Quantum-Safe Blockchains Call for Better Cryptography
The debate is shifting from quantum hardware to post-quantum cryptography, with RLNC and PQC as possible paths for blockchains that need to protect data for years.
Key Takeaways
- Optimum co-founder Muriel Médard says blockchains can become quantum-safe with better cryptography and math that already exists.
- She says harvest now, decrypt later is a risk because encrypted data can be stored for years and still be vulnerable later.
- Médard sees RLNC and post-quantum cryptography as practical routes, while the Ethereum Foundation and Algorand are already working on quantum-safe solutions.
Blockchains do not have to wait for quantum computers to defend themselves against future attacks. According to Optimum co-founder and MIT professor Muriel Médard, the solution is not exotic hardware, but better cryptography and math that already exists. That matters now that more and more sensitive data has to be stored for years and could still be vulnerable to decryption later.
Why This Matters Now
Médard points to a familiar threat: some parties are already collecting encrypted data with the idea of decrypting it later once quantum computing is advanced enough. This is also known as harvest now, decrypt later. For blockchains, that is especially sensitive because they store not just money, but also identity, contracts, and governance.
The broader crypto industry has been looking at post-quantum cryptography for a while. The G7 recently called on organizations to move to PQC to protect sensitive data from future quantum threats. Attention has also grown in the United States after the White House added post-quantum cryptography to its list of critical and emerging technologies. Ripple is also working on a migration path to prepare wallets and transactions for that shift.
RLNC as a Practical Route
The core of Médard’s argument is that you do not have to encrypt everything to become quantum-safe. She points to Random Linear Network Coding, or RLNC, a method where data is split into coded equations that can be mixed along the way and later put back together. According to her, encrypting just a small part of that coded data may be enough to protect the whole thing.
In her view, that makes the approach much lighter than classic PQC solutions, which are often heavier on computing power and network traffic. That point lines up with earlier research on NIST-selected PQC schemes, which found that performance can be acceptable on its own, but larger ciphertexts and signatures can hurt network efficiency, especially when bandwidth or latency is limited.
Médard also points to concrete examples from the industry. The Ethereum Foundation supports research from ZKnox into open-source post-quantum solutions, with the goal of potentially cutting gas fees sharply. Algorand uses FALCON signatures to better protect the entire chain history against quantum threats.
What This Means for Web3
For European crypto and Web3 players, this is more than a technical detail. If blockchains are going to be used more often for financial systems, identity, and governance, then quantum safety becomes a basic requirement instead of a nice-to-have. That means the debate is not just about future hardware, but also about which cryptography is already suitable for systems that need to last for years.
