did:ethr vs did:btcr: EVM vs Bitcoin DIDs

Full EVM Composability: Integrates with smart contracts on Ethereum, Polygon, Arbitrum, and other L2s. This matters for DeFi logins, token-gated access, and automated credential verification via protocols like EAS (Ethereum Attestation Service).

On-Chain Document Updates & Revocation: Supports key rotation, service endpoint updates, and attribute management directly on-chain. This matters for dynamic credentials, enterprise use cases, and compliance with W3C DID Core specifications using libraries from Spruce ID and Veramo.

Unforgeable Bitcoin Anchoring: DID document hash is permanently embedded in a Bitcoin OP_RETURN transaction. This matters for long-term, high-value attestations where tamper-proof provenance is critical, leveraging Bitcoin's ~$1.3T security budget.

One-Time Creation Cost: After the initial Bitcoin transaction (~$2-$10), the DID is permanently established with no ongoing chain fees. This matters for scaling static identities (e.g., academic degrees, notarizations) where updates are rare.

Recurring Gas Fees for Management: Every key rotation or attribute update requires paying network gas fees on Ethereum mainnet or an L2. This matters for applications with frequent credential updates, where cost can become prohibitive.

Static Document, No On-Chain Updates: The DID document is immutable after creation; key rotation requires creating a new DID. This matters for active user identities needing recovery mechanisms or integration with dynamic DeFi/Social protocols.

Seamless Smart Contract Interaction: DIDs are managed via a smart contract (EthereumDIDRegistry), enabling direct integration with DeFi, DAOs, and dApps. This is critical for on-chain identity verification and programmable attestations.

• Use Case: Building a credential system for a DAO's governance or a DeFi protocol's KYC.

Mature W3C Compliance: Implements the DID Core and Verifiable Credentials specs with libraries like ethr-did-resolver and veramo. Supported across Polygon, Arbitrum, and other L2s.

• Use Case: Teams needing to issue verifiable credentials within a broad, interoperable EVM environment.

Bitcoin's Security Guarantees: DIDs are anchored directly into Bitcoin's blockchain via OP_RETURN. This provides the highest assurance of tamper-proof existence proofs, leveraging Bitcoin's ~$1T+ security budget.

• Use Case: Archival or notarization systems where proof-of-existence must be valid for decades.

No Smart Contract Risk: Operates on Bitcoin's base layer, avoiding upgradable contract or governance key centralization risks. The DID document is constructed from the immutable transaction chain.

• Use Case: Maximally decentralized identity systems where avoiding any single point of control is paramount.

Variable & Potentially High Fees: DID operations (create, update, revoke) require gas payments on the underlying EVM chain. While cheap on L2s (<$0.01), mainnet updates can cost $5-$50+ during congestion.

• Trade-off: Operational cost and speed are tied to network conditions.

No Native Smart Contract Logic: Lacks built-in mechanisms for key rotation, delegation, or complex attestations without significant external infrastructure. Updates are cumbersome.

• Trade-off: Sacrifices feature richness for maximal simplicity and security.

Unparalleled Security via Bitcoin's Proof-of-Work: Anchors identity to the most secure and immutable blockchain (over 600 EH/s hash rate). This matters for long-term, high-value identity assertions where resistance to tampering is paramount.

Limited Functionality & High On-Chain Cost: Lacks a native smart contract environment for complex attestations or key rotation. Writing to the Bitcoin chain is expensive (~$5-50 per transaction) and slow (~10 min/block). This matters for applications requiring frequent updates or rich credential schemas.

Rich Ecosystem & Programmable Identity: Leverages the full EVM stack (Solidity, ERC-725, ERC-1056) for advanced logic like social recovery, credential revocation, and delegation. Integrated with tools like Spruce ID's Sign-In with Ethereum. This matters for dApps needing dynamic, composable identity layers.

Security Relies on EVM's Consensus: Subject to the security and social consensus of the Ethereum network and its L2s (Optimism, Arbitrum). While secure, it doesn't match Bitcoin's singular focus on immutable settlement. This matters for purists who prioritize maximal decentralization and censorship resistance above all else.