Bitcoin's Quantum Computing Conundrum: Adam Back Advocates for Optional Upgrades

The specter of quantum computing has sparked intense debate among Bitcoin's prominent developers, yielding vastly differing opinions. Adam Back, CEO of Blockstream, addressed attendees at Paris Blockchain Week, emphasizing the need for Bitcoin developers to commence building optional quantum-resistant upgrades. This comes despite the fact that current quantum computers are still in the experimental phase, with progress being incremental over the past 25 years. Back stressed that preparation and controlled implementation are crucial, rather than reacting to a crisis. He highlighted Blockstream's experimentation with quantum-resistant transaction signatures on the Liquid network, a sister network to Bitcoin, and noted that the 2021 Taproot upgrade was designed to accommodate new signature methods without disrupting the network. Back's comments echo his previous stance, where he suggested that users would have around a decade to transition to quantum-resistant formats. However, the context has shifted with the introduction of BIP-361, a proposal by Jameson Lopp and five other developers, which outlines a fixed five-year timeline for phasing out quantum-vulnerable addresses and freezing non-compliant coins. This would affect approximately 1 million bitcoin attributed to Bitcoin's creator, Satoshi Nakamoto, and an estimated 5.6 million inactive coins. Back's approach can be seen as an implicit alternative to BIP-361's forced migration, as he believes that Bitcoin's developer community can respond swiftly to a sudden quantum breakthrough. He suggested that the community's rough-consensus governance could handle emergencies without pre-scheduled freezes. The disagreement between Back and Lopp represents the core of Bitcoin's quantum debate, with Back betting on the community's ability to coordinate quickly and Lopp advocating for a scheduled freeze to avoid a disorderly migration.