Bitcoin Gets Quantum-Secure: Inside the New SHRINCS BIP Proposal

Blockstream Research has published a new Bitcoin Improvement Proposal (BIP) for SHRINCS, a post-quantum signature scheme designed to shield Bitcoin from future quantum attacks. Published on August 27, 2026, the proposal marks what Blockstream researcher Jonas Nick called "the first concrete proposal for a post-quantum signature scheme designed specifically for Bitcoin." The initiative is notable given that Blockstream co-founder and CEO Adam Back has publicly regarded quantum computing as a distant threat, yet his company is now leading the charge on practical defenses. "The safe thing is to prepare well in advance," Back told Cointelegraph earlier this year.

The core challenge is signature size. Current post-quantum schemes endorsed by the National Institute of Standards and Technology produce signatures 38 to 123 times larger than Bitcoin's existing ECDSA and Schnorr signatures. Deploying any of them naively could crater Bitcoin throughput to a fraction of one transaction per second. Ethereum's post-quantum team plans to sidestep this by aggregating block-level signatures into a single zero-knowledge proof, an approach also under consideration for Bitcoin that could actually boost throughput. Blockstream, however, has kept its proposal separate from that radical structural change.

Nick was candid about SHRINCS's limitations, stating it "is not intended to be Bitcoin's 'final' signature scheme, and it is not optimal along every axis," though he described it as "a very good trade-off among the options we have now." SHRINCS has already been proven in production on Blockstream's Liquid sidechain, giving the proposal real-world validation before it enters Bitcoin's BIP review process.

The stakes are enormous: once sufficiently powerful quantum computers arrive, they could reverse-engineer private keys from public keys exposed on-chain, putting billions of dollars in Bitcoin at risk. While the timeline for cryptographically relevant quantum machines remains hotly debated among scientists, the race to upgrade Bitcoin's signature layer is now formally underway, with SHRINCS serving as a concrete first step rather than an endpoint.