# Blockstream Proposes Quantum-Safe Bitcoin Signatures

**Published:** 2026-08-27T07:42:14.968Z  
**Topic:** Bitcoin  
**Sentiment:** neutral  
**Publisher:** TrendWatcher — https://www.trendwatcher.in/article/9c81df24-df96-4de0-a13c-770b7c67960b

Blockstream researchers propose SHRINCS, a quantum-resistant signature scheme for Bitcoin that aims for 3 transactions per second, compared to 0.36 for NIST

Blockstream researchers have published a proposal for SHRINCS, a new method for signing Bitcoin transactions designed to resist quantum computer attacks without severely limiting transaction throughput [1]. This development addresses a theoretical vulnerability where quantum computers could potentially derive private keys from public keys, threatening existing Bitcoin holdings, including over 1.1 million bitcoin belonging to Satoshi Nakamoto [1].

| At a glance | |
|---|---|
| Proposed Solution | SHRINCS (Signature Hash-based, Reusable, Iterated, Nested, Compact Scheme) [1] |
| Transaction Speed (SHRINCS) | ~3 transactions per second (tps) [1] |
| Transaction Speed (NIST standard) | ~0.36 tps [1] |
| Transaction Speed (Current Schnorr) | ~6.5 tps [1] |

## Addressing the Quantum Threat

Bitcoin's security relies on elliptic-curve cryptography for digital signatures, which allows users to prove ownership of funds without revealing their private keys [1, 2]. However, a sufficiently powerful quantum computer running Shor's algorithm could theoretically reverse-engineer public keys to expose private keys, enabling attackers to spend bitcoin [1]. This threat is specific to signature schemes; Bitcoin's SHA-256 mining process is not significantly affected by quantum computing [2].

The primary challenge in implementing quantum-safe signatures is their size. Post-quantum signatures standardized by the U.S. National Institute of Standards and Technology (NIST) are significantly larger than current Bitcoin signatures, which would drastically reduce the number of transactions that fit into a Bitcoin block [1]. Blockstream estimates that Bitcoin, currently capable of about 6.5 transactions per second (tps) with Schnorr signatures, would drop to approximately 0.36 tps using NIST's SLH-DSA hash-based scheme [1].

## SHRINCS: A Compact Alternative

SHRINCS aims to mitigate this size problem, allowing for roughly three transactions per second [1]. SHRINCS signatures start at about 324 bytes, compared to 64 bytes for Schnorr signatures, and grow by approximately 16 bytes with each key use [1]. This efficiency is partly due to Bitcoin's 2017 SegWit upgrade, which provides a discount for the signature portion of a transaction [1]. SHRINCS is built using SHA-256, the same hash function used in Bitcoin's mining system, avoiding the introduction of new mathematical assumptions [1].

Jonas Nick, who co-designed SHRINCS, noted it is the first post-quantum signature proposal specifically for Bitcoin, though not necessarily the final solution [1]. The system requires wallets to manage fresh one-time keys for each transaction, tracking used keys to prevent reuse. Restoring old wallet backups or losing this information could complicate spending [1].

The SHRINCS proposal is still in its early stages, lacking a completed formal security proof, and its reference software has not undergone a formal security audit [1]. Blockstream demonstrated SHRINCS-signed transactions on Liquid, a separate blockchain, in March [1]. Implementing SHRINCS on the Bitcoin mainnet would require a soft fork, a backward-compatible change to Bitcoin's rules, and broad network consensus [1].

## What to watch

*   **Security Proof Completion:** Monitor for the formal security proof of SHRINCS, which is currently pending [1].
*   **Software Audits:** Track progress on formal security audits for the SHRINCS reference software [1].
*   **Network Consensus:** Observe discussions and developments regarding potential soft fork proposals and network-wide agreement for integrating SHRINCS into Bitcoin [1].

The development of SHRINCS highlights the ongoing efforts within the Bitcoin community to proactively address theoretical future threats from quantum computing, balancing security enhancements with the practical constraints of network throughput.

## Sources
1. CoinDesk — [Bitcoin researchers propose quantum fix that would not crowd out transactions](https://www.coindesk.com/tech/2026/08/27/bitcoin-researchers-propose-quantum-fix-that-would-not-crowd-out-transactions)
2. Blockstream — [Bitcoin's Quantum Defense | Blockstream](https://blockstream.com/quantum/)

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Cite as: TrendWatcher, "Blockstream Proposes Quantum-Safe Bitcoin Signatures", https://www.trendwatcher.in/article/9c81df24-df96-4de0-a13c-770b7c67960b