New Quantum Proposal Offers Bitcoin Holders a Private Proof of Control

Concerns surrounding the impact of quantum computing on Bitcoin have long been intertwined with the issue of Satoshi Nakamoto's holdings. Approximately 1.1 million bitcoin, valued at around $84 billion and attributed to the pseudonymous creator, remain in older wallets with exposed public keys, rendering them susceptible to potential theft by powerful quantum computers. The most straightforward defense against this threat is a soft fork that would eventually render spends from legacy address types obsolete, thereby forcing holders to transition to quantum-resistant formats before attackers can derive their private keys. However, this solution poses a dilemma for long-dormant holders like Satoshi, who would be required to publicly reclaim their assets or risk losing access to them. In response to this challenge, Dan Robinson of Paradigm has introduced a proposal for Provable Address-Control Timestamps (PACTs), which allows holders to generate a proof of ownership without having to move their coins. This is achieved by creating a cryptographic commitment using a random salt and BIP-322, a standard for signing messages from a Bitcoin address without spending from it. The commitment is then timestamped through OpenTimestamps, a free service that anchors data onto the Bitcoin blockchain, and remains private until the holder needs to spend their coins. If Bitcoin implements a soft fork that freezes quantum-vulnerable coins, the protocol could include a rescue path that accepts a STARK proof, showing that the holder created their commitment before the existence of quantum hardware. This approach addresses a specific gap in the existing proposal by providing a rescue path for wallets derived through BIP-32, the deterministic key generation standard introduced in 2012. Nevertheless, the implementation of PACTs requires Bitcoin to adopt a STARK verification protocol, which would necessitate a separate soft fork with broad community consensus. Ultimately, the success of PACTs in protecting Satoshi's holdings hinges on whether the creator or current controller of those keys makes the commitment, as no PACT can be retroactively created if Satoshi is indeed gone.