Google’s latest whitepaper on quantum computing has reignited debate over how much time the crypto industry really has to prepare for a post-quantum future. The paper suggests that current cryptographic assumptions may no longer be safe by 2029, a timeline that computer scientist and Fhenix founder Guy Zyskind says makes the once-familiar “10-year migration window” look dangerously optimistic. In his view, the industry should treat the warning as a prompt for immediate action rather than a distant theoretical concern.
A shorter timeline for migration
Zyskind argues that the impact of the paper comes not only from its claims, but from the source behind it. Because Google is a major force in quantum research, its decision to attach a specific deadline to the threat has pushed the discussion beyond academic speculation. One of the most alarming points is the paper’s claim that a “cryptographically relevant quantum computer” could achieve a 41% success rate in hijacking a transaction before confirmation. If that becomes feasible, attackers could exploit the mempool, derive private keys in real time, and replace legitimate transfers with fraudulent ones.
To address that risk, Zyskind says blockchain systems need a full move to post-quantum cryptography (PQC), with lattice-based cryptography currently standing out as the most mature option. He also supports encrypting mempools, ideally with PQC and fully homomorphic encryption (FHE). In addition to reducing quantum-era exposure, encrypted mempools could also help mitigate front-running, MEV extraction, and broader transaction privacy concerns.
Bitcoin and Ethereum face different quantum risks
The whitepaper has also revived comparisons between Bitcoin and Ethereum at the structural level. For Bitcoin, the main concern remains straightforward: signature exploits that could enable direct theft of coins. Ethereum, however, relies on a broader stack of protocols, including Layer 2 systems and ZK-rollups, which creates a more complex threat surface. Zyskind warns that zero-knowledge systems built on elliptic curve cryptography would not merely weaken under sufficiently strong quantum computing—they could become completely broken. In that scenario, attackers could generate false proofs, misrepresent on-chain state, and steal funds.
Still, he notes that for ordinary asset transfers and state transitions, the remedy is clearer. Once Ethereum and its surrounding layers complete a transition to post-quantum secure cryptography, the immediate risk of theft can be neutralized. That means future-facing security can still be improved through upgrades, at least for standard network operations.
The bigger problem is retroactive decryption
The most difficult issue, according to Zyskind, is not future theft but retroactive decryption. Unlike a hijacked transaction, which is a one-off event, encrypted data stored on a public blockchain remains there permanently. A future quantum-capable adversary could collect that data today and decrypt it years later once sufficient computing power becomes available. That creates a major problem for privacy-preserving protocols: even if they upgrade in time, they may still be unable to protect historical user data that was already published on-chain.
For that reason, Zyskind argues that privacy systems should be treated as vulnerable unless they are designed from the ground up with post-quantum secure encryption. This is why he and the Fhenix team support rapid adoption of stronger encryption standards before 2029. In the quantum era, the challenge for blockchain privacy is no longer limited to securing the next transaction. It is also about preventing the past from being opened up years later.