Crate malt 

MALT

Merkle Append-Only Log Tree conforming to RFC 9162 §2.1.

This crate provides a generic, append-only Merkle tree parameterized by a TreeHasher trait. It supports incremental construction, root extraction, inclusion proofs, and consistency proofs.

The tree has zero external dependencies — callers provide their own hash implementation via TreeHasher.

Usage

use malt::{Log, TreeHasher};

// Implement TreeHasher for your hash function, then:
let mut log = Log::new(my_hasher);
log.append(b"first entry");
log.append(b"second entry");
let root = log.root();

Panic Policy

This crate uses expect() in two locations where the stack state is guaranteed by structural invariants:

• Log::append — merge pops are bounded by count_trailing_ones(size), which guarantees sufficient stack depth by construction (A-STACK).
• Log::root — fold over a non-empty stack (guarded by size > 0).

These are not input-validation panics. They guard invariants proven correct by the formal model (§3.4 A-STACK, A-EQUIV). Converting them to Result would impose API ergonomic cost for genuinely impossible errors.

Structs

ConsistencyProof

Consistency proof — proves a tree of old_size is a prefix of new_size.

InclusionProof

Inclusion proof — proves a leaf at index exists in a tree of tree_size.

Log

A dense, append-only, left-filled Merkle tree (RFC 9162 §2.1).

Enums

Error

Errors produced by MALT operations.

Traits

TreeHasher

Hash abstraction for the Merkle tree.

Functions

verify_consistency

Verify a consistency proof (formal model §5.3).

verify_inclusion

Verify an inclusion proof (formal model §4.3).