Serialization and tries

The three encodings the protocol commits to, and the helpers built on them. RLP (YP Appendix B) is the wire and trie encoding of protocol structures; SSZ frames the stateless input envelope; the Merkle-Patricia trie (YP Appendix D) turns key–value state into the roots the header commits to.

• Contract address derivation and transaction signature rules — shared helpers over the primitive types.
• RLP — encoding, decoding, and transaction envelopes.
• SSZ — decoding the witness envelope.
• SSZ hash_tree_root — the Merkleization of the stateless input.
• Merkle Patricia Trie — paths, nodes, updates, and the witness-native walker.
• State trie — accounts and storage over the trie, producing the post-state root.