Recently, I delved into the threat of quantum computing to the blockchain ecosystem and discovered that the underlying implications behind Google's paper are much deeper than they appear on the surface.
Let's start with the core issue: by re-optimizing the implementation of Shor's algorithm on quantum circuits, Google reduced the logical qubits needed to crack 256-bit elliptic curve encryption from 6,000 down to 1,200. This isn't a hardware breakthrough, but the computational cost has dropped by a factor of 20, which is truly shocking. In other words, the once seemingly distant threat now has a concrete timeline.
Google's key milestone is set for 2029. This means that by then, HTTPS, SSL certificates, SSH remote login, and the ECDSA signature systems relied upon by public blockchains like Bitcoin and Ethereum will all need to upgrade to quantum-resistant cryptography. A three-year window sounds tight, but moving from theory to practical implementation requires substantial engineering work. Nonetheless, this at least signals that the window for updating post-quantum encryption algorithms has opened — it's not an emergency to act tomorrow, but further delay is no longer an option.
Regarding attack vectors, the situation is actually quite complex. On the Bitcoin chain, approximately 25% to 35% of addresses have exposed public keys, including early P2PK format addresses and all reused addresses. Once quantum computing matures, these addresses could be cracked and intercepted within the 10-minute window when transactions enter the mempool, potentially paralyzing the entire network. Ethereum faces an even more direct threat: each EOA account's transaction exposes the public key on-chain, and since the proof-of-stake mechanism relies on signature verification, if the signature algorithm isn't upgraded, the entire network becomes meaningless.
The most challenging aspect is that blockchain transaction history is permanently traceable. Even if quantum attacks are not yet feasible, all transactions that have exposed public keys in the past are recorded, waiting for quantum machines to mature and become potential targets. It's like a ticking time bomb, waiting to explode.
Fortunately, there are solutions. Ethereum has already been working on engineering optimizations, pushing account abstraction to allow EOA addresses to switch signature schemes at the application layer, and migrating validator signatures to post-quantum cryptographic algorithms. Ethereum's greatest advantage is its ability to upgrade dynamically; once the direction is clear, post-quantum transformations are just a matter of time. Bitcoin has adopted the BIP-360 scheme, which can incorporate post-quantum signature algorithms like FALCON or CRYSTALS-Dilithium. Technically, it's not difficult, but reaching consensus is. The Bitcoin community has argued over block size for years; imagine how hard it would be to implement a hard fork for post-quantum security. But once the threat becomes "certain," even the most complacent developer communities will be forced to accept this lifesaving patch.
Interestingly, Google chose to disclose this potential quantum risk using zero-knowledge proofs. From a certain perspective, this is a clever "soft landing" approach, because if things go out of control, the consequences could be not just blockchain collapse but the destruction of the entire internet civilization. Moreover, Google Quantum AI has researchers from the Ethereum Foundation, hinting that post-quantum capabilities might become a core competitive advantage for future blockchains. It makes sense — the essence of blockchain is cryptography, and this new mission could be crucial for the entire crypto ecosystem.
