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Module leaf

metamorphic_log

Module leaf 

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Layer-0: canonical leaf encoding and content hashing.

A transparency-log leaf is opaque, app-defined record bytes. Layer 1 (the Merkle tree, crate::merkle) treats them as a byte string and never inspects their structure, so an application’s canonical record drops in as a leaf with zero reformatting.

This module provides:

  1. ContextLabel — the versioned <namespace>/<record-type>/v<N> domain separator used by the intra-chain content hash. Each application chooses its own namespace and record types (e.g. "acme/user-keys/v1", "example-app/audit-event/v2"). The label lives inside the content hash (it never touches Layer 1’s tile mechanics), giving cross-protocol / cross-context separation while keeping the Merkle layer label-agnostic (#299 / #290).

  2. content_hash — the generic intra-chain leaf-content hash, sha3_512_with_context(label, content) from metamorphic_crypto. This is the per-identity continuity linkage; it is independent from, and must not be confused with, the RFC 6962 Merkle leaf hash (crate::merkle::hash_leaf). The same leaf bytes feed both linkages without reformatting either.

  3. key_history_v1 — a worked, byte-exact example/conformance instance of an application record type. It is not privileged by the engine; it is simply the first real-world consumer’s leaf shape (Mosslet’s signed key-history, assets/js/crypto/key_history.js, locked by test/mosslet/crypto/key_history_test.exs) and the seed of the cross-language KAT suite (#315 / #299). Any other application defines its own record type the same way, against this same fixed byte discipline.

§Byte-layout discipline (fixed, audited — version-bump-or-nothing)

All canonical encodings in this crate use a single, fixed discipline so that independent witnesses and cross-language SDKs recompute byte-for-byte:

  • integers are big-endian (u32 / u64),
  • variable-length fields are u32-be length-prefixed (lp(x) = u32_be(len(x)) || x),
  • the layout is never reordered; a change is a new version label, never a silent reinterpretation.

Modules§

key_history_v1
Example record type: the mosslet/key-history/v1 conformance instance.

Structs§

ContextLabel
A validated, versioned context label of the form <namespace>/<record-type>/v<N>.

Functions§

content_hash
Generic intra-chain leaf-content hash: sha3_512_with_context(label, content) (64 bytes).