical points of view or debating the merits of a particular upgrade.

As the project grew, Peter established a foundation to manage its finances and support development. While foundations are relatively common in the cryptocurrency world, the QRL Foundation has achieved a blockchain with complete post-quantum secure security and crypto-agility.

The QRL project can attribute a large part of its success to its many talented contributors. Although relatively small, the team has made great strides within the past two years.

The project development team is led by its two core developers, Kaushal Kumar Singh and Dr. JP Lomas. Charlie Thompson, James Gordon, and Adem Bilican round out the development team.

Project advocates include Jack Matier (Director of Communications), Michael Strike (Director of Outreach, video personality), and Ryan Malinowski (Director of Advocacy).

Finally, project team advisors include Leon Groot Bruinderink (Ph.D. Post-Quantum cryptography) and Robby Dermody (Co-founder, Counterparty).

Concluding Remarks

As you can see, Peter Waterland devoted a tremendous amount of time and effort to make his vision a reality. Indeed, the project could not have succeeded without him.

In the end, he had more than a great idea. He was able to marry his extensive technical knowledge with team-leadership capabilities.

Today, the QRL project consists of a dedicated team working hard to prepare for a post-quantum future alongside a large and vibrant community.

As the division of labor has expanded, an active group of insiders has stepped up to help lead the team. Known as The QRL Contributors, this informal committee will be expanding its role in project governance.

This transition is both natural and expected, given the organization’s continued growth and complexity. The project’s future is bright, as evidenced by its move to establish a development hub with partners in the United Arab Emirates.

Join the discussion about the future of post-quantum cryptography today in our discord channel at https://discord.gg/WFC3knCT8E