Chain-of-Custody Offline

What does chain-of-custody prove?

The chain-of-custody proves four key properties about governance:

• ■Continuity: No gaps in the sequence from POLICY_LOADED to final receipt
• ■Integrity: No receipt has been modified after signing
• ■Authority: All receipts signed by the governance boundary's key
• ■Ordering: Events occurred in the sequence recorded

How does hash-linking create custody?

Each receipt contains the hash of the previous receipt. This creates a chain where modifying any receipt breaks all subsequent links.

Receipt #1                Receipt #2                Receipt #3
┌──────────────────┐    ┌──────────────────┐    ┌──────────────────┐
│ counter: 1       │    │ counter: 2       │    │ counter: 3       │
│ event: LOADED    │    │ event: MEASURE   │    │ event: DRIFT     │
│ prev: 00000...   │───▶│ prev: abc12...   │───▶│ prev: def34...   │
│ this: abc12...   │    │ this: def34...   │    │ this: ghi56...   │
│ sig: [signed]    │    │ sig: [signed]    │    │ sig: [signed]    │
└──────────────────┘    └──────────────────┘    └──────────────────┘

If Receipt #2 is modified:
- Its this_receipt_hash changes
- Receipt #3's prev_receipt_hash no longer matches
- Chain validation fails at Receipt #3

What is the offline validation process?

A verifier can prove custody without network access using only the evidence bundle:

1. 1.Load receipts: Read all receipts from bundle in counter order
2. 2.First receipt: Verify prev_hash equals 64 zeros (genesis)
3. 3.Each receipt: Verify signature using boundary public key
4. 4.Chain link: Verify prev_hash equals previous receipt's this_hash
5. 5.Counter: Verify counter is previous + 1 (no gaps)
6. 6.Chain head: Verify final receipt matches chain_head declaration

Why can't this be faked?

Creating a false custody chain requires one of these, each of which is computationally infeasible or detectable:

What about clock manipulation?

Timestamps can be manipulated if the boundary system clock is compromised. The chain provides ordering guarantees regardless:

• ■Counter ordering: Proves sequence regardless of timestamps
• ■TSA tokens: External timestamp authority provides trusted time
• ■DEGRADED_LOCAL: Receipts without TSA are flagged, verifier notes this
• ■External anchors: Checkpoint to immutable stores bounds manipulation window

Frequently asked questions