Post-Quantum Packet Authentication for the Unheaded Protocol

This document specifies a post-quantum cryptographic (PQC) authentication mechanism for the Unheaded Protocol Foundation. It defines a multi-algorithm, dual-layer, tiered authentication architecture integrating three NIST PQC digital signature standards -- FIPS 205 (SLH-DSA), FIPS 204 (ML-DSA), and FIPS 206 (FN-DSA) -- plus two NIST PQC key-encapsulation mechanisms -- FIPS 203 (ML-KEM) and FIPS 207 (HQC) -- with the Monad wire format, Sophia BPF map dictionaries, and Wotan per-flow memory model. Layer 1 (Wire-Level, REQUIRED): Full PQC signatures are stored in Sophia BPF maps via a "signature-by-reference" scheme. The Monad register carries compact 12-byte references (SigRef, KeyRef, SeqNum, HashPfx). Shield verifies signatures at the network perimeter and strips Monad Hop-by-Hop headers at ingress -- internal kingdom traffic never carries PQC wire overhead. Layer 2 (Application-Level, OPTIONAL): User applications MAY define verification requirements in Sophia application policy dictionaries. After wire-level authentication succeeds, the application reads Wotan per-flow PQC state and matches it against its own policy. Four PQC compliance tiers -- NONE, STANDARD, ENHANCED, and SOVEREIGN -- are signaled via Kingdom Mode bits in the Monad flags byte.