Blockstream researchers propose Bitcoin quantum-signature design to limit transaction capacity hit

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Bitcoin quantum signature proposal

Highlights

Blockstream researchers proposed SHRINCS, a post-quantum signature scheme for Bitcoin, designed to balance quantum resistance and minimize transaction throughput loss.
SHRINCS signatures start at 324 bytes and enable about three transactions per second, versus 0.36 for NIST SLH-DSA and 6.5 for current Schnorr signatures.
SHRINCS introduces one-time keys and operational complexities, remains unaudited, and would require a Bitcoin soft fork and broad consensus for adoption.

Signature design aims to balance security and throughput

As first reported by CoinDesk, researchers at Blockstream published a Thursday proposal for SHRINCS, a post-quantum transaction-signing method designed specifically for Bitcoin. The proposal addresses a long-running concern that a sufficiently powerful quantum computer could derive a private key from a public key visible on the blockchain, allowing forged signatures and unauthorized spending.

Bitcoin currently relies on elliptic-curve cryptography and compact Schnorr signatures to prove coin ownership without exposing private keys. But post-quantum signature schemes approved by the U.S. National Institute of Standards and Technology, or NIST, are far larger, creating a space problem in Bitcoin blocks and sharply reducing the number of transactions the network can process.

Blockstream estimates Bitcoin can handle about 6.5 transactions per second using current Schnorr signatures, compared with about 0.36 if every transaction used NIST-standardized SLH-DSA. SHRINCS is meant to narrow that trade-off, starting at roughly 324 bytes versus 64 bytes for Schnorr and reaching about three transactions per second with 580-byte signatures.

The design uses SHA-256, the hash function already embedded across Bitcoin, including mining. Jonas Nick, who developed SHRINCS with fellow Blockstream researcher Mikhail Kudinov, describes it as the first concrete post-quantum signature proposal built specifically for Bitcoin, while also saying it is not intended to be the network's final signature system or the best choice on every metric.

Adoption hurdles and wider crypto implications

SHRINCS also introduces operational complexity because it uses a fresh one-time key each time a wallet signs a transaction. That means wallet software has to track which keys have already been used across devices, hardware wallets and backups, and losing or restoring outdated key records could make spending harder or risk loss of funds in some wallet setups.

The proposal itself says a formal security proof is still pending, and the reference software has not completed a formal security audit and is not intended for production use. Blockstream says it demonstrated SHRINCS-signed transactions in March on Liquid, its separate blockchain aimed at faster and more private transfers of bitcoin and other assets.

Any move to bring SHRINCS to Bitcoin would require a soft fork, meaning a backward-compatible rules change, as well as broad agreement across the network to activate it. The proposal arrives as other blockchain ecosystems are also examining quantum-resistance, with Ethereum researchers earlier this week proposing validator deposit changes that could eventually allow new cryptographic key types.

Our earlier report on U.S. authorities’ seizure of the QScan and QTRouter domains detailed a court-authorized operation aimed at disrupting China-linked cyber tools used to scan and infect IoT devices and to mask the origin of malicious traffic. We noted that officials framed the move as part of a broader campaign to weaken hostile infrastructure and improve defenses around critical services by combining technical takedowns with threat-intelligence sharing.

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