The rise of quantum computing poses a significant threat to the digital signature algorithms that underpin the security of current blockchain systems. The industry acknowledges this risk and is actively adopting post-quantum cryptography (PQC).

This article explores the distinctions between PQC and quantum physics, identifying the projects that are taking serious steps and those merely adopting trendy labels for publicity.

In Brief

Blockchain developers are adapting their cryptographic approaches in anticipation of a new era. While quantum computers capable of breaching Bitcoin's security are not yet available, the crypto sector has begun transitioning to PQC. Some projects are implementing new algorithms, while others are preparing their architectures and migration roadmaps.

Understanding the Threat

The potential for quantum hacking is a legitimate concern. The Shor's algorithm, when executed on a sufficiently powerful quantum computer, can solve the mathematical problems that underpin modern public key cryptography, which secures transactions. While symmetric algorithms and hash functions are resilient against quantum attacks, those based on elliptic curves (ECDSA/EdDSA) remain vulnerable.

This creates a real threat known as HNDL (Harvest Now, Decrypt Later), where attackers collect and store intercepted data in anticipation of future quantum computing capabilities.

PQC encompasses new cryptographic algorithms grounded in mathematical problems that lack efficient quantum solutions (for instance, lattice-based cryptography). Its foundation was established by three standards approved by NIST in August 2024:

  • ML-KEM (key exchange, previously CRYSTALS-Kyber);
  • ML-DSA (digital signatures, previously CRYSTALS-Dilithium);
  • SLH-DSA (hash-based signatures, previously SPHINCS+).

These standards are pivotal for the global shift to quantum-resistant algorithms. A fourth standard, FN-DSA based on FALCON, is nearing completion (FIPS 206).

Some projects were designed with quantum resilience in mind from the outset, such as QRL, which has utilized hash-based signatures since its inception. Algorand integrates the lattice-based Falcon signature in its State Proofs, ensuring quantum-resistant authentication during cross-chain verification.

However, leading cryptocurrencies face a more complex situation. Discussions within the Bitcoin and Ethereum communities are ongoing, and draft roadmaps are being developed. For Bitcoin, two protocol change proposals—BIP-360 and BIP-361—are under consideration.

BIP-360 introduces a new output type called Pay-to-Merkle-Root (P2MR), which, while similar to Taproot, avoids using an internal public key that could be targeted by quantum attacks.

BIP-361 outlines the migration process and a gradual phase-out of Schnorr and ECDSA signatures. The initial phase, projected to occur about three years after activation, aims to prohibit transactions to quantum-vulnerable addresses. Two years later, transactions from such addresses are proposed to be tied to a recovery mechanism that complicates theft via quantum computers.

For Ethereum, the abstraction of accounts is considered a key tool, allowing wallets to transition to post-quantum signature schemes without a hard fork, while an updated strawmap proposes gradual protection measures extending to 2030.

Other notable initiatives include:

  • The Blueshift project has developed and launched the Winternitz Vault on the Solana blockchain, utilizing quantum-resistant one-time signatures for fund storage;
  • Ripple has unveiled a multi-phase plan to prepare the XRP Ledger for the quantum era;
  • Circle is promoting its Arc blockchain as originally designed to withstand quantum attacks;
  • Zcash's strategy includes the implementation of wallets featuring recovery mechanisms post-quantum compromise to safeguard assets and gradually transition the protocol to post-quantum standards.

Important Note: PQC is fundamentally mathematical, involving a shift to new signature algorithms operable on conventional hardware today. QKD (Quantum Key Distribution) focuses on physics, ensuring interception detection through quantum mechanics. Blockchains are addressing their challenges through PQC rather than QKD.

Implications for Readers and the Industry

On one hand, quantum resilience provides a genuine competitive edge for protocols: networks that migrate proactively and effectively mitigate existential risks. On the other hand, the term "quantum-resistant" has become a popular marketing buzzword, often misapplied.

How can one assess claims? By examining specifics:

  1. Does the project utilize standardized NIST algorithms, or is it merely presenting vague notions of "quantum protection"?
  2. Is there open-source code and an audit trail?
  3. Is there a migration plan for existing addresses, or is the focus solely on new ones?

Defending against quantum threats requires meticulous engineering involving dates and standards.

Q-Check ForkLog: Post-Quantum Cryptography

Is there revenue?

Not directly; this represents infrastructural protection rather than a product.

Is it a prototype or a product?

It is a product: NIST standards are finalized, and libraries are accessible.

Is there a roadmap or just a press release?

Serious projects have migration maps, concrete proposals, standards, and open code; marketing-driven ones have loud announcements and slogans.

Who funds it?

Standards are funded by the government (NIST); implementation falls to the protocols and vendors.

What can be checked now?

Open standards and project codes.

What’s Next?

In the next issue, we will transition from mathematics to physics. We will explore quantum internet and QKD, highlighting what physical security protects, what remains vulnerable, where real money lies in quantum communications, and how governments are already getting involved with regulation and contracts.