Level 3: Signed
A digital signature provides cryptographic proof of explicit consent to specific terms.
This section is advisory.
Overview
For explicit consent, the counterparty digitally signs the terms — for example, using EIP-712 typed data signing or a similar standard. This adds proof of intent: not only are the terms provable (Level 2), but there is cryptographic evidence that a specific party explicitly consented to those specific terms at a specific time.
This is the digital equivalent of a signed contract. The signature binds an identity to a document.
How It Works
When acceptanceRequired is true in legal-context.json, the service signals that it requires explicit acceptance before transacting:
{
"terms": "https://example.com/terms/v3.pdf",
"contentHash": "0x7f83b1657ff1fc53b92dc18148a1d65dfc2d4b1fa3d677284addd200126d9069",
"acceptanceRequired": true
}The flow:
- Agent discovers that
acceptanceRequiredistrue - Agent downloads the terms document
- Agent verifies the
contentHash(Level 2) - Agent (or the human principal) digitally signs the terms
- The signature — binding a specific identity to a specific document at a specific time — is recorded
- Transaction proceeds
What the Signature Proves
The combination of Level 2 (provable) and Level 3 (signed) creates a complete evidence chain:
| Evidence | What It Proves |
|---|---|
contentHash | The exact document that was in effect |
| Digital signature | A specific party consented to that document |
| Timestamp | When the consent was given |
| Identity binding | Who consented (tied to a verifiable identity) |
This is stronger than a traditional signature on paper. A paper signature can be forged. A digital signature on a hash-verified document cannot be repudiated — the signer either produced the signature or they did not.
Signing Standards
The LCP standard does not mandate a specific signing mechanism. Any digital signature standard is acceptable. Examples:
- EIP-712 — Typed structured data hashing and signing (Ethereum ecosystem)
- JSON Web Signatures (JWS) — Per RFC 7515 (web ecosystem)
- XML Digital Signatures — Per W3C recommendation (enterprise ecosystem)
- Qualified Electronic Signatures — Per eIDAS for EU regulatory compliance
The choice of signing standard depends on the ecosystem and regulatory requirements.
When Level 3 Is Appropriate
Level 3 is appropriate when the law or business relationship requires explicit, provable consent:
- Regulated industries (financial services, healthcare, insurance)
- High-value contracts
- Agreements with specific legal requirements for signatures
- Cross-border agreements where consent must be independently verifiable
For transactions that additionally require hooks to legal infrastructure (dispute resolution, escrow, compliance), see Level 4: Integrated.