DEFONEOS · SIGIL Ledger Specification

1. What Is SIGIL?

SIGIL (Sovereign Integrity Guard for Immutable Logging) is DEFONEOS's permanent audit trail. Every tool invocation, governance decision, data access, data release, and system event generates a SIGIL receipt. Each receipt is cryptographically signed, timestamped, and anchored to the Bitcoin blockchain — making the ledger tamper-evident and permanent.

Three cryptographic layers: (1) Ed25519 signature proves who acted. (2) RFC3161 timestamp proves when they acted. (3) Bitcoin OTS anchor proves the receipt existed at that time and has not been modified since.

2. SIGIL Receipt Structure

Every SIGIL receipt contains the following fields:

{ "sigil_id": "sig_0123_abc456...", // Ed25519-derived unique ID
"tick": 103, // Global tick counter
"action": "tool_invoke", // What happened
"mcp_id": "sentinel-hub-mcp", // Which MCP server
"tool_name": "get_satellite_image", // Which specific tool
"caller": "ed25519:0xABC...", // Who called it
"ring": 1, // Trust ring (0, 1, or 2)
"data_hash": "sha256:0xDEF...", // Hash of input + output
"timestamp": "2026-07-14T19:30:00Z", // ISO 8601
"rfc3161_receipt": "base64:...", // Trusted timestamp proof
"ots_proof": "bitcoin:block:850000...", // Bitcoin OTS anchor
"signature": "ed25519:0x123...", // Caller's signature
"bft_witness": "ed25519:0x456...", // BFT agent co-signature
"release_condition": null, // RC-1 to RC-6 (for data releases)
"metadata": {} // Action-specific context }

3. The Three Cryptographic Layers

Layer 1 — Ed25519 Signature (Who)

Every actor in DEFONEOS (human or AI) has an Ed25519 key pair. When an action is taken, the actor signs the SIGIL receipt with their private key. The signature proves who performed the action and that the receipt has not been modified since signing.

Key generation: Each actor generates their Ed25519 key pair on first registration.
Key rotation: Every 90 days, or immediately on compromise.
Key revocation: BFT council can revoke keys (Emergency Session P4).
Multi-signature: Data releases require 2 human signatures + 1 BFT witness signature.

Layer 2 — RFC3161 Trusted Timestamp (When)

Every receipt is timestamped by an RFC3161 Trusted Timestamp Authority (TSA). The TSA signs a hash of the receipt + the current time, proving when the receipt was created (to TSA-attested precision).

TSA: FreeTSA.org (free) or organisational TSA (self-hosted, UK-only).
Receipt format: ASN.1 DER-encoded TimeStampResp (RFC 3161 standard).
Verification: Receipt can be independently verified against the TSA's public key.
Anti-replay: The timestamp includes a nonce, preventing receipt reuse.

Layer 3 — Bitcoin OTS Anchor (Existed)

Every receipt is anchored to the Bitcoin blockchain via OpenTimestamps (OTS). This proves the receipt existed at a specific point in time and cannot be backdated or modified.

How it works: OTS takes the SHA-256 of the receipt, creates a Merkle path, and embeds the root hash in a Bitcoin transaction.
Cost: Free (OTS aggregates timestamps into shared Bitcoin transactions).
Verification: Anyone can verify the OTS proof against the Bitcoin blockchain — no trusted third party needed.
Permanence: As long as the Bitcoin blockchain exists (forever), the proof exists. This is the strongest possible timestamp guarantee.

4. Action Types Recorded

Action	Description	BFT Witness Required
`tool_invoke`	A tool was called on an MCP server	Yes (standard)
`bft_vote`	A BFT agent cast a vote	Self (the vote IS the witness)
`bft_session`	A BFT session (standard or emergency) completed	All participating agents
`data_store`	Data was stored in the escrow	Yes
`data_access`	Escrow data was accessed	Yes
`data_release`	Escrow data was released (RC-1 to RC-6)	Yes + 4-eyes + BFT quorum
`data_destroy`	Escrow data was cryptographically destroyed	Yes + 23/33 BFT + human-owner
`key_rotation`	An Ed25519 key was rotated	Yes
`mcp_admission`	An MCP was admitted to the federation	23/33 BFT quorum
`mcp_quarantine`	An MCP was quarantined	17/33 BFT emergency quorum
`redline_proximity`	An output approached a red-line boundary	Immediate emergency session
`deploy`	A new deployment was pushed to production	BFT pre-flight vote

5. Ledger Properties

Property	Value	How Enforced
Append-only	Receipts can never be modified or deleted	SQLite journal_mode=WAL + hash chaining + Bitcoin OTS
Tamper-evident	Any modification is immediately detectable	Ed25519 signature + RFC3161 timestamp + OTS anchor
Permanent	Receipts retained indefinitely	UK-sovereign storage + Bitcoin blockchain (OTS)
Verifiable	Anyone can independently verify receipts	Public Ed25519 keys + RFC3161 TSA public key + Bitcoin chain
Ordered	Receipts have a global tick ordering	Monotonic tick counter + RFC3161 timestamps
Complete	Every action generates a receipt	Architecture-level enforcement (no action path bypasses SIGIL)

6. Hash Chaining

SIGIL receipts are hash-chained: each receipt includes the hash of the previous receipt. This creates a tamper-evident chain where modifying any receipt breaks the chain for all subsequent receipts.

Receipt N-1 Receipt N Receipt N+1
┌──────────────┐ ┌──────────────┐ ┌──────────────┐
│ prev_hash: ∅ │ ────→ │ prev_hash: H(N-1)│ ────→ │ prev_hash: H(N) │
│ data: {...} │ │ data: {...} │ │ data: {...} │
│ hash: H(N-1) │ │ hash: H(N) │ │ hash: H(N+1) │
│ sig: ed25519 │ │ sig: ed25519 │ │ sig: ed25519 │
└──────────────┘ └──────────────┘ └──────────────┘

Modifying Receipt N changes H(N), which breaks Receipt N+1's prev_hash check → DETECTABLE

7. Verification API

The SIGIL ledger exposes a verification endpoint:

GET https://deploy.escrow.mcp/sigil/verify?sigil_id=sig_0123_abc...

Returns:

{ "sigil_id": "sig_0123_abc...", "ed25519_valid": true, "rfc3161_valid": true, "ots_valid": true, "hash_chain_valid": true, "overall": "VERIFIED" }

Bulk verification: GET /sigil/verify-all — verifies every receipt in the ledger. Used for periodic integrity audits.

8. Retention Policy

Data Type	Retention	Location
SIGIL receipts (all types)	Permanent	UK-sovereign SQLite + Bitcoin blockchain (OTS)
SIGIL receipts (BFT session transcripts)	7 years (full) / Permanent (minutes)	UK-sovereign storage + SIGIL ledger
SIGIL receipts (public-facing minutes)	Permanent	csoai.org/bft-minutes (OSA s7 redacted)
SIGIL verification proofs	Permanent	Bitcoin blockchain (immutable by design)

Even if all UK storage is destroyed, the Bitcoin OTS anchors remain, proving that the receipts existed at specific times. The receipts themselves can be reconstructed from the hash chain + backup copies.