EURC EURC

Claim: Circle has published a Post-Quantum Security Roadmap (May 2026) identifying quantum threats across blockchain layers (transaction signatures, consensus, smart contracts, infrastructure). No EURC-specific formal cryptographic inventory exists.

Coverage basis: Public documentation and roadmap

Implementation score: 0.25 · Evidence confidence: Medium

Issue classification: assurance-only caveat · Score treatment: note-only

Assurance: Roadmap covers Arc blockchain and general infrastructure; no EURC-specific inventory or threat model published.

Circle's PQ whitepaper inventories quantum-vulnerable layers at a general level. No chain-by-chain or contract-by-contract inventory for EURC deployments exists.

• https://6778953.fs1.hubspotusercontent-na1.net/hubfs/6778953/PDFs/quantum_paper.pdf
• https://www.circle.com/blog/preparing-blockchains-for-q-day

Claim: EURC smart contracts are open-source and verifiable on-chain. Circle's PQ whitepaper and blog posts provide some evidence. Third-party analyses (LlamaRisk, MEXC/EternaX) document admin key architecture.

Coverage basis: Open-source code, on-chain data, third-party analysis

Implementation score: 0.25 · Evidence confidence: Medium

Issue classification: assurance-only caveat · Score treatment: note-only

Assurance: No formal quantum-specific evidence record exists. Third-party analysis partially fills the gap.

The codebase is publicly available and verifiable but no quantum-scoped audit or formal cryptographic evidence record has been published for EURC.

• https://github.com/circlefin/stablecoin-evm
• https://etherscan.io/token/0x1abaea1f7c830bd89acc67ec4af516284b1bc33c
• https://llamarisk.com/research/2025-04-22t19-28-41-000z

Claim: EURC user transfers are authorized by host-chain ECDSA/Ed25519 signatures (Ethereum: ECDSA; Solana: Ed25519; Stellar: Ed25519; etc.). No PQ or hybrid-PQ protection exists for any user spend path.

Coverage basis: Inherited from host chains; standard ERC-20 / SPL / Stellar token

Implementation score: 0 · Evidence confidence: High

Issue classification: quantum-critical vulnerability · Score treatment: score-reducing

Quantum blocker: All user spend authorization is ECDSA/Ed25519-only with no PQ migration path on any host chain.

Assurance: Inherited vulnerability from host chains. Well-established and verifiable on-chain.

Per QRI Section 7.2, standard tokens inherit host-chain QRI for spend authorization.

• https://etherscan.io/token/0x1abaea1f7c830bd89acc67ec4af516284b1bc33c
• https://developers.circle.com/stablecoins/eurc-contract-addresses

Claim: EURC holders use host-chain accounts. Ethereum EOAs that have sent transactions have permanently exposed ECDSA public keys (long-exposure attack window). Solana Ed25519 addresses also expose public keys on first spend.

Coverage basis: Inherited from host chains

Implementation score: 0 · Evidence confidence: High

Issue classification: quantum-critical vulnerability · Score treatment: score-reducing

Quantum blocker: Long-exposure public keys on Ethereum (transacted EOAs) and other chains are permanently vulnerable to offline quantum key-recovery attacks.

Assurance: Standard blockchain architecture limitation; well-documented across all major L1s.

This is an inherited vulnerability. EURC cannot independently fix host-chain address exposure design.

Claim: EURC is a token, not a chain. No validator signatures, VRF, or consensus layer is applicable at the token level.

Coverage basis: Not applicable — token inherits host chain consensus

Implementation score: 0 · Evidence confidence: High

Issue classification: none · Score treatment: not applicable

Consensus-layer quantum risk is evaluated at the host-chain level (Ethereum, Solana, etc.), not at the token level.

Claim: EURC's state integrity depends on: (1) host-chain consensus (quantum-vulnerable), (2) admin EOAs using ECDSA that can upgrade proxy contracts, mint tokens, pause transfers, and modify blacklists.

Coverage basis: On-chain admin key architecture

Implementation score: 0 · Evidence confidence: High

Issue classification: quantum-critical vulnerability · Score treatment: score-reducing

Quantum blocker: Admin EOAs using ECDSA can mint unlimited EURC, upgrade proxy to malicious implementation, or permanently freeze all transfers if compromised by a quantum attacker.

Assurance: Admin roles verified on-chain by LlamaRisk (April 2025). Audits by ChainSecurity, Kudelski, and Halborn cover classical security but not quantum threat model. No timelock exists on admin operations.

Admin keys are EOAs (possibly MPC-backed per Circle operational practice but unverifiable on-chain). Roles include: owner, admin (proxy), pauser, blacklister, masterMinter, and multiple minters.

• https://etherscan.io/token/0x1abaea1f7c830bd89acc67ec4af516284b1bc33c
• https://github.com/circlefin/stablecoin-evm
• https://llamarisk.com/research/2025-04-22t19-28-41-000z

Claim: EURC has no privacy layer. All transactions and balances are publicly visible on host chains.

Coverage basis: No privacy layer exists

Implementation score: 0 · Evidence confidence: High

Issue classification: none · Score treatment: not applicable

Circle's Arc blockchain plans quantum-safe privacy features, but these do not apply to current EURC deployments.

Claim: EURC is a token, not a blockchain. It has no P2P network layer.

Coverage basis: Token has no P2P layer

Implementation score: 0 · Evidence confidence: High

Issue classification: none · Score treatment: not applicable

Claim: Circle's admin EOAs controlling EURC use ECDSA signatures for all operations (mint, upgrade, pause, blacklist). No PQ or hybrid-PQ wallet/custody workflow exists for admin operations.

Coverage basis: On-chain admin key architecture

Implementation score: 0 · Evidence confidence: Medium

Issue classification: quantum-critical vulnerability · Score treatment: score-reducing

Quantum blocker: Admin key custody relies entirely on classical ECDSA; no evidence of PQ-protected signing workflows for critical token operations.

Assurance: Circle may use MPC or cloud KMS for key management, but this cannot be verified on-chain and does not change the ECDSA dependency. Circle's PQ roadmap Section 4.1 discusses migrating cold storage to PQ multi-signature smart contracts but this is a future plan, not current production.

Circle's PQ whitepaper Section 4.1 discusses migrating cold storage to PQ multi-signature smart contracts but this is a future plan, not current production.

• https://etherscan.io/token/0x1abaea1f7c830bd89acc67ec4af516284b1bc33c
• https://llamarisk.com/research/2025-04-22t19-28-41-000z

Claim: Zero percent of EURC value-at-risk is protected by PQ or hybrid-PQ cryptography. All circulating supply (~€368M as of June 1, 2026) remains quantum-vulnerable.

Coverage basis: Total circulating supply across all chains

Implementation score: 0.05 · Evidence confidence: High

Issue classification: quantum-critical vulnerability · Score treatment: score-reducing

Quantum blocker: 100% of EURC value-at-risk remains quantum-vulnerable with no protection coverage.

Assurance: Coverage score of 1 out of 20 per QRI coverage thresholds (<25% protected).

EURC's PQ-Recoverable status means value could theoretically be restored after an attack, but this is recovery, not protection.

• https://www.circle.com/eurc

Claim: No critical wallets (admin EOAs, Circle treasury, exchange custody wallets, major protocol integrations) are protected by PQ cryptography.

Coverage basis: Admin keys and major holders

Implementation score: 0 · Evidence confidence: Medium

Issue classification: quantum-critical vulnerability · Score treatment: score-reducing

Assurance: Top holders include Coinbase cold wallets and institutional depositors. None have published PQ migration attestations.

Claim: Admin EOAs have been identified as vulnerable by third-party analysis (LlamaRisk). Circle's PQ roadmap acknowledges the general vulnerability of ECDSA-based smart contract admin paths. No formal deprecation, freeze, or migration plan exists for these control paths on existing chains.

Coverage basis: Third-party analysis and Circle roadmap

Implementation score: 0.25 · Evidence confidence: Medium

Issue classification: assurance-only caveat · Score treatment: note-only

Assurance: Identification is partial and comes primarily from third-party research rather than Circle's own published inventory.

• https://llamarisk.com/research/2025-04-22t19-28-41-000z
• https://6778953.fs1.hubspotusercontent-na1.net/hubfs/6778953/PDFs/quantum_paper.pdf

Claim: Circle published a Post-Quantum Security Roadmap (May 2026) covering Arc blockchain with phased PQ feature deployment. The roadmap mentions that upgradeable proxy contracts CAN be upgraded for PQ support but provides no EURC-specific timeline, activation criteria, or chain-by-chain migration plan.

Coverage basis: Circle PQ whitepaper and blog posts

Implementation score: 0.25 · Evidence confidence: Medium

Issue classification: operational/product caveat · Score treatment: note-only

Assurance: Roadmap is focused on Arc, a new L1 blockchain not yet on mainnet. Section 4.2 discusses USDC/smart contract PQ upgrades but provides no dates, specifications, or EURC-specific details for existing chain deployments.

The roadmap is a credible public document from Circle but constitutes a proposal/plan (IS 0.25) rather than a detailed migration roadmap with sequencing and activation criteria.

• https://6778953.fs1.hubspotusercontent-na1.net/hubfs/6778953/PDFs/quantum_paper.pdf
• https://www.circle.com/blog/preparing-blockchains-for-q-day

Claim: No PQ or hybrid-PQ account creation, wallet tooling, transaction paths, custody paths, user-facing warnings, education, or migration prompts exist for EURC on any chain.

Coverage basis: No PQ user-facing infrastructure

Implementation score: 0 · Evidence confidence: High

Issue classification: quantum-critical vulnerability · Score treatment: score-reducing

Assurance: Circle's Programmable Wallets and Modular Wallets products support EOA and smart-contract accounts but with classical cryptography only.

The Arc blockchain plans to offer PQ signature support via SLH-DSA-SHA2-128s precompile, but this is not available on any chain where EURC currently exists.

Claim: No enforcement mechanisms exist for EURC migration. No deadlines, deprecated signing paths, restricted withdrawals, or mandatory migration requirements. No exchange, custody, bridge, or wallet coordination for PQ migration has been established.

Coverage basis: No enforcement or coordination

Implementation score: 0 · Evidence confidence: High

Issue classification: quantum-critical vulnerability · Score treatment: score-reducing

Assurance: Circle's PQ roadmap Section 5 discusses potential future delisting of non-compliant blockchains and hard-switch scenarios, but these are policy discussions, not active enforcement mechanisms.

Claim: Circle operates a bug bounty program via HackerOne and has a public vulnerability disclosure process. No quantum-specific incident-response playbook or governance process has been published for EURC.

Coverage basis: Existing security processes

Implementation score: 0.25 · Evidence confidence: Low

Issue classification: assurance-only caveat · Score treatment: note-only

Assurance: General security processes exist but no quantum-specific IR playbook is public. The PQ roadmap discusses account recovery approaches (Section 5.2) but these are conceptual, not operational.

Circle's PQ whitepaper Section 5.2 describes technical approaches for account recovery (move to Arc, seed-phrase ZK recovery, TEE-attested recovery, off-chain recovery) but these are research proposals for Arc, not implemented processes for current EURC.

• https://www.circle.com/legal/mica-eurc-whitepaper

Claim: No PQC or hybrid-PQC algorithms are deployed anywhere in EURC's production scope. Circle's Arc roadmap proposes SLH-DSA-SHA2-128s, a NIST-standardized scheme, but this is not used for EURC.

Coverage basis: No PQC deployment

Implementation score: 0.25 · Evidence confidence: Medium

Issue classification: operational/product caveat · Score treatment: note-only

Assurance: Circle's choice of SLH-DSA-SHA2-128s for Arc is consistent with NIST standards and industry direction, but this provides zero assurance for current EURC.

• https://6778953.fs1.hubspotusercontent-na1.net/hubfs/6778953/PDFs/quantum_paper.pdf

Claim: EURC smart contracts have been audited by ChainSecurity, Kudelski, Halborn, and others for classical security. No quantum-scoped audit exists for any EURC component.

Coverage basis: Existing classical audits

Implementation score: 0 · Evidence confidence: Medium

Issue classification: assurance-only caveat · Score treatment: note-only

Assurance: Existing audits cover classical implementation correctness, access control, and upgrade safety. None evaluate quantum threat models or PQC migration readiness. This is expected given no PQC implementation exists to audit.

Per QRI Section 6.4, scope-mismatched audits support only the audited component. Since no quantum-critical implementation exists, no quantum-scoped audit is possible.

• https://www.circle.com/legal/mica-eurc-whitepaper

Claim: EURC smart contracts are fully open-source under Apache 2.0 license in the circlefin/stablecoin-evm repository. Contracts are verifiable on block explorers. Non-EVM implementations (Solana, Stellar) are also publicly documented.

Coverage basis: Public GitHub repositories and block explorers

Implementation score: 1 · Evidence confidence: High

Issue classification: none · Score treatment: not applicable

Assurance: Full source code available. Contract verification confirmed on Etherscan and equivalent explorers for other chains.

This subfactor scores on general implementation openness. The contracts implement classical cryptography (ERC-20 standard) correctly and openly, but this does not imply quantum safety.

• https://github.com/circlefin/stablecoin-evm
• https://etherscan.io/token/0x1abaea1f7c830bd89acc67ec4af516284b1bc33c

Claim: EURC uses upgradeable proxy contracts (UUPS pattern) that allow contract logic to be replaced without changing token addresses. This architecture could theoretically support future PQ signature schemes. No documented PQ parameter agility plan exists.

Coverage basis: Upgradeable proxy architecture

Implementation score: 0.25 · Evidence confidence: Medium

Issue classification: assurance-only caveat · Score treatment: note-only

Assurance: Proxy upgrade capability exists and is proven (EURC has undergone multiple upgrades, e.g., to FiatTokenV2_2). However, no PQ-specific upgrade path has been designed, specified, or tested.

The upgradeable proxy pattern provides architectural flexibility but the absence of a PQ parameter agility plan means this remains at the proposal/design stage for quantum purposes.

• https://github.com/circlefin/stablecoin-evm/blob/master/doc/upgrade.md
• https://www.circle.com/legal/mica-eurc-whitepaper

Claim: No stateful PQ signatures (XMSS, LMS, SLH-DSA) are used in EURC. Subfactor is not applicable to the current production scope.

Coverage basis: No stateful signatures deployed

Implementation score: 0 · Evidence confidence: High

Issue classification: none · Score treatment: not applicable

Assurance: Circle's Arc roadmap proposes SLH-DSA-SHA2-128s which is a hash-based stateful scheme; anti-reuse controls and state management would need evaluation if/when deployed for EURC.

Claim: No PQ signatures are deployed for EURC, so no performance analysis is applicable to the current production scope.

Coverage basis: No PQ deployment

Implementation score: 0 · Evidence confidence: High

Issue classification: none · Score treatment: not applicable

Assurance: Circle's PQ roadmap acknowledges performance challenges (SLH-DSA signature size of 7,856 bytes, verification costs) and discusses batch verification and fraud-proofs as mitigation.