A researcher at Paradigm outlined a new model that he says can protect dormant bitcoins, including those belonging to Bitcoin network creator Satoshi Nakamoto, from future quantum computing threats.
This proposal by Dan Robinson introduces what he calls “Provable Address-Control Timestamps,” or PACTs, which would allow Bitcoin (BTC) holders to prove they once controlled a wallet, in case quantum computing advances to the point of deriving wallet private keys—if that day ever comes.
This model leverages the existing timestamp system within blockchain's fundamental functions. Holders only need to generate a proof of control over their bitcoins and timestamp it on the blockchain to establish an ownership record for future quantum attacks. This proof can later be unlocked, allowing users to reclaim their funds on a future quantum-resistant version of Bitcoin.
This is a potential workaround to a major issue in the quantum bitcoin debate: how to protect the ownership and privacy of long-dormant bitcoin addresses.
According to similar proposals such as BIP-361, Casa's Chief Security Officer Jamison Lop and others have stated that wallets, exchanges, and custodians will have a multi-year migration window to transition away from the "legacy" signatures. After this period, any tokens that have not been migrated will become unusable.
However, this presents another set of issues for long-term inactive wallet holders. Transferring funds may reveal that the holder is still active and could potentially link this wallet to other wallets under their control.
The PACTs model aims to avoid this dilemma by allowing users to prove ownership without broadcasting it on-chain.
Robinson wrote, "This does not mean Bitcoin must decide today whether sunset protection is needed." He added that this gives users a way to prepare in advance, allowing them to "plant the seeds now" in case protection measures are needed in the future.
The Block team reached out to Dan Robinson for comment.
Quantum pressure
With advancements in quantum computing, cryptocurrency users and developers must plan together how to defend against potential threats.
Other researchers behind Lopp and BIP-361 warn that, due to public keys being visible, more than a third of circulating Bitcoin could be vulnerable to quantum attacks.
Meanwhile, real-world demonstration projects are also beginning to make progress. Last week, an independent researcher extracted a 15-digit elliptic curve key using quantum hardware, in what is claimed to be the largest such attack to date, even though Bitcoin relies on stronger 256-bit encryption.
There is no consensus on the timeline for “Q-day,” when quantum computers will be able to break modern cryptography. Google researchers recently suggested a transition to post-quantum cryptography around 2029, while others believe actual attacks may still be years or even decades away.