Format-Preserving Tokenization Pipeline

Smart-data records — account numbers, smart-meter IDs, telemetry keys — stream through a 3D pipeline where each 8-digit value is split into a left and right half and pushed through a Feistel network, one round-function gate at a time. Switch between reversible Format-Preserving Encryption, which any holder of the round key can run backward to recover the exact original digits, and one-way hash tokenization, which a vault alone can reverse — then try detokenizing the last completed record with the correct key and with a guessed wrong one to see why key secrecy is the entire security model.