Ethereum is revising its post-quantum strategy: abandoning Poseidon2 and seeking new solutions.
An important technical turning point is brewing in the Ethereum ecosystem. Protocol developers have decided to abandon plans to use the Poseidon2 hash function as the sole cornerstone for the post-quantum validator key registry. This is not a spontaneous move, but the result of deep cryptanalysis that revealed potential weaknesses in algebraic hash functions—a class of algorithms to which Poseidon2 belongs.
My analysis of the situation shows that the problem lies in the very nature of algebraic constructions. They are optimized for efficient operation in zero-knowledge proof systems, but this same algebraic structure can open up vectors for attacks that are less obvious for classical hash functions. That is why the team is in no hurry to reach a final verdict and is considering a broader range of candidates.
Among the alternatives currently on the negotiating table are the earlier version, Poseidon1, as well as the time-tested BLAKE3 and the SHA family. Each of these options has its own trade-offs: while Poseidon1 retains some performance advantages for zk-SNARKs, BLAKE3 and SHA offer greater cryptographic conservatism and years of battle-testing across various protocols.
Notably, the Ethereum Foundation has already allocated $1 million to a bug bounty program for Poseidon. This is a signal that the organization takes the threat of quantum computing with full seriousness. Post-quantum protection is not a matter of the distant future, but an engineering challenge that must be solved before quantum computers become powerful enough to break current digital signature schemes.
The final choice of algorithm will have long-term consequences for the entire network: from the security of user funds to transaction processing speed. Dragging out the process here is justified, because the price of a mistake is not just technical debt, but a potential catastrophe for trust in the platform.
My expert conclusion: The current pause in the selection is a sign of Ethereum's maturity as an institution. The market often underestimates the importance of such "quiet" technical decisions, but they are precisely what determine whether the network will survive the next decade. I recommend that investors and developers closely monitor the development of this issue—it could become a catalyst for updating security standards across the entire crypto space.