Paradigm Bitcoin general partner Dan Robinson unveiled a novel concept on May 1 designed to address a pressing threat to long-dormant Bitcoin holders. Termed Provable Address-Control Timestamps, or PACTs, the system enables owners of old Bitcoin addresses to generate cryptographic proof of key possession without exposing their coins or identity. This approach is particularly aimed at protecting wallets that predate modern security standards, including the legendary trove attributed to Satoshi Nakamoto.
PACTs operate through a three-step process that remains entirely off-chain. First, the holder creates a secret salt. Next, they generate a BIP-322 ownership proof. Finally, that proof is committed to an OpenTimestamps record, which is anchored to the Bitcoin blockchain. Crucially, no transaction is broadcast, preserving anonymity. If Bitcoin later adopts a quantum sunset soft fork to freeze vulnerable addresses, PACT holders could use a STARK zero-knowledge proof to migrate their coins without revealing their private keys.
The proposal emerges amid growing debate about quantum computing’s potential to crack Bitcoin’s elliptic curve cryptography. According to crypto.news, roughly 1.7 million BTC reside in exposed address types, with Satoshi-linked wallets alone holding an estimated $75 billion. Robinson explicitly acknowledged that a forced migration would compel Satoshi to disclose his identity, writing that revealing keys would require “telling the world that they are alive and still in possession of their keys.”
PACTs build on BIP-361, authored by Casa CSO Jameson Lopp, which outlines a phased migration away from legacy signatures and eventual freezing of unmigrated coins. However, Robinson conceded that multisig, complex scripts, and hardware wallet support require further standardization, and that Bitcoin may never implement a quantum sunset at all. This has fueled a broader conflict, with Blockstream CEO Adam Back arguing at Paris Blockchain Week for opt-in quantum-resistant upgrades rather than forced freezes.
Industry experts have underscored the stakes. Naoris Protocol CEO David Carvalho warned that dormant wallets, including Satoshi’s, would become “ripe for the picking” as quantum computers advance, and that a quantum hack on Bitcoin “would lead to a real loss of trust” in the asset. PACTs thus represent a pragmatic hedge, allowing holders to silently establish a claim that can be honored later without compromising their security or privacy.