Which Cryptocurrencies Will Survive Quantum Computing

Quantum computers have the potential to break the public-key cryptography that secures nearly every major blockchain today. While practical attacks may still be years away, migrating an entire blockchain ecosystem to new cryptography is a massive undertaking that will likely take years of research, development, auditing, and adoption.

I came across this comparison of post-quantum readiness across major blockchain projects and thought it raised some interesting points.

Some of the article's key takeaways:

• "The threat is shared across chains." Both ECDSA and Ed25519, which between them secure almost the entire market, fall to Shor's algorithm once a capable quantum computer exists.
• "The big names are on roadmaps, not mainnet." Bitcoin, Ethereum, XRP, Cardano, Hedera and Polkadot all have plans, but none has a live, protocol-wide post-quantum signature scheme protecting user accounts today.
• "Only one major chain is quantum resistant today." The Quantum Resistant Ledger has signed every transaction with hash-based cryptography since 2018. Everything else still protects user funds with signature schemes that would be vulnerable to a sufficiently capable quantum computer.
• The article also compares projects with protocol-level implementations against those relying on research, testnets, or opt-in approaches, highlighting why migrating an existing blockchain is a much bigger engineering challenge than simply replacing a signature algorithm.

Whether practical quantum attacks arrive sooner or later is still an open question. Most experts agree it's a matter of when, not if. If migration itself takes years, projects that start late are also likely to finish late.

It will be interesting to see how different blockchain ecosystems execute their migration strategies over the coming years.