Post Quantum Migration and the Path to Resilient Blockchains

In our last post, Managing the Quantum Threat to Blockchains, we outlined why quantum computing poses a long term risk to today’s cryptography. 

Here, Citi Institute’s Ronit Ghose continues the conversation with Thomas Coratger, Lead of the Post Quantum Team at the Ethereum Foundation. They discuss how a practical migration could unfold, what timelines are realistic and how responsibilities might be divided up.  

How are quantum resilient solutions likely to be implemented, and who is responsible for what?

The move to quantum safe cryptography will be a layered, multi year transition. 

At the protocol level, developers need to provide the foundations that let the network support post quantum options without introducing instability. Their job is to create the rails so everything else can migrate gradually and safely.

Wallets and applications will carry much of the user facing work. Most people only interact with the blockchain through a wallet, so this layer must make key updates and new authentication flows simple and understandable. 

Validators and infrastructure operators – who secure the network’s consensus and often safeguard large value pools – must upgrade their signing systems, hardware and operational processes early on. They tend to have higher security stakes and stricter procedural requirements.

And finally, users will eventually need to migrate their accounts and keys. The aim, though, is to make this feel like a normal software update rather than a technical chore.

A successful transition depends on all these layers working together: the protocol provides capability, infrastructure keeps things secure, wallets smooth the transition and users complete the loop. 

What is Ethereum already doing to prepare for quantum resilience?

Lots of work. Quantum readiness is now treated as a full scale engineering effort. The Ethereum Foundation has a dedicated post quantum team focused on research, migration planning and ecosystem coordination.

On the consensus side, a major area of work is making sure the network can handle larger, heavier post quantum signatures without compromising decentralisation. 

Researchers are also evaluating different post quantum signature options and funding work to strengthen implementation quality and testing frameworks.

At the execution layer, new proposals would allow smart contracts to verify post quantum signatures. This means developers could start experimenting with quantum safe authentication before the protocol itself fully transitions.

And beyond the technical work, a big focus is ecosystem alignment.  Much of the preparation essentially comes down to getting everyone ready well before quantum attacks become realistic.

How does quantum resilience influence Ethereum’s evolving architecture?

It’s increasingly becoming part of core thinking about the road ahead.

A central theme is cryptographic agility – designing the system so it is flexible enough to swap in new cryptography without forcing users or validators to rebuild their digital lives.

One example is the push toward account abstraction, which separates a user’s identity from a fixed signature scheme. This could allow people to switch to quantum safe signatures in the future without changing their addresses or moving assets.

On the consensus side, proposals are assessed partly on whether they can support heavier crypto without undermining decentralisation. Anything that adds burden to validators is examined through a “post quantum readiness” lens.

Modularity also plays a role. By keeping execution, consensus and data availability more independent, one layer’s cryptography can be upgraded without re architecting the entire system.

And more broadly, long term preparedness should be built in: developing upgrade paths, testing tools and fallback mechanisms now so the network can react calmly even if quantum timelines accelerate.

What economic trade offs would come with migrating to post quantum cryptography?

There are some unavoidable costs, but they can be managed.

The main challenges stem from quantum safe signatures being larger and more intensive from a computational standpoint. 

Teams are exploring aggregation, specialised verification shortcuts and off chain processing to keep the impact minimal.

On the validator side, larger cryptographic objects could increase bandwidth and storage needs. If handled poorly, this could raise barriers to participation. That’s why there’s active work on more efficient proof systems and aggregation techniques to keep hardware requirements modest.

But this transition also presents an opportunity: Ethereum could use the move to post-quantum cryptography (PQC) to simplify and modernize parts of its protocol, potentially improving efficiency and decentralization in the long run.

The goal is to strengthen security without making the network slower or more expensive—and early preparation makes that possible.

How important is cross chain coordination?

Coordination is important, but full standardization across chains is unlikely.

Where coordination matters most is at the interfaces: bridges, custodians, wallets, and cross chain messaging systems. These components often operate across multiple ecosystems, and mismatched post quantum approaches could create bottlenecks or security gaps.

Shared standards for things like signature formats or key management practices would make life easier for developers and auditors and reduce migration friction across the industry.

But each blockchain has its own architecture, governance, and performance constraints. They will inevitably make different choices and move at different speeds.

A practical approach is to coordinate where interoperability matters and allow more independent evolution where it doesn’t.

How long could a realistic migration take?

For major blockchains, a five to seven year timeline is realistic—mostly because coordination takes time.

The process begins with research, testing, and audits, which can take several years. Then comes a gradual adoption phase, where users, validators and applications migrate at different speeds. In decentralized systems, upgrades can’t be forced.
The final phase is consolidation, where the network makes quantum safe options the default and eventually retires older cryptography.

It's not the coding that takes longest – it’s moving millions of users and thousands of operators safely and smoothly.

What are the main barriers to deploying post quantum cryptography today?
Mostly practical ones. Existing blockchains were built around small, efficient elliptic curve signatures, while quantum safe options tend to be bigger and heavier.

The biggest obstacles are:

• larger signature sizes
• slower verification
• more demanding storage and bandwidth requirements
• lack of mature aggregation methods
• the need for careful implementation and audits

But research is tackling each of these—through compression, new proof systems, specialised verification tools and high assurance cryptographic libraries.
The aim is for the shift to feel seamless for users, with the network handling most of the complexity behind the scenes.