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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.

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Leaves

Each receipt becomes one leaf:
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.

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The proof object

A receipt’s proof carries what you need to check inclusion:
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 for what it adds, and check a receipt for running this verification yourself.