The cost of preparing for quantum computer attacks on Bitcoin has fallen to $59, or about 80,000 won. With GPU software optimisation sharply reducing the computing cost needed for quantum-resistant transactions in a little over 2 months, attention is focusing on ways to protect some coins without changing Bitcoin network rules. The current cost is a simulation-based estimate rather than money spent to complete an actual transaction, leaving hurdles before real-world use.

CryptoSlate, a blockchain outlet, reported on Oct. 13 local time that in an open competition run by StarkWare, Yukon Research and Eigen Labs, the estimated computing cost for quantum-resistant Bitcoin transactions fell from about $320 in August to $67 in September and $59 on Oct. 13. The researchers improved efficiency through GPU software optimisation and set a next goal of cutting the cost to below $10.

The technology drawing attention is called Quantum Safe Bitcoin, or QSB. StarkWare's Avihu Levy (아비후 레비) demonstrated in August that a quantum-resistant spending structure can be implemented without changing Bitcoin's consensus rules. The method combines hash-based cryptography and computational puzzles to protect specific Bitcoin holdings from quantum computer attacks.

The key is to create a separate protection mechanism without a full upgrade of the Bitcoin network itself. Introducing quantum-resistant cryptography at the protocol level requires development, verification and a network consensus process, but QSB has been presented as a transitional alternative that can protect some assets within existing rules.

The researchers are improving efficiency by performing the computation needed for transactions in advance outside the blockchain. The open competition also used artificial intelligence-assisted coding tools. According to the latest results, Nvidia's RTX 4090 GPU processed more than 1 billion verification candidates per second. That marks a sharp improvement from an initial throughput of about 146 million.

Still, the $59 figure should not be taken as the actual cost of a transaction. It is a hardware-dependent estimate derived by simulating GPU workloads and does not include Bitcoin network fees. Some computation steps are also based on assumptions, so further verification is needed on whether the same cost and performance can be achieved in a real operating environment.

Faster development of quantum-resistant technology is being driven by concerns that Bitcoin's existing cryptographic system could become vulnerable to future quantum computers. Google Quantum AI in March published research that sharply lowered earlier estimates of the quantum computing resources needed to attack the elliptic-curve cryptography used in Bitcoin. Assuming certain hardware conditions, it analysed that some attacks could theoretically be carried out within minutes using fewer than 500,000 physical qubits. That is about 20 times lower than previous estimates.

Such research does not mean Bitcoin's cryptographic system can be broken immediately. No quantum computer capable of carrying out the attack has been publicly implemented, but calls are growing to prepare security measures in advance in case development speeds up.

Bitcoin with public keys already exposed could be a potential target. Glassnode research found that about 6.04 million BTC, or 30.2 percent of the Bitcoin supply at the time, had public keys exposed on-chain. Of that, about 1.92 million BTC had public keys exposed due to the address structure itself, while the remaining about 4.12 million BTC were counted as exposed due to address reuse or past spending history.

If a sufficiently powerful quantum computer emerges, concerns have been raised that an attacker could derive private keys from public keys and steal the assets. Developers are therefore considering steps to introduce quantum-resistant cryptography into the Bitcoin protocol, along with measures that can progressively protect existing holdings.

QSB is seen as an emergency response tool that can be used during such a transition. But its protection scope is limited. It is advantageous for assets that can be moved while existing public keys have not been exposed, while coins already exposed remain vulnerable if an attacker appears before holders complete a safe transfer.

Network accessibility for actual use is also a challenge. QSB transactions comply with Bitcoin's consensus rules but may be rejected under typical network relay policies. That means they must be submitted directly to miners willing to process them. During the August demonstration, Mara's Slipstream service provided such a transaction route.

Ultimately, lower computing costs for quantum-resistant transactions alone do not solve Bitcoin's quantum security problem. Cost-cutting effects must be proven in real transaction formats, and a path must be secured to deliver transactions reliably to miners. Over the long term, a protocol-level upgrade remains an important task.

Even if the researchers succeed in pushing computing costs below $10, or about 13,500 won, practical applicability is expected to be determined in transaction verification and network processing. A key point to watch is how effectively the Bitcoin ecosystem can put in place a workable protection system before the threat from quantum computers becomes a reality.