Structured Pad Geometry: Multi-Channel Partitioning, Sequence-Indexed Addressing, and Pure-Tier Media over a Single One-Time Pad

Abstract

A shared one-time pad is conventionally treated as a single linear byte stream consumed front to back, one message after another. This wastes the pad's structural potential, forces a single serialised channel, and leaves the pad's most dangerous failure — reuse of bytes across two messages — as a discipline the implementer must never once violate. It also makes reception fragile: a running receive cursor desynchronises permanently the first time a message is lost, reordered, or duplicated, which on a public relay is the normal case rather than an edge case. We present a complete organising layer for a single pad, in three parts that turn out to be one design. First, a deterministic geometry: the pad is partitioned into typed, direction-split channels plus a reserve used only to derive rendezvous identifiers, as a pure function of pad length and endpoint role, so both sides compute identical layouts with no negotiation, and boundary guards convert reuse prevention from a runtime discipline into a structural invariant. Second, sequence-indexed addressing: each message's pad offset is a pure function of its sequence number rather than of the receiver's history, and a look-ahead window of expected identifiers replaces a single "next" identifier, so any message opens independently of whether its predecessors arrived. Third, pure-tier media: because the geometry provides typed zones and the addressing provides out-of-order opening, images and voice can be carried at the same information-theoretic tier as text via a sealed manifest-and-blob pair, with media type, ephemerality flag, and blob coordinates all sealed. We give the layout function, the addressing scheme, a desync-immunity argument, the media construction, exact capacity semantics, and the honest costs of each. Keywords: one-time pad, keystream management, two-time-pad prevention, reorder tolerance, length hiding, metadata hiding, perfect secrecy, media encryption. ---