TinyMerkleTree Circom Proof Circuit

A zero-knowledge circuit in Circom to verify Merkle proofs generated from TinyMerkleTree. This circuit allows proving inclusion of a leaf in a tree without revealing other leaves.

Features

• Verifies a Merkle proof from TinyMerkleTree.
• Fixed depth trees (DEPTH configurable).
• Poseidon-based hashing for ZK compatibility.
• Efficient circuit size for verification.
• TypeScript-friendly for proof generation and verification.

Merkle Proof Concept

To prove that a leaf L is in the tree with root R:

1. Provide the leaf value L (private)
2. Provide sibling hashes along the path (pathElements)
3. Provide left/right indices for each sibling (pathIndices)
4. Circuit recomputes hashes up to the root and asserts it equals R

Example Depth 3:

Leaf: L2
Proof Path: [H3, H1]
Root: H7

Circuit recomputes:
hash(L2, H3) -> H6
hash(H6, H1) -> H7'
Assert H7' == H7

Circuit Interface

Inputs

Name	Type	Description
leaf	private	Leaf being proven
pathElements	private	Sibling hashes along the path
pathIndices	private	Left/right indices (0/1)
root	public	Merkle root to verify against

Constraints

• Hash function: Poseidon (PoseidonT2 for two inputs)
• Depth: Fixed, must match TinyMerkleTree depth
• Computation is incremental from leaf → root
• Public output: boolean equality check computedRoot == root

Notes

• Ensure circuit depth matches TinyMerkleTree depth
• Use Poseidon hash in the circuit identical to your tree
• Circuits scale logarithmically with depth; depth 32 is manageable
• Private inputs: leaf, pathElements
• Public input: root

License

MIT