Migration Playbook: Layer-1 Blockchains
A step-by-step guide to upgrading from ECDSA to post-quantum cryptography. Based on historical upgrades like SegWit, Taproot, and The Merge—expect 5–7 years from proposal to completion.
What This Playbook Covers
Migrating a Layer-1 blockchain to post-quantum cryptography is a multi-year process requiring research, implementation, testing, governance approval, and coordinated user migration. This playbook outlines the complete process, decision points, and lessons learned from projects already attempting migration.
Pre-Migration Assessment
Before starting, evaluate your blockchain’s readiness across four dimensions:
| Dimension | Key Questions | Red Flags |
|---|---|---|
| Technical Capacity | Do you have cryptography expertise on the core team? | No cryptographer, reliance on external consultants only |
| Governance Agility | How long do major upgrades typically take? | Last hard fork took 3+ years or failed entirely |
| Ecosystem Readiness | Are wallets, exchanges, and tooling actively maintained? | Abandoned wallets, single exchange listing |
| Economic Incentives | Will users have reason to migrate? | No fee reduction, no clear benefit to upgrading |
Decision Tree: Is Your Chain Ready?
If you answered “red flag” to two or more dimensions, focus on building capacity before attempting PQC migration. Rushing an unprepared chain risks failed governance, ecosystem fragmentation, or security vulnerabilities from incomplete implementation.
The Five-Phase Migration Process
Each phase builds on the previous. Skipping phases or rushing through them increases risk of failure, security vulnerabilities, or community rejection.
Phase 1: Research & Specification
Objectives
- Choose post-quantum algorithm (ML-DSA/Dilithium recommended by NIST)
- Decide on migration approach (hybrid vs PQC-only)
- Draft technical specification (BIP/EIP/CIP)
- Estimate performance impact and signature size increases
Research Phase Checklist:
- ☐ Review NIST post-quantum standards (FIPS 203 ML-KEM, FIPS 204 ML-DSA, FIPS 205 SLH-DSA)
- ☐ Analyze blockchain-specific constraints (block size, validation time, bandwidth)
- ☐ Benchmark Dilithium/SPHINCS+ performance on your codebase
- ☐ Model signature size impact (transactions per block reduction)
- ☐ Evaluate hybrid vs PQC-only trade-offs
- ☐ Draft 5–7 year migration timeline roadmap
- ☐ Identify “old coins” problem scope (P2PK addresses, dormant wallets)
- ☐ Write formal specification document
- ☐ Publish for community feedback
Lessons from Cardano
What worked: Early research (2018) with Professor Peter Schwabe gave time to explore multiple approaches. Academic peer review built community confidence.
What didn’t: Initial timeline estimates were too optimistic—implementation took 2+ years longer than planned due to complexity.
Lessons from Bitcoin BIP-360
What worked: P2QRH proposal defines clear address format supporting ML-DSA, SLH-DSA, and FALCON. Soft-fork compatible design reduces governance friction.
Challenge: No adoption timeline yet. Community debates ongoing between BIP-360, QRAMP, and P2TRH approaches.
Phase 2: Implementation
Objectives
- Implement PQC signature verification in consensus layer
- Create new address format for PQC keys
- Build wallet support for PQC key generation
- Write comprehensive test suite and deploy to testnet
Implementation Phase Checklist:
- ☐ Integrate Dilithium library (e.g., liboqs, PQClean, or NIST reference)
- ☐ Add PQC signature verification to consensus rules
- ☐ Design new address format (visually distinguishable from legacy)
- ☐ Implement hybrid signature validation (if applicable)
- ☐ Update transaction serialization format
- ☐ Modify wallet key generation to support PQC keys
- ☐ Write unit tests (signature creation, verification, edge cases)
- ☐ Write integration tests (full transaction flow)
- ☐ Perform security audit (third-party cryptographers required)
- ☐ Deploy to internal testnet
- ☐ Fix bugs discovered in testing
- ☐ Deploy to public testnet
Lessons from Ethereum
What worked: Account abstraction (EIP-4337) allows experimentation without hard fork—developers can deploy PQC wallets as smart contracts and test in production.
What didn’t: No single EIP gained consensus yet. Multiple competing proposals (EIP-7932, EIP-7693) created fragmentation and slowed progress.
Lessons from Solana
What worked: Winternitz Vault (January 2025) launched as opt-in solution using hash-based one-time signatures. Users can protect funds without waiting for protocol upgrade.
Limitation: Requires new keys per transaction. Standard wallets remain vulnerable—protocol-level solution still needed.
Phase 3: Governance & Consensus
The Least Predictable Phase
Technical challenges are solvable. Political challenges are not. Bitcoin’s SegWit took years to activate due to miner resistance. Ethereum’s PoS transition required strong leadership to overcome opposition. Budget extra time here.
Objectives
- Present proposal to community stakeholders
- Gather feedback and iterate on specification
- Achieve consensus for hard fork activation
- Coordinate ecosystem (wallets, exchanges, node operators)
Lessons from Bitcoin’s SegWit
What worked: BIP9 version bits allowed miners to signal support, providing clear activation path.
What didn’t: Took 3+ years from proposal (2015) to activation (2017). Miner resistance nearly killed the upgrade. Community fragmented into Bitcoin Cash fork.
Takeaway: Start governance process early. Hard fork is unavoidable for PQC—prepare for potential chain split.
Governance Timeline Reality
Bitcoin: ~22 months for major consensus changes (SegWit, Taproot pattern)
Ethereum: 6–18 months for hard forks with strong foundation support
Polkadot: ~3 months via on-chain governance (fastest major chain)
Centralized chains: Days to weeks (but defeats decentralization purpose)
Phase 4: Activation & Deployment
Objectives
- Deploy code to mainnet (not yet activated)
- Ensure all stakeholders ready (wallets, exchanges, node operators)
- Activate at predetermined block height or date
- Monitor network health post-activation
High-Risk Period: First 48 Hours
The first two days after activation carry elevated risk. Potential issues:
- Chain split: Non-upgraded miners create incompatible fork
- Performance problems: PQC signature verification slower than expected
- Consensus bugs: Edge cases not caught in testing
- User confusion: People send to wrong address type, lose funds
Have rollback plan ready (though hard forks can’t easily roll back).
Lessons from Ethereum’s Merge
What worked: Shadow forks (testing on clones of mainnet) caught bugs before production. Multiple testnets validated approach over 18+ months.
What didn’t: Some staking services weren’t ready—users couldn’t withdraw for months after activation.
Takeaway: Test on multiple testnets. Coordinate with ALL ecosystem players, not just major ones.
QRL: Proof It Can Work
Success case: Quantum Resistant Ledger launched mainnet in 2018 with XMSS hash-based signatures from genesis—no migration required.
Project Zond: EVM-compatible chain with Dilithium signatures now in testnet, proving PQC can work with smart contracts.
Takeaway: PQC blockchain is achievable. The challenge is migrating existing chains, not building new ones.
Phase 5: User Migration
Objectives
- Educate users about need to migrate to PQC addresses
- Provide simple migration tools (one-click wallet upgrades)
- Monitor migration progress across the network
- Set sunset deadline for legacy addresses (optional but recommended)
The “Old Coins” Problem
Coins that never migrate remain vulnerable post-Q-Day. This includes lost keys, deceased holders, and users who simply ignore migration notices. Three controversial options:
| Option | Approach | Trade-off |
|---|---|---|
| Leave Vulnerable | Accept that some coins will be stolen by quantum attacks | Preserves property rights, but creates known attack surface |
| Force Migration | Move old coins to new addresses automatically | Violates immutability principle; who controls new keys? |
| Burn Unmigrated | Make legacy addresses unspendable after deadline | Economically disruptive; reduces supply permanently |
Cardano’s Approach
Sunset deadline after 3–5 years. Unmigrated coins become unspendable but not burned—preserved in case keys are found later. This balances security with property rights.
Lessons from Bitcoin’s P2WPKH Adoption
What worked: SegWit addresses offered lower fees—economic incentive drove voluntary adoption.
What didn’t: Even years later, only ~85% of transactions use SegWit. 15% still use legacy formats with no migration deadline.
Takeaway: Optional migration won’t achieve 100%. Sunset deadline is necessary but will be contentious.
Realistic Timeline Example
Based on historical precedent from major blockchain upgrades:
| Year | Phase | Milestone |
|---|---|---|
| 2025 | Research | BIP/EIP drafted, community discussion begins |
| 2026 | Implementation | Code written, internal testnet deployed |
| 2027 | Governance | Public testnet live, community signaling begins |
| 2028 | Activation | Mainnet hard fork activates, PQC addresses available |
| 2029–2031 | Migration | Users voluntarily migrate to PQC addresses |
| 2032 | Sunset | Legacy ECDSA addresses deprecated (if Q-Day imminent) |
Total time: 7 years from initial proposal to completion. This assumes no major setbacks, governance delays, or technical complications. Add 2–3 years for contentious governance situations.
Cost Estimation
Budget for a complete Layer-1 PQC migration (major blockchain with active ecosystem):
| Category | Cost Range | Notes |
|---|---|---|
| Research & Specification | $50K – $200K | Cryptographer consultation, formal spec writing |
| Core Development | $500K – $2M | Implementation, testing, 2–3 senior devs for 12–18 months |
| Security Audits | $100K – $500K | Multiple audits recommended (consensus + crypto experts) |
| Testnet Infrastructure | $50K – $150K | Cloud costs, monitoring, public testnet operation |
| Ecosystem Coordination | $100K – $300K | Dev rel, documentation, wallet/exchange support |
| Community Education | $50K – $200K | Explainer content, migration guides, user support |
| Total | $850K – $3.35M | For major blockchain; smaller chains less expensive |
Cost Multipliers
This assumes a competent team executing efficiently. Delays, governance disputes, or contentious hard forks can easily double costs. The DAO fork and Bitcoin/Bitcoin Cash split both cost their ecosystems tens of millions in lost productivity and community fragmentation.
Additional Resources
See Who’s Following This Playbook
Track which Layer-1 blockchains are at each phase of quantum migration—and which haven’t started.
Last updated: December 4, 2025 | For project teams: Contact us for guidance on your specific blockchain