XRP Ledger switches to quantum-resistant signatures, with a 2,420-byte proof replacing elliptic curve

XRP Ledger (XRPL) is closing out the year with a series of notable technological upgrades, after a period of increased adoption and many important development milestones.

On December 24th, Denis Angell, senior software engineer at XRPL Labs, announced that AlphaNet – a public test network for developers – has been integrated with “post-quantum” cryptography along with native smart contracts (native smart contract).

“Q-Day” and the inevitable threat from quantum computers

Most current blockchains, including Bitcoin and Ethereum, protect user assets with elliptic curve cryptography (ECC).

This model is secure because, with traditional computers, reversing a public key to find the private key is nearly impossible. However, this entire assumption is based on the limits of classical physics.

Quantum computers operate on a different principle, using qubits to process many states simultaneously. Experts predict that, once they reach sufficient power and run Shor’s algorithm, quantum computers could break ECC in just a few seconds. This point in time is called “Q-Day” by security agencies.

The AlphaNet update is designed to directly address this risk. Angell confirmed that the network is now operating with CRYSTALS-Dilithium.

Notably, the US National Institute of Standards and Technology (NIST) recently standardized this algorithm – now called ML-DSA – as a primary defense layer against quantum attacks.

Integrating Dilithium into the testnet helps XRPL Labs “vaccinate” the ledger, preparing it for future hardware breakthroughs.

Anatomy of the post-quantum upgrade

According to Angell, this change impacts the entire core structure of XRPL. AlphaNet has been redesigned with new components: Quantum Accounts, Quantum Transactions, and Quantum Consensus.

Quantum Accounts change how users establish identity. On the old network, the relationship between private keys and public keys was based on elliptic curves. On the upgraded AlphaNet, this relationship is based on lattice mathematics.

Users create Dilithium key pairs, forming a complex mathematical structure that makes it impossible for both traditional and quantum computers to reverse-engineer the private key, even with complete quantum hardware.

Quantum Transactions secure the flow of assets. Every XRP or other token transaction must be signed with a digital signature. The new protocol requires this signature to use Dilithium, ensuring no system can forge user approval.

Quantum Consensus takes on the role of protecting the network’s “truth.” Validators – the servers that agree on transaction order – must also use the new cryptographic mechanism.

If validators continue to use weak cryptography, quantum attackers could impersonate validators, seize voting rights, and rewrite ledger history. The upgrade forces all validator nodes to communicate through quantum-safe channels.

The technical cost of quantum resistance

While offering long-term security benefits, switching to Dilithium also entails significant operational costs.

Dilithium signatures are much larger than ECDSA signatures. An ECDSA signature is only 64 bytes, whereas a Dilithium signature requires about 2,420 bytes.

This directly impacts network performance. Validators must transmit larger data blocks, consuming more bandwidth and increasing latency. The size of the ledger history also grows rapidly, leading to higher storage costs for nodes.

AlphaNet is deployed as a testing environment to gather data on these trade-offs. The engineering team will evaluate whether the blockchain can maintain transaction throughput under increased data loads.

If the ledger becomes too bulky, barriers to participation for independent validators will rise, raising concerns about network centralization.

Narrowing the programming gap

Beyond security, the update also addresses a long-standing competitive weakness of XRPL.

For many years, XRPL handled payments efficiently but lacked programming capabilities, making it difficult to attract developers and liquidity like Ethereum or Solana.

Smart contracts have fueled the explosive growth of these ecosystems, enabling markets, lending protocols, and automated trading to operate directly on-chain. As a result, Ethereum and Solana have become the two largest DeFi platforms, with total value locked exceeding $100 billion.

Previously, XRPL lacked this capability, so its activities mainly revolved around transfers.

Native smart contracts on AlphaNet are changing this landscape. They allow developers to build directly on the base layer, without needing sidechains or external frameworks.

These smart contracts leverage existing XRPL features such as AMM, decentralized exchanges, and escrow mechanisms, opening up space for developing DeFi services far beyond simple payments.

This helps XRPL explore new directions, lowers barriers for teams familiar with smart contract languages, and enables the network to compete based on on-chain activity volume rather than just payment flows.