Adam Back Challenges BIP-361 Proposal at Paris Blockchain Week

The outcome of this debate could redefine Bitcoin's security protocols and affect millions of BTC currently at risk.

• Adam Back opposed the BIP-361 proposal during Paris Blockchain Week, which aims to freeze quantum-vulnerable Bitcoin addresses.
• 1.7 million BTC are at risk due to quantum computing threats, representing about 8% of Bitcoin's total supply.
• Community divided over the proposal, with proponents advocating for security and critics emphasizing voluntary consensus.

• Quantum computers threaten Bitcoin's legacy ECDSA signatures, particularly affecting pay-to-public-key addresses where public keys are exposed.
• BIP-361, introduced by Jameson Lopp and co-authors, proposes a phased approach to freeze unmigrated coins, raising concerns about censorship and expropriation.
• Incremental progress in quantum computing over the past 25 years has intensified discussions around Bitcoin's long-term security.

The debate surrounding BIP-361 is rooted in the growing concern over quantum computing's potential to compromise Bitcoin's security. Quantum computers, utilizing Shor's algorithm, can efficiently break the cryptographic signatures that secure Bitcoin transactions. This vulnerability primarily affects legacy pay-to-public-key (P2PK) addresses, where public keys are visible on the blockchain. An estimated 1.7 million BTC, including Satoshi Nakamoto's dormant holdings, are at risk, representing a significant portion of Bitcoin's total supply.

Jameson Lopp and five co-authors introduced BIP-361 on April 15, 2026, proposing a two-phase approach to mitigate this risk. Phase A would ban new payments to legacy addresses three years post-activation, while Phase B would invalidate old signatures five years later, effectively freezing coins that have not migrated to quantum-resistant addresses. This proposal aims to prevent what proponents term "intergenerational theft," where future quantum capabilities could allow malicious actors to access these vulnerable funds.

However, Adam Back, CEO of Blockstream, argues against the forced migration of coins, advocating instead for optional upgrades through Taproot, a Bitcoin improvement that enhances privacy and flexibility. Back's position emphasizes the importance of Bitcoin's core tenets: decentralization and voluntary consensus. He contends that preemptive freezes could be seen as protocol-level expropriation, undermining the very principles that Bitcoin was built upon. Back believes that Bitcoin's consensus mechanisms are robust enough to respond to crises without necessitating drastic measures like freezing funds.

The community remains divided, with some developers supporting BIP-361 for its proactive stance on security, while others, like Back, prioritize the preservation of Bitcoin's censorship resistance. The debate has sparked discussions about alternative solutions, such as BitMEX's proposal for a "canary fund" that would allow users to opt-in to quantum-resistant features without enforcing a blanket freeze.

As the conversation unfolds, the implications of this debate extend beyond technical specifications; they touch on the fundamental values that underpin the Bitcoin network and its community.

• Bitcoin holders: Those with assets in legacy addresses face potential risks if BIP-361 is implemented.
• Developers: Bitcoin developers are split, influencing future protocol upgrades and community consensus.
• Investors: Institutional and retail investors may reassess their strategies based on perceived security risks.
• Regulators: Regulatory bodies in regions like Dubai may need to address the implications of quantum threats on digital asset security.

• Community consensus: Monitor how the Bitcoin community responds to BIP-361 and whether a consensus emerges around security measures.
• Quantum computing advancements: Keep an eye on developments in quantum computing technology, as breakthroughs could accelerate the urgency of these discussions.
• Market reactions: Observe any shifts in Bitcoin's market performance or investor sentiment in response to the ongoing debate.