Where the guarantee stopped

A subject the papers are about. The loosest grouping, and the one to reach for last.

Three guarantees that were sound and failed anyway, because the failure arrived exactly where each one stopped: data corrupted inside a gateway that checksummed every hop, an intruder who was an untrustworthy principal in a logic that analysed only trustworthy ones, and Byzantine tolerance whose assumption of independent failure cannot be priced once the nodes share an operating system. Each paper states its own boundary plainly; in each case the boundary, not the guarantee, is what was read carelessly.