# `EEVM.MPT.Trie`
[🔗](https://github.com/mw2000/eevm/blob/main/lib/eevm/mpt/trie.ex#L1)

Ethereum Merkle Patricia Trie (MPT) root computation.

The trie is path-compressed (nibble-by-nibble keys, hex-prefix compact
encoding for leaves and extensions) and content-addressed: each node is
RLP-encoded, and a child reference is either the raw RLP payload (when
`byte_size(RLP(node)) < 32`) or `keccak256(RLP(node))` otherwise.

Implements the recursive `patricialize` strategy from Ethereum's execution
specs, producing roots compatible with geth/revm for the same inputs.

# `entry`

```elixir
@type entry() :: {binary(), binary() | nil}
```

Raw trie key bytes and value bytes (nil means deletion in sequential updates).

# `nibble`

```elixir
@type nibble() :: 0..15
```

Nibble values used for trie paths.

# `node_ref`

```elixir
@type node_ref() :: {:raw, binary()} | binary()
```

# `trie_node`

```elixir
@type trie_node() ::
  nil
  | {:leaf, [nibble()], binary()}
  | {:extension, [nibble()], trie_node()}
  | {:branch, %{optional(nibble()) =&gt; trie_node()}, binary() | nil}
```

# `root_hash`

```elixir
@spec root_hash([entry()]) :: binary()
```

Computes the MPT root hash from `{key, value}` pairs.

Keys are inserted as-is (non-secure trie). Entries are applied sequentially;
if a key appears multiple times, later values overwrite earlier ones. A `nil`
value deletes the key.

# `secure_root_hash`

```elixir
@spec secure_root_hash([entry()]) :: binary()
```

Computes the secure-trie MPT root hash.

Secure tries pre-hash each key with Keccak-256 before insertion.

---

*Consult [api-reference.md](api-reference.md) for complete listing*