## Session Integrity Lifecycle

The Session Integrity Lifecycle defines the complete journey of an event from creation to final verification. Every session begins with a genesis event initialized using the `GENESIS_HASH`, establishing the foundation of the chain. As new events are generated, each event receives a sequential identifier and references the hash of its predecessor through the `prev_hash` field.

Before storage, events undergo JCS canonicalization and SHA-256 hashing to produce deterministic representations independent of formatting differences. Optional Ed25519 signatures may be attached for stronger authenticity guarantees.

During ingestion, the Ingestion Service independently recomputes event hashes, validates sequence continuity, and verifies structural correctness. Any inconsistencies trigger explicit failure events rather than silent repair mechanisms.

If all integrity checks succeed, a `CHAIN_SEAL` event is generated and appended to the session. This process establishes an independently verifiable record and upgrades the evidence classification according to system rules.

The lifecycle ensures traceability, cryptographic integrity, and independent verification throughout the complete event chain.

(README §How It Works; TRUST_MODEL §4)

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## Threat Model Overview

The Threat Model Overview defines the assumptions and adversarial conditions under which the system operates securely. The architecture is designed to defend against both accidental failures and intentional attempts to manipulate event history.

Potential attacks include:

- Event deletion
- Event insertion
- Sequence number manipulation
- Event replay attacks
- Partial chain corruption
- Full chain rewrite attempts
- Client-side log tampering
- Unauthorized event fabrication

Hash chaining prevents unnoticed structural changes by linking every event to its predecessor. Optional Ed25519 signatures protect against unauthorized chain recreation because attackers cannot forge signatures without possession of the session-specific private key.

Independent verification performed by the Ingestion Service adds an additional layer of trust by validating evidence outside the originating environment.

Security guarantees vary according to the resulting evidence class and corresponding trust assumptions.

(TRUST_MODEL §1; README §Evidence Classes)

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## Audit Transparency Principles

Audit Transparency Principles establish the philosophy that systems should communicate their limitations explicitly rather than imply guarantees they cannot prove.

Verifier outputs include a structured `trust_assumptions` block that records both validated and unvalidated properties of a session. Examples include:

- `byzantine_server_defended: false`
- `session_freshness_verified: false`
- `instrumentation_complete: unknown`

These assumptions are intentionally fixed and not user configurable. This design prevents systems from overstating trust guarantees or hiding uncertainty.

Transparency allows auditors and users to accurately interpret evidence strength while understanding system boundaries.

The governing principle is:

"A system that does not disclose its limitations cannot be considered fully trustworthy."

(TRUST_MODEL §6; README §Evidence Classes)

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## Future Security Enhancements

Future versions of the architecture may introduce stronger verification and reduced trust assumptions through additional mechanisms.

Potential enhancements include:

- Byzantine fault tolerant ingestion services
- Distributed witness verification
- Transparency log integration
- Decentralized timestamp authorities
- Multi-party chain validation
- Hardware-backed attestation systems
- Session freshness verification improvements
- Cross-server integrity consensus

These additions aim to strengthen independent validation and reduce reliance on centralized trust assumptions.

Future improvements focus on making integrity verification increasingly resistant to both operational failures and malicious adversaries.

(README Future Work; TRUST_MODEL)
