NNCP (Node to Node copy) is a collection of utilities simplifying
secure store-and-forward files, mail and commands exchanging.

This utilities are intended to help build up small size (dozens of
nodes) ad-hoc friend-to-friend (F2F) statically routed darknet
delay-tolerant networks for fire-and-forget secure reliable files, file
requests, Internet mail and commands transmission. All packets are
integrity checked, end-to-end encrypted (E2EE), explicitly authenticated
by known participants public keys. Onion encryption is applied to
relayed packets. Each node acts both as a client and server, can use
push and poll behaviour model. Also there is multicasting areas support.

Out-of-box offline sneakernet/floppynet, dead drops, sequential and
append-only CD-ROM/tape storages, air-gapped computers support. But
online TCP daemon with full-duplex resumable data transmission exists.

WWW: http://www.nncpgo.org/