Ethereum has begun preparing for the quantum threat

There is currently no quantum computer capable of hacking Ethereum. But the network's developers are already operating on the assumption that one might eventually emerge.

This is a fundamental problem. The security of Ethereum, like that of most modern blockchains, relies on cryptography developed in an era when sufficiently powerful quantum computers did not exist. In particular, elliptic curve digital signatures are potentially vulnerable to Shor’s algorithm: if a sufficiently powerful and stable quantum computer were to emerge, some of the cryptographic assumptions that currently protect accounts and validators would cease to function.

You can't wait for this moment.

Migrating a global network that holds hundreds of billions of dollars in assets to a new cryptographic system is not an update that can be rolled out in a matter of weeks. New algorithms must be created, tested, subjected to attacks, optimized, and integrated into clients—and only then can the infrastructure be gradually migrated to them.

That is why Ethereum is already preparing for a world in which current cryptography may not be sufficient.

And it was precisely in the course of this work that a rather unexpected turn of events occurred.

On August 13, Ethereum Foundation researcher Justin Drake announced, “Goodbye, Poseidon!”

Ethereum is abandoning a cryptographic research area that it has been exploring for about eight years and on which, according to Drake, eight-figure sums were spent.

It may be replaced by technologies that are already decades old.

What Ethereum Is Trying to Protect

The quantum threat to blockchain is often described in overly simplistic terms: “A quantum computer will be able to hack Ethereum.”

In practice, this does not mean the immediate collapse of the entire network.

One of the key issues is digital signatures.

An Ethereum user verifies their right to manage assets using a private key. Validators also use cryptographic signatures to participate in the consensus process.

Today, the security of these mechanisms is based on mathematical problems that are practically impossible to solve using existing classical computers within a reasonable amount of time.

Quantum computing challenges this assumption.

Shore's algorithm theoretically allows a quantum computer to efficiently solve the problems underlying elliptic curve cryptography. If a machine of sufficient scale is ever built, existing signature schemes will be at risk.

And the Ethereum Foundation is already treating post-quantum security as a separate strategic area of focus for the network's development.

In January 2026, the Foundation publicly announced that it was stepping up its efforts on quantum resilience. Today, new signature schemes and proof infrastructure are being developed in this area, and more than ten client teams are participating in interoperability tests.

In other words, this is no longer just a theoretical discussion.

Ethereum is gradually building the architecture that should enable the network to transition to quantum-resistant cryptography before such a migration becomes urgent.

And that's when Poseidon appears

To understand what happened on August 13, we need to go back about eight years.

Ethereum has been moving more and more toward zero-knowledge proofs—cryptographic proofs that allow one to verify the correctness of a computation without having to repeat the entire computation oneself.

But a technical problem arose.

Traditional hash functions like SHA work perfectly well on standard processors, but using them within certain proof systems was expensive.

So cryptographers took a different approach: they began developing special SNARK-friendly hash functions.

One of them was Poseidon.

Its design was specifically optimized for the arithmetic used within zero-knowledge proof systems. As a result, operations that were computationally expensive for conventional SHA-like functions could be proven much more efficiently.

For Ethereum, this looked like a potential part of its future cryptographic stack.

A long-term research project has begun.

Eight years and an eight-digit sum

According to Justin Drake, research in this area took about eight years, and the Ethereum Foundation's total expenditures reached an eight-figure sum.

In other words, we're talking about at least tens of millions of dollars in research investments in the broader field of cryptography and proofs, of which Poseidon was a part.

In fact, Ethereum didn't just fund the development.

Foundation tried to test the structural safety as aggressively as possible.

The researchers were paid to perform a cryptanalysis of Poseidon, identify potential attacks, and verify its mathematical assumptions.

And in early 2026, the Ethereum Foundation went even further.

The Poseidon Prize, with a prize pool of nearly $1 million, has been launched.

The challenge was unusual: essentially, Ethereum was offering researchers money to try to break the cryptography that the network itself was considering for future use.

The competition was supposed to last several years.

But it didn't last.

On August 1, everything came to a halt

On August 1, 2026, the Poseidon1 Collision Prize was suspended.

And just twelve days later, Justin Drake announced:

"Goodbye, Poseidon!"

After eight years of research, the Ethereum Foundation has decided not to use Poseidon in its future L1 architecture.

At first glance, a clear suspicion arises: a critical vulnerability has been found in the algorithm.

However, there is no public confirmation of this.

Poseidon has not been reported as having been hacked, and existing projects currently using it have not been instructed to cease operations immediately.

The reason turned out to be something else.

While Ethereum was refining its specialized cryptography, the technology behind proofs themselves has evolved.

Ethereum has decided to revert to its old cryptography

In recent years, new proof systems have emerged that are capable of handling standard binary computations much more efficiently.

The development of binary-field SNARKs has become particularly important.

It was right here that Ethereum's initial calculations changed.

Previously, SHA was not well-suited for SNARKs, which is why Poseidon was developed.

It is now possible to construct a SNARK that no longer requires a special hash.

Drake summed up this turnaround in a single sentence:

Instead of SNARK-friendly hashes, we now have hash-friendly SNARKs.

And that completely changes the choice of technology.

Since standard SHA or BLAKE functions can be used quite effectively within modern proof systems, the need to take on the additional risk associated with a new, specialized hash function is greatly reduced.

Ethereum may use cryptographic primitives that researchers have been studying and attacking for decades.

That is precisely why the future L1 architecture is now considering SHA or BLAKE instead of Poseidon.

Why is this important, especially as we approach the quantum era?

Here, the story comes full circle, returning to where it all began.

Preparing Ethereum for quantum computers will require replacing more than one function.

Networks may need to change their signature schemes, state verification methods, proof architecture, and some basic cryptographic primitives.

The more experimental cryptography a system contains, the more assumptions must be considered secure.

Therefore, the ability to use long-established and much better-understood functions becomes an advantage.

Ethereum is essentially trying to reduce the number of unknowns ahead of one of the largest potential migrations in blockchain history.

Work is already underway on components such as leanVM, leanXMSS, and leanSig, which are being considered in the context of Ethereum’s future post-quantum architecture.

But that doesn't mean Ethereum will become quantum-resistant tomorrow.

And it certainly does not mean that today's network is already under attack from quantum computers.

The meaning of what is happening is exactly the opposite:

Ethereum is trying to complete the migration before the threat becomes a reality.

What's Next

The next step is much more difficult than choosing between Poseidon and SHA.

Ethereum must ensure that post-quantum cryptography is not only mathematically secure but also practically viable for a global blockchain.

New signatures may be larger. Verification may require additional computations. Proofs must be generated quickly enough. Clients from different developers must process the new cryptography in the same way.

After that, there is still one more issue to address—the migration of users and validators.

Ethereum cannot simply be switched over to a completely new key system overnight.

That is why the current effort is focused on preparing the infrastructure that will enable a gradual transition.

And that is precisely why the decisions being made right now may turn out to be more important than the brief message “Goodbye, Poseidon” suggests.

Conclusion KLJO

The quantum threat seems distant today precisely because there is not yet a computer capable of attacking Ethereum. But for a network of this scale, the moment it appears will already be too late to start preparing.

Ethereum is essentially trying to buy some time right now: to test new approaches, eliminate unnecessary cryptographic risks, and prepare the infrastructure for the transition before it becomes necessary.

The case of Poseidon is particularly telling here. Eight years of research and millions of dollars weren't enough to justify sticking with the technology once a more reliable alternative emerged.

And the main question now is not whether sufficiently powerful quantum computers will be developed.

The main question is whether Ethereum will be able to update its security measures before they appear.