HNBPv3: Context-Bound Witness Logs

HNBPv3 is a tamper-evident, append-only log format for people, devices and automated agents. Every hash input is length-prefixed and labelled; each log fixes one authentication tier and its identity in its first link. Tier U is a plain hash chain; tier P uses RFC 8391 XMSS signatures whose one-time keys are taken from true-random pad bytes and erased as used; tier M uses one-time Poly1305 keys from a shared pad and authenticates every field with no computational assumption. In every tier the authenticated message covers the log identifier, the record position and its predecessor, so a genuine proof cannot be moved. Supersedes HNBPv2, whose signature did not bind to content. Reference implementation checked against BouncyCastle, OpenSSL, the RFC 8439 vector and the Certificate Transparency test data; two independent implementations reproduced every vector.