nwid:
{ pkgs, ... }:
let
  ztInterfaceScript = pkgs.writeShellScript "zt-interface" ''
    #!/usr/bin/env bash

    network="$1"
    index=${"2:-0"}

    network="0x$network"

    # zerotier hash function 
    network=$(( (($network ^ ($network >> (3*8))) + $index ) % (1<<(5*8)) ))

    # encode the result in base32
    while [ $network -gt 0 ]; do
      index=$(( $network % (1<<5) + 24 ))
      [ $index -lt 50 ] && index=$(( $index + 73 ))
      result="$(printf "\\%03o" $index)$result"
      network=$(( $network >> 5 ))
    done

    echo "zt$(printf %b "$result")"
  '';
  result = pkgs.runCommand "zt-interface-output" { } ''
    ${ztInterfaceScript} > $out
  '';
in
builtins.readFile result