HMTFTP: HKDF-Derived TFTP with Optional AEAD Protection (v0.7)

HMTFTP is a lightweight UDP file transfer protocol derived from TFTP. It preserves the TFTP transfer model (RRQ/WRQ, DATA, ACK, ERROR, and OACK option acknowledgment) and replaces text options with binary TLVs. HMTFTP defines optional AEAD protection for DATA payloads using HKDF-derived keys from a pre-shared key (PSK). This document describes transfer behavior, extension processing rules, key derivation, nonce construction, and operational guidance for experimental implementations intended to facilitate interoperability. This document requests IANA actions for a UDP service name/port and registries for TLV Types and Ciphersuites. Until assignment, TBD1 is used as the default UDP port value.