Blockchain Quantum Readiness Index / Arbitrum One
L2 · EVM
Arbitrum One
Users and the transaction-posting sequencer sign with elliptic-curve keys; hybrid post-quantum smart accounts run only on the Arbitrum Sepolia testnet. A 12-member security council can upgrade the network with no delay in emergencies, and used that power in October 2026. Its fraud proofs are hash-based, but they read transaction data through Ethereum's elliptic-curve KZG checks, so they are not quantum-safe either. No official post-quantum roadmap was found.
Last reviewed 2026-10-19
Is Arbitrum One quantum safe?
Not yet. Arbitrum One is at Stage 3 (Testnet) in LimeChain's Blockchain Quantum Readiness Index, with a progress score of 16.5/100. Post-quantum accounts run on a testnet, or on mainnet without keeping funds safe at rest, so users cannot rely on them yet. Still exposed or unproven: consensus, proof system, bridges & messaging, admin & upgrade keys.
What Arbitrum One needs for Stage 4: Live option
- Stage 4 needs PQ user accounts on mainnet that keep funds at rest out of reach of ECC keys (U is: testnet, hold: hidden-until-spend)
Caps and adjustments
- P: mechanism hash-based-fault-proof is vulnerable (component KZG is vulnerable: Shor's algorithm breaks discrete logarithms in pairing groups. Forged openings can make a verifier accept wrong blob data.) -> treated as exposed
- B: mechanism hash-based-fault-proof is vulnerable (component KZG is vulnerable: Shor's algorithm breaks discrete logarithms in pairing groups. Forged openings can make a verifier accept wrong blob data.) -> treated as exposed
- cap 40: users cannot hold and spend funds under a production PQ mechanism on mainnet
- cap 60: consensus PQ not even on testnet
Rosette slices
| Slice | State | Points | Weight | Reason & evidence |
|---|---|---|---|---|
| U User keys | Testnet At rest: Hidden until first spend Arbitrum One keeps Ethereum's account model (EOAs keep the same address), so the best option is a never-spent secp256k1 EOA whose address is a Keccak-256 hash of the public key. No production PQ smart account is deployed here (the Kohaku PQ ERC-4337 account exists only on Arbitrum Sepolia and Ethereum Sepolia). |
6/10 | 25 | EOAs verify secp256k1 ECDSA. The official ethereum/kohaku pq-account (ERC-4337, ML-DSA or Falcon plus ECDSA, both required) is deployed on Arbitrum Sepolia (factory 0xF451...8C2e, 6,500 bytes of code, measured 2026-10-19); nothing comparable is on mainnet. A single-developer hackathon ML-DSA account on mainnet (RaYYeR220/qanary, unaudited, one demo account) is not counted as a usable account type. |
| C Consensus | Exposed | 0/10 | 20 | The sequencer's DataPoster signs L1 batch-posting transactions with a standard Ethereum (secp256k1) key; no PQ sequencer path is cited. no evidence |
| P Proof system | Exposed vulnerable hash-based-fault-proof Hash-based (Merkle history commitments + WASM one-step proofs) claimed “live-pq” without valid evidence |
0/10 | 10 | BoLD is active: disputes bisect Merkle history commitments to a single WASM instruction verified by a one-step proof contract, with no elliptic-curve component in proof verification. Bonds are ETH in the Rollup contract; validation is permissionless (the allowlist was removed). The fault proof reads blob data through the EIP-4844 KZG point-evaluation precompile (OneStepProverHostIo), so a forged KZG opening could win a dispute. |
| B Bridges & messaging | Exposed vulnerable hash-based-fault-proof Hash-based (Merkle history commitments + WASM one-step proofs) claimed “live-pq” without valid evidence |
0/10 | 15 | Trustless verification is the BoLD dispute system on Ethereum L1: withdrawals finalize only after an assertion survives the challenge period, whose proof machinery is hash-based. The fast path relies on the ECC-signed sequencer feed (see C) but can be bypassed via the delayed inbox. The fault proof reads blob data through the EIP-4844 KZG point-evaluation precompile (OneStepProverHostIo), so a forged KZG opening could win a dispute. |
| A Admin & upgrade keys | Exposed | 0/10 | 15 | The Security Council is a 12-member ECC multisig: 'Performing any Emergency Action requires a 9-of-12 approval from the Security Council' and it can 'execute any software upgrade or perform other required actions with no delay in order to respond to a security emergency'. Non-emergency DAO actions pass through AIP phases with multi-day waits; the emergency path has no delay. The council used this no-delay emergency power on 2026-10-02 (a BoLD settlement guard and a Stylus activation pause). |
| M Migration & recovery | Discussed | 1/10 | 15 | No official Offchain Labs / Arbitrum post-quantum roadmap exists. A post on the Arbitrum Foundation forum (2026-06-30) discusses ERC-4337 validator swaps and EIP-7702 as migration paths; it is not a plan. Sources 11 |
Stage gates
| Requirement | Status | Details & evidence |
|---|---|---|
| Current audit of the deployed PQ signing code (Stage 5) | Not met | not claimed |
| Exit window of at least 7 days before upgrades (Stage 5, L2s with ECC admin keys) | Not met | not claimed |
| Admin timelock of at least 30 days with a PQ override (Stage 6, alternative to PQ admin keys) | Not met | not claimed |
| Ratified migration plan with an activation date (Stage 6) | Not met | not claimed |
| New accounts PQ or hybrid by default (Stage 6) | Not met | not claimed |
| ECC sunset enforced (Stage 7) | Not met | not claimed |
PQ adoption published, not scored
There are no PQ accounts on mainnet yet. Having PQ accounts does not mean people move to them. This tracks the share of value and accounts that actually moved, over time.
Measured exposure
No on-chain probe run yet. Bitcoin, Solana, Cosmos and Substrate probes are planned.
Evidence and sources (11)
Every non-zero rating above cites at least one of these public sources.
- github.com/ethereum/kohaku/blob/master/packages/pq-account/de…
- raw.githubusercontent.com/ethereum/kohaku/master/packages/pq-…
- docs.arbitrum.io/build-decentralized-apps/arbitrum-vs-ethereu…
- docs.arbitrum.io/how-arbitrum-works/deep-dives/l1-to-l2-messa…
- ethereum.org/en/developers/docs/accounts/
- raw.githubusercontent.com/ZKNoxHQ/kohaku/master/packages/pq-a…
- docs.arbitrum.io/how-arbitrum-works/bold/gentle-introduction.md
- github.com/OffchainLabs/nitro-contracts/blob/main/src/osp/One…
- docs.arbitrum.foundation/dao-constitution
- forum.arbitrum.foundation/t/security-council-emergency-action…
- forum.arbitrum.foundation/t/post-quantum-cryptography-risk-in…
Source: chains/arbitrum-one.json. Reproduce: python3 score.py chains/arbitrum-one.json
Building on Arbitrum One?
LimeChain helps teams plan their post-quantum migration: what is exposed, what to change first, and the engineering to get there.
Talk to usOpen, repeatable scoring. Non-zero ratings need public evidence; missing evidence means unknown. Methodology v0.4 · mechanism registry 2026-10-13.