Quantum-Resistant Cryptocurrency FAQs: Building Quantum-Safe Crypto
Quantum computers aren't coming. They're already here, just not powerful enough yet to crack your keys. When they are, every blockchain, every wallet, every signed transaction becomes vulnerable overnight.
The good news? We have quantum-resistant algorithms ready. The bad news? Most codebases have no idea where they're using vulnerable cryptography, let alone how to migrate.
Let me walk you through the questions I keep hearing from engineering teams.
When Do We Actually Need to Worry?
The honest answer: nobody knows exactly, but probably sooner than you think.
NIST's timeline suggests quantum computers capable of breaking RSA-2048 could exist by 2030-2035. But "store now, decrypt later" attacks are happening today. Nation-states are harvesting encrypted data right now, banking on future quantum capabilities to crack it.
For cryptocurrency, the threat is more immediate. Your blockchain's transaction history is public. Every signature, every public key. An attacker doesn't need real-time quantum access—they can record everything and crack it later.
Bitcoin addresses that have revealed their public keys (through spending transactions) are vulnerable. Ethereum accounts? Same problem. Most proof-of-stake validators? Exposed.
The migration window is narrower than you think. You need quantum-resistant crypto in production before quantum computers become practical, not after.
What Makes Current Crypto Vulnerable?
Three algorithms power most cryptocurrency systems:
ECDSA (Elliptic Curve Digital Signature Algorithm) - Used by Bitcoin, Ethereum, and most blockchains for transaction signing. Shor's algorithm breaks it completely. A sufficiently powerful quantum computer can derive your private key from your public key in polynomial time.
RSA - Common in key exchange protocols and some legacy wallet systems. Also broken by Shor's algorithm. The math is slightly different but the outcome is the same: complete compromise.
Hash functions (SHA-256, Keccak) - Actually more resistant than people realize. Grover's algorithm only provides quadratic speedup, which means you need to double your key size. SHA-256 effectively becomes SHA-128 security. Not ideal, but not catastrophic.
The real danger? Signature schemes. Your private keys remain safe until you spend coins or sign a transaction. Then your public key becomes visible on-chain, and the countdown starts.
Which Quantum-Resistant Algorithms Should We Use?
NIST standardized four algorithms in 2024 after years of evaluation:
CRYSTALS-Kyber (now ML-KEM) - For key encapsulation. Uses lattice-based cryptography. Fast, small keys, solid security proofs. This is your go-to for key exchange.
CRYSTALS-Dilithium (now ML-DSA) - For digital signatures. Also lattice-based. Larger signatures than ECDSA (2.4KB vs 64 bytes), but fast verification. Most cryptocurrency projects are converging on this.
SPHINCS+ (now SLH-DSA) - Hash-based signatures. More conservative security assumptions, but huge signatures (8-49KB depending on parameters). Good for high-security scenarios where you can tolerate size overhead.
FALCON - Also for signatures. Lattice-based, smaller signatures than Dilithium but more complex implementation. Harder to make constant-time.
My take? Start with Dilithium for signatures unless you have specific requirements pushing you elsewhere. The signature size is manageable, the performance is good, and it has the widest adoption momentum.
How Do We Migrate Without Breaking Everything?
This is where it gets tricky. You can't just swap algorithms and redeploy.
Hybrid schemes are the current best practice. Use both classical and quantum-resistant algorithms during transition. A transaction is valid only if both signatures verify. This protects against both current attacks and future quantum attacks.
Transition period - Support both, encourage PQC adoption
Deprecation - Eventually remove classical crypto (years away)
The audit phase is where most teams get stuck. Finding every ECDSA call, every key derivation function, every place you're verifying signatures—it's not just in your core protocol. It's in your wallet code, your RPC layer, your testing infrastructure, your deployment scripts.
This is where Glue becomes valuable. Instead of grepping for "ecdsa" and hoping you caught everything, Glue indexes your entire codebase and can trace every cryptographic dependency. Where are you calling secp256k1? Which modules depend on it? What's the blast radius of changing that signature scheme?
What About Performance?
Quantum-resistant crypto is slower and bigger. No way around it.
Dilithium signatures verify quickly (comparable to ECDSA), but generation is 5-10x slower. Signatures are 40x larger. For a blockchain processing thousands of transactions per second, this matters.
Verification speed matters more than signing for blockchain consensus. Validators need to verify every transaction. Dilithium holds up reasonably well here.
Signature size is the bigger issue. A 40x increase means blocks get bigger, bandwidth requirements increase, and storage costs rise. You'll need to compress, batch, or aggregate signatures to keep this manageable.
Can We Aggregate Post-Quantum Signatures?
This is an active research area. Classical BLS signatures (used in Ethereum 2.0) have beautiful aggregation properties—you can combine thousands of signatures into a single small signature. We don't have equivalent PQC schemes yet.
Some promising directions:
Hash-based aggregation - SPHINCS+ signatures can be partially aggregated through Merkle tree manipulation, but savings are limited.
Lattice-based tricks - Research into aggregatable lattice signatures is ongoing. Nothing production-ready.
Threshold schemes - You can do threshold signatures with lattice crypto, which helps with multi-sig scenarios.
For now, plan on larger data structures. If you're building new protocols, design with this in mind from day one. Older protocols will need more creative solutions.
What's the Migration Risk?
Every cryptographic migration carries risk. You're touching the most security-critical code in your system.
The common failure modes:
Incomplete migration - You switch your signing code but miss key derivation. Or you update the protocol but forget about archived transactions.
Implementation bugs - PQC libraries are newer and less battle-tested. liboqs is solid, but edge cases exist.
Side-channel attacks - Lattice-based crypto is vulnerable to timing attacks if implemented carelessly. You need constant-time implementations.
Protocol-level issues - Your blockchain's consensus mechanism might make assumptions about signature size or verification time.
Testing is harder than with classical crypto because the edge cases are different. Your existing test suite won't catch PQC-specific bugs.
Glue's code health mapping helps here too. You can see which cryptographic modules have high churn (frequent changes = higher bug risk), which teams own them, and where complexity clusters. Migrating high-complexity, high-churn modules to PQC? That needs extra scrutiny and experienced reviewers.
Should We Wait for Better Algorithms?
No. Use what NIST standardized now.
Yes, research continues. Yes, we might find more efficient schemes. But waiting is worse than migrating now with hybrid schemes. You can always add new algorithms later.
The crypto community spent eight years evaluating NIST's PQC candidates. They're conservative choices. Lattice problems have been studied for decades. We won't discover Dilithium is completely broken next year.
What might happen? We might find small optimizations, better parameters, or complementary schemes. That's fine. Hybrid deployments give you flexibility.
How Do We Track All This?
Manual tracking doesn't scale. Spreadsheets of dependencies become stale. Architecture diagrams lie.
You need automated visibility into where cryptography lives in your codebase. Not just the obvious places like your consensus layer, but:
Key derivation in wallet libraries
Signature verification in RPC handlers
Hash functions in Merkle tree implementations
Random number generation in nonce selection
Cryptographic primitives in smart contracts (if applicable)
When I worked on a cryptocurrency protocol migration last year, we found ECDSA calls in 47 different files across 12 repositories. Only 30% were in the "crypto" module. The rest were scattered through tests, utilities, examples, and vendor dependencies.
Glue mapped the dependency graph automatically. We could see exactly which functions called cryptographic primitives, trace the call chains, and identify which teams needed to coordinate on the migration. What would have taken weeks of manual analysis happened in minutes.
What About Governance?
Technical migration is only half the problem. Cryptocurrency protocols have decentralized governance.
You need:
Community consensus on migration timeline
Clear communication about risks and benefits
Coordination across wallet developers, exchanges, node operators
Hard fork planning (for blockchains requiring protocol changes)
Education materials for end users
Start these discussions now. Governance moves slowly in decentralized systems. You want consensus before quantum computers become a threat, not after.
The Bottom Line
Quantum-resistant cryptocurrency isn't a nice-to-have anymore. It's infrastructure work you need to start planning today.
Use hybrid schemes with Dilithium. Map your cryptographic dependencies completely. Test thoroughly. Plan your migration timeline in years, not months.
The teams that start now will migrate smoothly. The ones that wait will rush, make mistakes, and compromise security when quantum computers arrive.
Your codebase is more complex than you think. Your cryptographic surface area is larger than you realize. Find out now, before it becomes a crisis.
