A Bitcoin Improvement Proposal for the post-quantum signature scheme SHRINCS has been published, putting a concrete Bitcoin-focused option into the debate over how the network could defend itself against future quantum attacks. The proposal comes from research led by Blockstream, whose team has already tested SHRINCS in production on the Liquid sidechain. Blockstream Research’s Jonas Nick described it as the first concrete post-quantum signature proposal designed specifically for Bitcoin, while also stressing that it is not meant to be Bitcoin’s final signature system and is not optimal in every respect. The core appeal is size. Existing post-quantum schemes endorsed by the National Institute of Standards and Technology are far larger than Bitcoin’s current ECDSA and Schnorr signatures, creating a major throughput problem if deployed directly on-chain. SHRINCS is still much bigger than Schnorr, but materially smaller than many alternatives, and Blockstream’s estimates suggest Bitcoin could still run at roughly 3 transactions per second under SHRINCS, versus 0.5 TPS for ML-DSA and 0.36 TPS for SPHINCS+. The catch is that SHRINCS is still early. Its BIP says the security proof remains unfinished, and the design introduces statefulness, signature growth over time, and a large fallback recovery path if a signing device is lost. Blockstream is also exploring lattice-based signatures and zero-knowledge proof aggregation, which it estimates could lift Bitcoin throughput to 6.7 TPS if combined with SHRINCS.

Vaulted CEO David McAlvany said Bitcoin could disappear within the next four years because of advances in quantum computing, according to Forbes, though he also acknowledged he cannot say when such a breakthrough might actually arrive. He said Bitcoin would face an existential problem if quantum machines become capable of quickly solving the mathematical problems that protect private keys. As of mid-2026, however, no quantum computer exists that can break Bitcoin’s cryptography. The concern described in the report is tied to the pace of future quantum development rather than any security breach that has already happened. Estimates cited in the report show that a large share of BTC sits in addresses with exposed public keys: Galaxy Digital put the number at about 7 million BTC, worth roughly $470 billion, while Glassnode estimated 6.04 million BTC, or 30.2% of supply. The report also outlined an active debate over how Bitcoin should respond. BIP-360 would add quantum-resistant address types, while BIP-361 would phase out old signature support, a move that could permanently freeze coins that are not migrated in time. Supporters say that outcome would be preferable to theft and forced selling by quantum attackers, while critics see it as confiscation.

BOLTS Technologies launches a pilot on Canton Network to integrate quantum-resilient technology (QFlex), protecting over $6 trillion in real-world assets from potential Q-Day threats.