02 — Terminology

Claim

A signed JSON document asserting that an event occurred. A claim contains a type, domain, subject, timestamp, optional metadata, and an Ed25519 signature. Claims are self-contained and independently verifiable.

Domain

The DNS domain of the organization issuing a claim (e.g., marketplace.example.com). The domain is the identity anchor — it controls the signing key and is responsible for the claims it signs.

Subject

A pseudonymous identifier for the participant referenced in a claim. Derived as SHA-256 or HMAC-SHA256 of {domain}:{externalUserId}. The same real-world person has different subject hashes on different domains by design.

Claim Type

A namespaced string identifying the kind of event. Core types use the mir. prefix (e.g., mir.transaction.completed, mir.account.verified). Extension types use a domain prefix with colon (e.g., shopify.com:loyalty.earned). Types are validated by format, not by a central registry.

Signing Key

An Ed25519 private key held by the domain. Used to produce the signature on each claim. Never published.

Public Key

The Ed25519 public key corresponding to a domain's signing key. Published via DNS TXT record or .well-known/mir.json endpoint. Used by verifiers to check claim signatures.

Key Fingerprint

The SHA-256 hash of the raw 32-byte Ed25519 public key, hex-encoded. Used to identify which key signed a claim when a domain has multiple active keys.

Canonical Form

The deterministic JSON serialization of a claim's payload (excluding the sig field). Keys sorted lexicographically, no whitespace, UTF-8 encoded. This is the exact byte string that is signed and verified.

Signature

An Ed25519 signature over the canonical form of the claim payload. Base64url-encoded (no padding) in the claim document. 64 bytes when decoded (86 characters encoded).

Registry

An optional service that indexes claims for discovery, provides independent timestamps, and serves as an availability layer. A registry is not a trust anchor — it cannot forge signatures and is not required for verification.

Verifier

Any party that checks a claim's signature against the domain's published public key. Verification is deterministic and can be performed offline once the public key is known.

Trust Boundary Classification

A categorization of claim types by scope:

• intra_system — Actions within a single platform's boundary.
• cross_system — Actions where value crosses trust boundaries.
• privileged — Enforcement or verification actions requiring elevated authority.