--- title: Is Aptos quantum-safe? chain: Aptos ticker: APT hardy_score: 40.5 rank: 11 of 23 tier: "3: Committed" url: "https://hardyindex.com/chains/aptos" updated: 2026-08-12 methodology_version: 1.1 --- # Is Aptos quantum-safe? **Hardy Score 40.5 / 100. Rank 11 of 23. Tier 3: Committed. As of 12 August 2026.** No, not today. Aptos accounts sign with Ed25519, which a sufficiently large quantum computer would break. Aptos has proposed adding SLH-DSA-SHA2-128s, the hash-based signature scheme standardised by NIST as FIPS 205, for transaction signatures. The proposal is unusually candid about the cost: signatures would be 7,856 bytes, roughly 82 times larger than an Ed25519 signature, and verification takes about 294 microseconds, roughly 4.8 times slower. The compensating argument is conservatism, because SLH-DSA relies on SHA-256, a hash function blockchains already depend on heavily, so adopting it introduces very few new cryptographic assumptions. Existing Ed25519 accounts would continue to work normally, with the post-quantum scheme offered to those who opt in. > This is a security-readiness assessment, not investment advice. ## Summary Proposed SLH-DSA-SHA2-128s for transaction signatures as an opt-in scheme, accepting signatures 82 times larger than Ed25519 in exchange for minimal new security assumptions. ## Score breakdown | # | Dimension | Score | Weight | Contribution | |---:|---|---:|---:|---:| | 1 | Signature scheme | 0/10 | 30% | 0.0 | | 2 | Deployment stage | 5/10 | 25% | 12.5 | | 3 | NIST alignment | 9/10 | 15% | 13.5 | | 4 | Migration path | 6/10 | 15% | 9.0 | | 5 | Exposure | 2/10 | 10% | 2.0 | | 6 | Verification | 7/10 | 5% | 3.5 | | | **Hardy Score** | | | **40.5** | ### 1. Signature scheme: 0/10 Aptos transactions are signed with Ed25519 today and nothing post-quantum protects live APT. The SLH-DSA scheme is a proposal rather than a deployed mainnet feature. Source: https://github.com/aptos-foundation/AIPs ### 2. Deployment stage: 5/10 Tier 3: Committed. A specific scheme with published performance characteristics has been proposed and is under active work, with nothing post-quantum live on mainnet. Source: https://github.com/aptos-foundation/AIPs ### 3. NIST alignment: 9/10 SLH-DSA-SHA2-128s is a parameter set of FIPS 205, a final NIST standard published in August 2024, not a candidate awaiting publication. Choosing a hash-based standard also means the security rests on SHA-256, which the chain already depends on. Source: https://csrc.nist.gov/pubs/fips/205/final ### 4. Migration path: 6/10 Existing Ed25519 accounts keep working and the post-quantum scheme is offered opt-in, which avoids a forced migration. The deductions are that protection is therefore not automatic for existing holders, and that the proposal had not been adopted on mainnet at the time of writing. Source: https://github.com/aptos-foundation/AIPs ### 5. Exposure: 2/10 Aptos is an account-model chain and an account's authentication key is published on-chain when it first transacts, so effectively all economically active supply has an exposed key and is harvestable today. Source: https://github.com/aptos-foundation/AIPs ### 6. Verification: 7/10 The proposal is public and states its own costs precisely, including signature size and verification time, which is a form of honesty that is easy to check and easy to get wrong. Aptos is open source. The deduction reflects that this is a proposal rather than shipped and audited code. Source: https://csrc.nist.gov/pubs/fips/205/final ## Signature scheme - **On mainnet today:** Ed25519 for account authentication - **Post-quantum scheme:** SLH-DSA-SHA2-128s proposed for transaction signatures, offered opt-in alongside Ed25519 - **NIST standard:** FIPS 205 (SLH-DSA), finalised August 2024 - **Readiness tier:** Tier 3: Committed. A funded roadmap with public dates and active research exists, but no post-quantum signature is live on mainnet. ## Roadmap - **August 2024** (shipped): NIST finalises SLH-DSA as FIPS 205, giving Aptos a published standard to propose against. Source: https://csrc.nist.gov/pubs/fips/205/final - **2026** (proposed): Aptos proposes SLH-DSA-SHA2-128s for transaction signatures, with 7,856-byte signatures and roughly 4.8 times slower verification, offered opt-in while existing Ed25519 accounts continue to work. Source: https://github.com/aptos-foundation/AIPs ## Exposure Aptos publishes an account's authentication key on-chain once the account transacts, so in practice every economically active account has an exposed key that can be recorded today against a future quantum computer. Aptos accounts do support key rotation, which is a useful primitive for a future migration because it lets an account change its authentication key without moving funds to a new address, but rotation does not undo the exposure of a key that has already been published. ## Frequently asked questions ### Is Aptos quantum-safe? No, not today. Aptos accounts sign with Ed25519, which a sufficiently large quantum computer would break. Aptos has proposed adding SLH-DSA-SHA2-128s, the hash-based signature scheme standardised by NIST as FIPS 205, for transaction signatures. The proposal is unusually candid about the cost: signatures would be 7,856 bytes, roughly 82 times larger than an Ed25519 signature, and verification takes about 294 microseconds, roughly 4.8 times slower. The compensating argument is conservatism, because SLH-DSA relies on SHA-256, a hash function blockchains already depend on heavily, so adopting it introduces very few new cryptographic assumptions. Existing Ed25519 accounts would continue to work normally, with the post-quantum scheme offered to those who opt in. ### Is Aptos quantum-safe? No. Aptos accounts authenticate with Ed25519, which a sufficiently large quantum computer would break. Aptos has proposed adding SLH-DSA-SHA2-128s as an opt-in post-quantum signature scheme, but that proposal is not live on mainnet. ### Why did Aptos choose a scheme with such large signatures? Because it minimises new assumptions. SLH-DSA is hash-based and relies on SHA-256, a function blockchains already depend on heavily, so adopting it adds very little new cryptography to trust. The cost is size and speed: signatures of 7,856 bytes, about 82 times larger than Ed25519, and verification roughly 4.8 times slower. ### Would existing Aptos accounts have to migrate? Not under the proposal as published. Existing Ed25519 accounts would continue operating normally, with SLH-DSA offered only to holders who opt in. That avoids forcing a migration, but it also means existing accounts are not protected by the upgrade itself. ### How does Aptos compare with the other committed chains? Its algorithm choice is among the strongest, because SLH-DSA is a final NIST standard and hash-based schemes carry the most conservative security assumptions in the set. Its weakness is the same as its peers: nothing is live on mainnet, so the signature dimension, which carries 30 per cent of the score, earns nothing. ## What this rating means if you hold Aptos Plain-language guidance from the same publication, with no product recommendation attached. - [Is my crypto safe from quantum computers?](https://hardyindex.com/guides/is-my-crypto-safe-from-quantum-computers.md) - [How to protect your crypto from quantum computers](https://hardyindex.com/guides/how-to-protect-crypto-from-quantum-computers.md) - [All guides](https://hardyindex.com/guides.md) Nothing on this profile is sponsored and nothing on it is an affiliate link. See https://hardyindex.com/how-we-make-money.md. ## Sources 1. [Aptos Improvement Proposals](https://github.com/aptos-foundation/AIPs): Aptos Foundation (GitHub) (primary, checked 12 August 2026) 2. [FIPS 205: Stateless Hash-Based Digital Signature Standard (SLH-DSA)](https://csrc.nist.gov/pubs/fips/205/final): NIST (primary, checked 12 August 2026) 3. [Safeguarding cryptocurrency by disclosing quantum vulnerabilities responsibly](https://research.google/blog/safeguarding-cryptocurrency-by-disclosing-quantum-vulnerabilities-responsibly/): Google Research (primary, checked 12 August 2026) --- Methodology: https://hardyindex.com/methodology (v1.1). Cite as: The Hardy Index, "Aptos", https://hardyindex.com/chains/aptos, as of 12 August 2026.