Brief
One day, quantum computers may be able to derive private keys from exposed public keys and empty Bitcoin wallets – this is the hypothetical “Q-day” – but such machines do not exist yet, and there are significant differences in the timeline for their development.
The fixes can be roughly divided into three categories, and this week's news covers all three: implementing quantum-resistant transactions under the existing rules, protocol upgrades similar to soft forks, and defenses at the hosting layer.
There is no published content this week that can make Bitcoin inherently quantum-resistant on its own. However, the field is working to reduce defense costs while assessing the speed at which the threat is approaching.
Every few months, there are new headlines warning that quantum computers may one day be able to crack Bitcoin. This week, we've seen three such headlines in a row: a breakthrough in cost, a new privacy design, and a manual for hosting operations. This is precisely the right time to distinguish between real threats and mere noise.
Firstly, there is the issue itself, and it is a very real one. Bitcoin uses elliptic curve cryptography to protect wallets, a mathematical system that links private keys with public keys. If quantum computers become powerful enough to run the Shor algorithm, in theory, it would be possible to derive private keys from exposed public keys, forge signatures, and empty wallets.
The industry refers to the day when such hypothetical machines become a reality as "Q Day." Currently, there are no such computers in existence, and estimates for when they will appear vary greatly; however, the timeline is constantly being shortened, which is also why the preparatory work is accelerating.
The repair solutions are divided into three categories, and there is new information for each category this week.
The first category is to make quantum-resistant transactions feasible under the existing rules of Bitcoin. Last month, the first quantum-resistant Bitcoin transaction was mined on the mainnet by StarkWare. This week, it was also announced that an open competition – AI – in which a particular model came top of the rankings – managed to reduce the estimated cost of building such transactions from about $320 to about $67 in just one week.
However, according to the company itself, this is only a temporary measure. These transactions are not standard transactions, and they can only protect coins whose public keys have not yet been exposed. StarkWare still believes that a soft fork is the better long-term solution.
The second category is the protocol upgrade path – modifying Bitcoin itself to adopt post-quantum signatures. This is a more sustainable solution, but Bitcoin's decentralized governance means that such upgrades take many years to design, test, and deploy, and it is only recently that the community has begun to seriously discuss this issue.
The third category is defense at the hosting level. This week, the person in charge of cryptography at Coinbase introduced how this exchange, which manages assets worth approximately $250 billion, constructs a post-quantum hosting solution to adapt to any signature scheme that Bitcoin may ultimately adopt. If the chosen standard is not compatible with the key splitting technology that hosting institutions rely on today, a hardware backup solution will also be provided.
In conclusion, the so-called “Q-day” remains just a hypothesis, and it is very likely that many years will pass before it actually occurs; there is no single release this week that could make Bitcoin quantum-resistant on its own. This week has shown that the field is moving from theory to practical implementation, while working to reduce defense costs and assessing the speed at which the threat is approaching.
The actual preparation time that the crypto industry truly has is the actual gap between these two numbers.
