New Proposal Offers Potential Solution for Bitcoin's Quantum Computing Conundrum

The specter of quantum computing has long posed a threat to Bitcoin's security, with millions of coins in older wallets potentially at risk of theft due to exposed public keys. This vulnerability extends to the approximately 1.1 million bitcoin attributed to the cryptocurrency's enigmatic creator, Satoshi Nakamoto, valued at around $84 billion. One possible defense against this threat is a soft fork that phases out the use of legacy address types, thereby forcing holders to migrate to quantum-resistant formats before attackers can exploit their private keys. Prominent developer Jameson Lopp, along with five other developers, proposed this approach in mid-April through BIP-361, outlining a five-year timeline for the transition and freezing any coins that fail to migrate. However, this proposal presents a new dilemma: long-dormant holders, including Satoshi, would need to publicly reassert control over their assets or risk losing access to them. To address this issue, Dan Robinson has introduced the concept of Provable Address-Control Timestamps (PACTs), which enables holders to generate a private proof of ownership at a specific date without revealing any information publicly until they need to spend their coins. This process involves creating a random salt and using BIP-322 to produce a proof of ownership, which is then bundled with the salt and timestamped on the Bitcoin blockchain through OpenTimestamps. The resulting proof remains private and can be used to demonstrate control over the assets without revealing sensitive information. If Bitcoin implements a soft fork that freezes quantum-vulnerable coins, the protocol could incorporate a rescue path that accepts a STARK proof, a type of zero-knowledge proof that remains secure against quantum computers. This would allow holders to submit their proof when they want to spend their coins, and the network would release the funds without revealing any information about the original address, amount, or timestamp. PACTs also address a specific shortcoming in BIP-361 by providing a rescue path for wallets derived through BIP-32, the deterministic key generation standard introduced in 2012. However, this approach requires Bitcoin to adopt a STARK verification protocol, which would necessitate a separate soft fork with broad community consensus. The verification infrastructure required for PACTs does not currently exist in Bitcoin and would need significant development, including multisig wallets, complex scripts, and hardware wallet support. Ultimately, PACTs offer a potential solution to the conundrum posed by quantum computing, providing a way for holders to protect their assets without being forced to choose between security and dormancy.