System 2 — device on an untrusted network (T4–T8)

[DavidCozens]

T4 server-auth TlsStream; T5 BlockStore store-and-forward over the baseline FatFS file; T6 Crc16Policy; T7 TimeQualitySd; T8 MetaSd sequenceId. Reasonably secure — suitable for a device targeted at SL2 systems or at CRA. Sub-issue of #1.