Hardy Index Quantum readiness benchmark

What changed · What changed

Bitcoin Cash entered the index above Bitcoin, and the gap needs explaining

Neither chain changed how it signs. The difference sits in the scripting layer, and one weak dimension keeps the gap wider than it may stay.

The Hardy Index · Published 25 August 2026 · Every dated event below carries a primary source.

The short answer

Bitcoin Cash entered the index on 16 August 2026, rated well above Bitcoin. Nothing changed in either chain's signature scheme: both still sign with ECDSA and Schnorr on secp256k1. What moved the placement is a mainnet vault template that verifies a post-quantum signature inside Bitcoin Script. It is opt-in, not a default.

What moved and why

The 2026 upgrade, known as Layla, bundled four improvement proposals: Loops, Functions, Pay to Script and Bitwise. It reached Bitcoin Cash mainnet in May 2026. Together they made a design called Quantumroot practical.

Quantumroot is a vault: a contract you send coins into so that spending them needs a different kind of signature. That signature is LM-OTS, short for Leighton-Micali One-Time Signatures. It is a hash-based scheme, which means its security rests on SHA-256 rather than on the elliptic-curve maths a quantum computer is expected to break. LM-OTS is the one-time signature underneath LMS, which NIST approves in SP 800-208. The verification runs inside Bitcoin Script, so no change to the base protocol was needed. Wallets including OPTN Labs and Paytaca shipped support.

So a Bitcoin Cash holder can park coins behind a post-quantum signature on mainnet today. A Bitcoin holder cannot. This index ranks preparation, and on that measure the two chains are no longer in the same position.

Where this stands today

As rated by the Hardy Index, current as of 2 October 2026. Ratings change when the evidence does, and every change is recorded in the changelog.

What this does not mean

It does not mean Bitcoin Cash is quantum-safe by default. Ordinary addresses still sign with ECDSA and Schnorr on secp256k1, exactly as before. If you do nothing, nothing about your coins has changed.

  • The vault is opt-in at the contract level. You have to move coins into it deliberately.
  • LM-OTS keys are one-time. A hash-based scheme of this shape has usage limits, and the vault design works around them rather than removing them.
  • This is an application built on script features, not a new protocol signature type.
  • The placement uses the most generous reading available. If you think only protocol-level features should count, you would rate this chain a tier lower and take roughly fifteen points off. The profile says that out loud.

The weak dimensionBitcoin Cash inherits Bitcoin's chain history to August 2017, including every pre-fork pay-to-public-key output whose key is already published on chain. Nobody has measured exposed supply on Bitcoin Cash. That dimension is scored from the address model at the floor of its band, which is a published limitation of the rubric, not a finding.

How it got here

Dates for the standard and the deployment.

  1. NIST publishes SP 800-208, approving stateful hash-based signature schemes including LMS, whose one-time signature is LM-OTS. source
  2. Post-quantum vaults verifying LM-OTS in Bitcoin Script go live on Chipnet, a Bitcoin Cash test network. source
  3. The 2026 upgrade, bundling the Loops, Functions, Pay to Script and Bitwise CHIPs that Quantumroot depends on, activates on Chipnet, the preview network that runs six months ahead of mainnet. source

If you hold BCH

You have an option most holders of large-cap chains do not: you can move funds behind a hash-based signature without waiting for a protocol change. That option comes with the operational care any one-time signature scheme needs, so read the wallet documentation before you move size.

If you leave coins in a normal address, your position is close to Bitcoin's. Our quantum-safe wallets guide covers what opt-in protection actually requires, and will quantum computers break Bitcoin explains the exposed-key problem both chains share.

One number would change this rating. If somebody publishes a count of exposed supply on Bitcoin Cash at levels similar to Bitcoin's measured 4 million to 7 million coins, that dimension falls sharply and this gap narrows. We would like to see it published. Any change will appear in the changelog.

Where to go next

Sources

Every dated event above carries its own primary source. These are those sources, each checked on the date shown.

  1. Quantumroot: post-quantum vaults on Bitcoin Cash Bitauth / bitjson · primary · checked 25 August 2026
  2. Bitcoin Cash Upgrade 2026 Bitauth / bitjson · primary · checked 25 August 2026
  3. Quantumroot on Chipnet Bitauth / bitjson · primary · checked 25 August 2026
  4. SP 800-208: Recommendation for Stateful Hash-Based Signature Schemes NIST Computer Security Resource Center · primary · checked 25 August 2026
  5. Quantumroot vaults go live on CashVM The Quantum Insider · secondary · checked 25 August 2026

This is a security-readiness assessment, not investment advice.