> ## Documentation Index
> Fetch the complete documentation index at: https://docs.qedproof.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Merkle log

> The append-only, RFC 6962-style log every receipt is written into.

Every receipt QED Proof issues is appended to a Merkle tree log, in the style of RFC 6962 (the Certificate
Transparency log format). This is what makes a receipt checkable independent of QED Proof's own database: instead of
trusting an API response, you verify that a receipt is included in a tree whose root is public.

## Leaves

Each receipt becomes one leaf:

```
leaf_hash = SHA-256( 0x00 || JCS({ "body": body, "signature": signature }) )
```

Interior nodes are `SHA-256( 0x01 || left || right )`. The `0x00` / `0x01` prefixes on leaves and interior nodes
follow RFC 6962, and stop a leaf hash from ever being reinterpreted as an interior node hash (or vice versa).

The log is append-only by construction — QED Proof's storage refuses updates and deletes against receipts, leaves,
and roots.

## The `proof` object

A receipt's `proof` carries what you need to check inclusion:

```json theme={null}
"proof": {
  "log_id": "<base64url>",
  "leaf_index": 88213,
  "tree_size": 88240,
  "root_hash": "<base64url>",
  "inclusion": ["<base64url>", "..."],
  "anchor": { "..." }
}
```

To check inclusion, recompute `leaf_hash` from the receipt's own `body` and `signature`, then run the RFC 6962
audit-path verification using `leaf_index`, `tree_size`, and the hashes in `inclusion`. It must produce exactly
`root_hash`.

`anchor` may be absent — that happens at trust level 1, or at trust level 2 before an anchor has landed yet for this
part of the tree. An absent anchor is a limitation of the proof, not an invalid receipt. See
[anchoring](/concepts/anchoring) for what it adds, and [check a receipt](/concepts/check-a-receipt) for running this
verification yourself.