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Highly secure isolated air-gap computers ¶

If you worry much about security, then air-gapped computer could be the only choice you can afford. Computer without any modems, wired and wireless networks. Obviously the only possibility to exchange mail and files is to use physically removable storage devices like CD-ROM, hard drive, SD, tape and USB flash drives (worst choice, due to those devices complexity).

Presumably you have got another own hop before that computer: another intermediate node which performs basic verification of retrieved storage devices, possibly by rewriting the data from USB/hard drives to CD-RWs.

NNCP supports packets relying (transitioning) out-of-box.

neigh: {
  bob: {
    [...]
    addrs: {
      lan: "[fe80::5400%igb0]:5400"
    }
  }
  bob-airgap:
    [...]
    via: ["bob"]
  }
}

That configuration file tells that we have got two known neighbours: bob and bob-airgap. bob can be reached via online connection using lan address. bob-airgap can be reached by sending intermediate relay packet through the bob.

Any command like nncp-file myfile bob-airgap: will automatically create an encapsulated packet: one for the destination endpoint, and other carrying it for intermediate relaying node.

Pay attention that relaying node knows nothing about the packet inside, but just its size and priority. Transition packets are encrypted too: using well-known onion encryption technology. bob can not read bob-airgap’s packets.