Paradigm Bitcoin general partner Dan Robinson published a proposal on May 1 for Provable Address-Control Timestamps, or PACTs, a system that lets dormant Bitcoin holders privately timestamp proof of key ownership before quantum computers arrive, creating a potential rescue path for Satoshi Nakamoto’s estimated 1.1 million BTC.
Summary
- PACTs use three steps: a secret salt, a BIP-322 ownership proof, and an OpenTimestamps commitment anchored on-chain, all without any public on-chain transaction.
- If Bitcoin later implements a quantum sunset soft fork, PACT holders can submit a STARK zero-knowledge proof to reclaim coins while keeping their keys hidden.
- Robinson wrote that Satoshi revealing keys in any forced migration would mean having to “tell the world that they are alive and still in possession of their keys.”
Robinson published PACTs on May 1, framing the design as a hedge against what he calls the Satoshi Problem inside Bitcoin’s quantum threat discussion. The official Paradigm post outlined the dilemma: if quantum computers arrive before Bitcoin adapts, old addresses with exposed public keys face theft.
If Bitcoin rushes a sunset soft fork to freeze those addresses, dormant holders face a forced, public coin migration. PACTs offer a third path, letting holders timestamp proof of ownership silently in 2026 without doing anything further until a rescue mechanism is standardised.
As crypto.news reported, approximately 1.7 million BTC remain in quantum-exposed address types, including Satoshi-linked wallets worth roughly $75 billion.
The proposal builds on BIP-361, authored by Casa CSO Jameson Lopp, which defines a phased migration away from legacy signatures after which unmigrated coins would be frozen.
Bitcoin.com noted that Robinson acknowledged multisig, complex scripts, and hardware wallet support would all require further standardisation, and that Bitcoin may never implement a quantum sunset.
As crypto.news documented, Bitcoin’s quantum debate has been intensifying in 2026 after Blockstream CEO Adam Back argued at Paris Blockchain Week for optional, opt-in quantum-resistant upgrades rather than forced wallet freezes, directly challenging the BIP-361 approach PACTs are designed to complement.
As crypto.news tracked, Naoris Protocol CEO David Carvalho warned that dormant wallets including Satoshi’s would be “ripe for the picking” once quantum computers reach sufficient capability, and that a quantum hack on Bitcoin “would lead to a real loss of trust” in the asset.
