---
title: "CLSAG ring signatures: which blockchains use it"
url: "https://hardyindex.com/algorithms/clsag"
---

# CLSAG ring signatures

Linkable ring signatures over the curve behind Ed25519, used by Monero to hide which of several outputs is being spent. No standardised post-quantum replacement exists for this construction. Broken by Shor's algorithm on a cryptographically relevant quantum computer, which recovers the private key from the public key.

- **Quantum status:** Broken by Shor's algorithm on a cryptographically relevant quantum computer.
- **Standard:** No published standard.
- **Family:** elliptic curve.
- **Also known as:** Concise Linkable Spontaneous Anonymous Group signatures.

## Rated chains using it

- [Beldex](https://hardyindex.com/chains/beldex.md): privacy, mainnet, mandatory. Source (source code or release): https://github.com/Beldex-Coin/beldex/blob/dev/src/ringct/rctTypes.h
- [Monero](https://hardyindex.com/chains/monero.md): privacy, mainnet, mandatory. Source (statement or write-up): https://github.com/insight-decentralized-consensus-lab/post-quantum-monero/blob/master/writeups/semitechnical_summary.MD

## Sources

- [CLSAG implementation in the Monero node (src/ringct/rctSigs.cpp)](https://github.com/monero-project/monero/blob/master/src/ringct/rctSigs.cpp), Monero Project. Accessed 19 October 2026.