Blockstream Research says it has added post-quantum signature verification to Liquid, marking what it describes as the first time an actual transaction on the production Bitcoin sidechain has been signed with a post-quantum system. With the Bitcoin infrastructure, the importance is less about an emergency situation than proving that quantum-resistant devices can be tested in live conditions before the problem forces a problem.
The announcement focuses on Simplicity, Blockstream’s Liquid smart contract language. Rather than waiting for the development of network-wide consensus, the team used Simplicity to create a custom currency that allows users to lock assets into a contract that requires post-quantum signatures for use. Essentially, that means that Liquid users can access the quantum-oriented protection of LBTC and other issued assets, including stablecoins and tokenized securities, without changing the rules of Liquid’s consensus base.
How Blockstream Tackles the Bitcoin Quantum Threat
Blockstream framed that as a major achievement. “The traditional way to add post-quantum signatures would require consensus changes across the entire network—a slow, careful process that involves all stakeholders,” the research notes. But Siplicity, Blockstream’s smart contract language on Liquid, offers a different approach.”
The authenticator is based on SHRINCS, a post-quantum integrated hash signature design that Blockstream Research says was developed specifically for blockchain environments. The system includes an advanced mode intended for general use, which generates minimal signatures, and a stateless fallback mode designed for recovery situations so users can access funds even if they lose status. That two-track design addresses a practical problem in post-quantum cryptography: theoretical security is insufficient if the system is too complex for real-world wallet behavior.
Most importantly, Blockstream says this is not a lab simulation. The team streamed two live builds on the Liquid mainnet, one using high-level mode and the other using stateless rollback. Those transactions are secured with real value, and Blockstream said the method works not only for bitcoin in Liquid but for any asset issued on the network.
The note also highlighted additional symbolic details. Because Liquid requires transaction size to scale with a computational budget, the team had to fill in a lot of space in post-quantum operations. “Instead of plugging these transactions into zero, Blockstream has filled more space with the Bitcoin white paper—a nod to the project’s cypherpunk roots.”
However, the company was careful not to handle what was sent. “This guarantee does not make Liquid fully resistant to value,” the post said. “Several key components remain traditionally protected,” including Bitcoin’s peg, Private Asset bonds and the Liquid blockchain consensus protocol. In other words, this is a logical starting block, not a full response to the threat of future value.
That distinction is important in how development should be studied. The research note repeatedly emphasizes that cryptographically related quantum computers do not exist today and may not arrive for years or decades. But it says waiting until such machines are near would be a mistake, especially for systems like Bitcoin whose security assumptions are deeply tied to the classic ECDSA and Schnorr signatures.
“What we’ve done at Liquid—build, test, and deploy post-quantum solutions in production systems—is how we’re preparing Bitcoin’s infrastructure for the future,” Blockstream wrote. That may be the clearest takeaway here: not that Bitcoin has solved the quantum problem, but that one reliable method is starting to move from idea to production-grade testing.
At press time, BTC traded at $71,130.
The featured image was created with DALL.E, a chart from TradingView.com
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