KERI (Key Event Receipt Infrastructure)

KERI uses Autonomic Identifiers (AIDs) that are cryptographically self-certifying. The identifier is derived directly from the inception key pair, meaning the identifier itself proves control of the private key without requiring a third-party registry lookup.

• Derivation: The AID is a cryptographic digest of the initial public key
• Self-verification: Anyone can verify the binding between the identifier and its controller by checking the signature
• No registration required: Unlike DIDs anchored to blockchains, AIDs establish trust purely through the key event log

The Key Event Log is an append-only, cryptographically chained sequence of events that records every key state change for an AID. Each event is signed by the current controlling key and references the previous event's digest.

• Tamper-evident: Any alteration to a prior event breaks the hash chain
• Self-contained: The entire history of key rotations and delegations exists within the log itself
• Portable: The KEL can be stored anywhere—a database, a file system, or replicated across witnesses—without dependency on any specific ledger

KERI mandates pre-rotation of keys: each key event must commit to the hash of the next key before that key is used. This prevents post-compromise attacks where an attacker who steals a current key could rewrite history.

• Forward security: Even if the current private key is compromised, the attacker cannot forge a valid prior rotation because the next key hash was already published
• Non-repudiable: The cryptographic commitment chain proves the legitimate controller authorized every state change
• Quantum-resistant readiness: The hash-based commitment structure provides a foundation for post-quantum key types

KERI employs a witness network—a set of designated nodes that receive and acknowledge copies of key events. Witnesses do not validate transactions or reach consensus; they simply serve as neutral observers to detect duplicity.

• Duplicity detection: If a controller signs two conflicting versions of the same event, witnesses can produce cryptographic proof of the equivocation
• Minimal trust: Witnesses cannot alter the KEL; they can only expose misbehavior
• Scalable: Unlike consensus validators, witnesses require no coordination overhead, enabling high throughput

KERI is fundamentally ledger-agnostic. The KEL provides its own verifiable data structure, so anchoring to a blockchain or distributed ledger is optional and used only for ambient verifiability, not as a source of truth.

• No gas fees: Operations do not require on-chain transactions
• No throughput limits: Key events process at network speed, not block time
• Optional anchoring: A digest of the KEL can be periodically anchored to any ledger for additional discoverability, but the KEL remains the authoritative record

KERI supports sophisticated key management structures including delegated identifiers and threshold multi-signature schemes. An AID can delegate signing authority to another identifier with explicit constraints.

• Hierarchical trust: Organizations can create subordinate identifiers with limited authority scoped to specific contexts
• M-of-N signing: Require multiple parties to authorize key rotations or credential issuances
• Recovery mechanisms: Designate recovery keys that can rotate compromised keys without losing control of the identifier