Over 100 researchers utilizing AI coding agents were able to lower the resource score in a very important part of quantum attack against Bitcoin by 86.1%, according to a paper published on September 9. This development is not a breakthrough in hacking Bitcoin or recovering a private key. Rather, it illustrates that only software optimization can dramatically decrease the quantum resources necessary for elliptic-curve arithmetic.
The main issue is not that “Q-Day” is quickly approaching. However, the real problem is that each technical advancement that brings the cost of performing a quantum attack down gives Bitcoin and various other blockchains less time to make a successful and secure transition to post-quantum security.
What ECDSA.Fail actually optimized
Eigen Labs introduced ECDSA.Fail in late May as a challenge to make secp256k1 point addition circuits more efficient. Different designs were scored by multiplying the maximum number of logical qubits used by the average number of Toffoli gates executed.
The score dropped from 10.75 billion to 1.496 billion on July 26. The top score used 1,151 logical qubits and about 1.3 million Toffoli gates, but later attempts saw the gate count dip below a million, and one design only needed 813 qubits. According to Decrypt, the researchers were exploring whether the math behind the problem worked and did not really hack a Bitcoin wallet.
“Although its timing remains uncertain, migration away from vulnerable cryptography is already under way,” the researchers wrote.
A full attack still needs a machine nobody has built
The end-to-end estimate from IonQ shows that it would take approximately 1,457 logical qubits and 39 million Toffoli gates in order to realize a full secp256k1 attack. The result corresponds to 19,397 physical trapped-ion qubits and takes about 25.7 days of processing time. IonQ claims that the hardware in question fits into the plans that the company established for around 2028.
According to calculations done by Google researchers, either 1,200 logical qubits and 90 million Toffoli gates or 1,450 logical qubits and 70 million gates are needed to conduct a complete secp256k1 attack efficiently. Their circuit can run in minutes with less than 500,000 physical qubits, enabled by a superconducting model.
The numbers being referenced cannot be straightforwardly compared to ECDSA.Fail. The reason is that the optimization procedure done by ECDSA.Fail only applies to a point-addition subroutine. The fault-tolerant hardware required for a real attack still does not exist.
Where Bitcoin is already exposed
According to Glassnode, there is 6.04 million $BTC at risk of a quantum attack, or 30.2 percent of the current supply, since the corresponding public key is available on the blockchain. Of the total, there are 1.92 million $BTC exposed in the output category and 4.12 million $BTC in terms of behavior, for example, due to address reuse.
The second risk arises when the public key that was hidden becomes public at the moment of spending. A fast enough computer theoretically has the ability to compute the private key before the transaction has been confirmed.
Patches that help, and where they stop
BIP 360 introduces a new type of output called Pay-to-Merkle-Root that eliminates the threat of Taproot’s key-path spending option, which is susceptible to quantum attacks. While this will protect coins whose public keys are visible for extended periods, it unfortunately does not address the quantum risk that exists for a limited time after a transaction is in the mempool and does not provide automatic migration of coins to the new format.
StarkWare has also demonstrated a quantum-safe Bitcoin transaction on mainnet, as Cryptopolitan previously reported. The method requires hours of off-chain GPU work, uses a nonstandard miner-direct route, and cannot protect coins whose public keys are already exposed.
Avihu’s breakthrough is important because it gives the psychological reassurance which we need and which the asset itself needs.
– StarkWare CEO Eli Ben-Sasson
In practical terms, it offers breathing room, not a cure. Ben-Sasson still favors a protocol-level solution.
The migration window, not the machine, is the risk
The greater challenge lies in governance. As stated in a report from the Coinbase Independent Advisory Board on Quantum Computing and Blockchain, close to 1.7 million $BTC spread over about 20,000 early P2PK public keys is stored in wallets believed to be under the control of Satoshi himself or of those who have lost their access. Setting a deadline for migration of these coins could freeze them or there is the risk of someone cracking them and taking them.
The goal for Ethereum is to achieve quantum resistance across execution, consensus and data by December 2029; in addition, the company intends to prepare for Q-Day as early as 2030. The G7 Cyber Expert Group, meanwhile, has called for coordinated efforts of post-quantum migration in the finance sector.
Therefore, Bitcoin faces market risks before it confronts any quantum concerns, especially the ambiguity around migration processes, custodial methods, and dormant coins that can potentially cause issues well before a technology capable of decrypting secp256k1 gets created.
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