Blockstream Runs Quantum-Proof Bitcoin Transactions on a Live Network
Blockstream has put post-quantum cryptography into a working Bitcoin sidechain, moving a threat most of the industry keeps filing under “someday.” The firm, run by Bitcoin veteran Adam Back, ran the first quantum-resistant signed transactions on the Liquid mainnet in March 2026. This wasn’t a test environment. Real money, real infrastructure, and cryptography built to withstand computers that haven’t been invented yet.
What the company shipped
At the center sits a signature scheme called SHRINCS. It’s hash-based, which means it doesn’t rely on the elliptic curve math that secures Bitcoin’s standard ECDSA signatures today. A powerful enough quantum computer could break that math. Hash-based signatures don’t hand quantum machines the same shortcut, so they hold up far better.
According to a July 13 report, Blockstream deployed SHRINCS through Simplicity smart contracts, and the interesting part is how quietly it happened. No changes to Liquid’s consensus rules. That means no forced upgrade and no hard fork fight. Anyone holding Liquid Bitcoin can move to quantum-resistant spending whenever they choose. Five post-quantum transactions have now run on the mainnet, a first for any production Bitcoin sidechain.
The company also floated a second protocol, SHRIMPS, aimed at the practical mess of managing these signatures across lots of devices. It supports up to 1,024 hardware wallets and keeps signatures at 2.5 KB. Size is important here. Post-quantum signatures tend to run large, and hardware wallets don’t have much memory or processing room to spare.
A slow on-ramp, not a scramble
Blockstream’s Jade hardware wallet will get firmware updates adding per-UTXO opt-in for quantum protection. Users apply it to specific outputs rather than migrating their entire setup at once. Nothing breaks in the process.
That caution matches how Back reads the clock. He estimates quantum computers capable of cracking ECDSA are 20 to 40 years out, and he’s proposing a ten-year migration window for Bitcoin users instead of any rush. I think he’s right to treat Liquid as the proving ground. Its users are mostly trading desks and exchanges settling large positions, a smaller and more technical crowd than Bitcoin’s general population. That makes it a sensible place to gather live performance data before anything comes near the Bitcoin mainnet.
The SHRIMPS proposal answers a problem custodians will hit long before quantum computers arrive. Corporate treasuries and individual holders lean on hardware wallets, and managing bulky signatures across a thousand-plus devices is an operational headache, not a hypothetical one. Blockstream started building for it early. Most of the field hasn’t started at all.