MPT Proofs

Merkle Patricia Tries (MPTs) are used to prove Ethereum account and storage data.

What is an MPT?

An MPT is a trie-based authenticated data structure with three node types:

• Branch: up to 16 children + value
• Extension: shared key prefix and next node
• Leaf: final key/value pair

Keys are nibbles derived from keccak256 of the original key.

Proof structure

An MPT proof is a list of encoded nodes from root to leaf. Verification:

1. Decode each node (RLP).
2. Traverse using the hashed key path.
3. Confirm the final value or non-inclusion marker.

HDP performs this verification twice:

• Account proof against the block state_root
• Storage proof against the account storage_root

Non-inclusion proofs

If a key does not exist, MPT proofs return the empty value (0x80) for the requested slot. The verifier checks this condition explicitly.

Implementation references

• src/verifiers/evm/account_verifier.cairo
• src/verifiers/evm/storage_item_verifier.cairo
• crates/hints/src/verifiers/mpt.rs