I still remember the first time someone explained Poseidon to me over coffee a few years back. The pitch sounded almost too good: a hash function built from the ground up for zero-knowledge proofs, lighter inside SNARKs, and supposedly the future of efficient cryptography on Ethereum. Fast forward to this week and the same researcher who once championed that vision just declared the whole effort over. Ethereum’s layer-1 roadmap is walking away from Poseidon after what has been described as an eight-year, eight-figure research rabbit hole. The network is pivoting toward familiar, battle-tested hashes like SHA-2 and BLAKE2s instead.
That single announcement carries more weight than most protocol updates. It is not simply a technical swap. It signals a deeper shift in how Ethereum thinks about long-term security, quantum threats, and the practical trade-offs of specialized cryptography. In my view, this is one of those quiet decisions that will shape the chain for the next decade.
Why Ethereum Is Leaving Poseidon Behind
Poseidon arrived in 2019 as a purpose-built tool for SNARK-friendly hashing. Traditional functions such as SHA-256 rely on binary operations that used to be expensive to prove inside zero-knowledge systems. Poseidon was designed around algebraic structures that played nicer with the prime fields most early SNARKs preferred. For a while the approach looked like a clear win. Rollups, zkVMs, and various privacy tools adopted it widely. Billions of dollars in value now sit behind systems that still rely on it.
Yet the Ethereum Foundation has decided that layer 1 itself will not follow that path. Researcher Justin Drake framed the decision as the natural conclusion of years of work. The key insight, he noted, was not the invention of ever more SNARK-friendly hashes. It was the arrival of hash-friendly SNARKs—proof systems that can handle ordinary binary hashes at practical speeds.
In hindsight the key was not SNARK-friendly hashes, but hash-friendly SNARKs.
That single sentence captures the pivot. Once binary-field SNARKs became efficient enough, the original performance advantage of Poseidon largely disappeared. Researchers can now prove roughly one million traditional hash calls per second on a laptop, with only about a hundred-fold overhead compared with native CPU execution. Suddenly the specialized function no longer looked essential for the base layer.
The Rise of Binary-Field Proof Systems
Earlier SNARK designs lived mostly in large prime fields. Representing simple bit operations such as XOR inside those fields was costly. Binary fields flip that relationship. Working over the smallest prime—two—lets the proof system speak the same language as ordinary computers. Boolean logic and standard hash functions become natural rather than forced.
Projects exploring this direction, including Binius and Flock, have pushed the numbers higher still. One open research effort that uses AI to optimize proving code recently hit 1.8 million BLAKE3 compressions per second. That represents a more than twofold improvement over its own earlier baseline. These gains matter because they let Ethereum keep using hashes that already enjoy decades of public scrutiny instead of relying on a relatively young construction that still needs continuous cryptanalysis.
I find this philosophical shift almost as interesting as the technical one. For years the community treated SNARK efficiency as the primary design constraint and tried to invent cryptography that fit inside it. Now the constraint is loosening, and researchers can prioritize long-term confidence and simplicity instead. That feels healthier.
What This Means for Existing Poseidon Users
It is important to be clear about scope. The decision applies to Ethereum’s own layer-1 roadmap. Existing rollups, applications, and virtual machines that already use Poseidon are under no obligation to abandon it tomorrow. Many of them will continue running the function for years. The Foundation is simply saying that the base protocol itself will not depend on it going forward.
That distinction matters. Specialized hashes still offer advantages in certain constrained environments. Nothing prevents a rollup team from keeping Poseidon if the performance profile continues to suit their needs. The L1 choice is about maximizing security assumptions that have already survived extensive independent review.
Post-Quantum Pressure Is Accelerating Everything
The Poseidon decision sits inside a larger conversation about quantum resistance. Ethereum currently relies on elliptic-curve cryptography for accounts, parts of consensus, and data availability. A sufficiently powerful quantum computer would threaten those primitives. Preparing for that eventuality has moved higher on the priority list.
Recent progress in AI-assisted cryptanalysis has complicated some of the more exotic post-quantum candidates. Lattice-based and isogeny-based designs have encountered setbacks that make simpler alternatives look more attractive. Hash-based signatures sit near the top of that list. They rest on relatively well-understood assumptions, even if the individual signatures tend to be large.
Size is the classic objection. A single hash-based signature can be too bulky for comfortable on-chain use at current gas prices and block limits. SNARK aggregation offers a practical workaround. A proof system can verify hundreds or thousands of those signatures off-chain and then post a compact proof that the network accepts. The same technique works for multisignature schemes and threshold arrangements. Authorization rules live inside the proof rather than as raw signature data on every transaction.
Wallet-level experiments are already underway. One optimized SPHINCS-based verifier demonstrated account protection at roughly 127,000 gas with a signature size around 3.7 kilobytes. At the time the verification cost translated to only a few cents. Numbers like that make the approach feel less theoretical and more like an engineering problem that can be solved.
LeanVM and the 2027–2028 Timeline
The practical vehicle for much of this work is leanVM, a minimal zero-knowledge virtual machine aimed at verifying and aggregating cryptographic proofs. The current schedule targets a production-grade version in 2027. Broader deployments across consensus, data, and execution layers are penciled in for 2028. Those dates live inside the Strawmap coordination document that stretches through 2029; they are planning targets rather than fixed activation dates.
Each layer will receive the technology independently. Consensus, data availability, and execution all have different constraints, so the same underlying proof machinery will be adapted rather than dropped in as a single upgrade. Independent client teams will still need to implement, test, and coordinate every change. That process is never instantaneous, but the direction is now clearer than it was a year ago.
I have followed enough Ethereum roadmaps to know that timelines slip. Still, the combination of concrete performance numbers, a named virtual machine, and explicit layer-by-layer plans gives this effort more substance than many earlier post-quantum discussions.
Why Established Hashes Matter for Long-Term Confidence
SHA-2 and BLAKE families have been studied for years outside any zero-knowledge context. Cryptographers, standards bodies, and hostile researchers have all taken turns attacking them. That shared history is valuable. A brand-new construction, no matter how elegant, always carries residual uncertainty until it has survived similar scrutiny.
By choosing functions that already possess long public track records, Ethereum reduces the surface area that needs specialized analysis. The remaining work—embedding those hashes correctly inside binary-field SNARKs, auditing the circuits, measuring real-world performance—remains substantial. Yet it is a different and arguably more manageable kind of work.
There is also a cultural dimension. Specialized cryptography can sometimes feel like a private conversation among a small group of experts. Using widely understood primitives keeps more of the security story accessible to a broader set of reviewers and client implementers. That openness has always been one of Ethereum’s strengths.
Practical Implications for Users and Builders
For ordinary users the change will be invisible for a long time. Account abstraction, smart wallets, and existing applications continue as before. The benefits appear gradually as the protocol itself becomes more resilient to future cryptographic threats.
Builders face a clearer set of signals. If you are designing systems that will live for many years, aligning with the hashes and proof systems the L1 intends to use reduces future migration friction. Teams that already invested heavily in Poseidon still have options; the ecosystem is large enough to support multiple approaches. The base layer simply will not mandate the specialized path.
Investors and institutions watching regulatory developments will notice another angle. Standards bodies have already published their first post-quantum recommendations and are urging early migration planning. Ethereum’s emphasis on aggregation and compact proofs aims to keep the on-chain footprint manageable even while signatures grow larger. That focus on practicality rather than pure theoretical security is likely to matter when real systems start upgrading.
- Layer-1 will favor hashes with long public cryptanalysis histories
- Binary-field SNARKs make ordinary hashes competitive inside proofs
- Hash-based signatures become more practical through aggregation
- leanVM is scheduled for production readiness in 2027
- Layer deployments are targeted for 2028 across consensus, data, and execution
The Broader Philosophical Shift
Perhaps the most interesting part of this story is how research priorities evolved. For nearly a decade the dominant question was “How do we make cryptography cheaper inside SNARKs?” The answer, for a while, was to invent new hashes optimized for that environment. The newer question is almost the reverse: “How do we make SNARKs powerful enough to handle the cryptography we already trust?”
That inversion feels healthy. It prioritizes security assumptions that have already been stress-tested in the open rather than relying on the hope that a specialized design will remain unbroken. It also keeps Ethereum closer to the broader cryptographic community instead of creating an isolated island of SNARK-specific primitives.
I have watched enough protocol debates to know that no decision is ever final. New proof systems will appear. Performance numbers will improve further. Someone may yet invent a specialized hash that combines the best of both worlds. For now, though, the Foundation has chosen the path that maximizes existing confidence while still delivering the performance required for a lean, scalable L1.
Looking Ahead to a Quantum-Resistant Ethereum
Quantum computers capable of breaking current elliptic-curve systems remain years away by most estimates. That buffer is useful, but it is not infinite. Migrating an entire ecosystem of wallets, exchanges, contracts, and infrastructure takes time. Starting the research and engineering now is the only responsible approach.
Hash-based signatures plus SNARK aggregation form one concrete path. Other post-quantum families will continue to be evaluated. The important point is that Ethereum is no longer treating quantum resistance as a distant research topic. It has become part of the active roadmap, with named components, performance targets, and scheduled milestones.
The abandonment of Poseidon for layer 1 is therefore more than a technical footnote. It is a statement about priorities. Security assumptions that have already survived decades of scrutiny now rank higher than marginal efficiency gains inside zero-knowledge proofs. In a space that sometimes chases novelty for its own sake, that restraint is refreshing.
Whether the 2027 and 2028 dates hold exactly is almost secondary. The direction itself is clear. Ethereum is preparing to live in a world where quantum computers exist, and it intends to do so with cryptography that does not require an act of faith in a single specialized construction. That seems like the right kind of ambition for a network that already secures hundreds of billions in value.
The next few years will show how smoothly the transition unfolds. Client teams will implement leanVM. Auditors will examine the circuits. Researchers will keep pushing the performance of binary-field proofs. Users will continue using the chain largely unaware of the cryptographic machinery beneath. And somewhere in the background, the long research effort that once centered on Poseidon will be remembered as a necessary exploration that ultimately pointed the protocol toward simpler, more durable foundations.
In the end, the most durable cryptography is often the least exotic. Ethereum appears to have rediscovered that truth after eight years of deep research. The network is better for it.
