@node Use cases
@unnumbered Use cases
+See also this page @ref{Сценарии, on russian}.
+
@menu
* Occasional connection to mail server: UsecaseMail.
+* Lightweight fast POP3/IMAP4 replacement: UsecasePOP.
* Unreliable/expensive communication link: UsecaseUnreliable.
* Slow/expensive link for high-volume data, bad QoS: UsecaseQoS.
* Extreme terrestrial environments, no link: UsecaseNoLink.
-* Private, isolated MitM-resistant networks: UsecaseF2F.
+* One-way broadcasting communications: UsecaseBroadcast.
+* Private, isolated MitM/Sybil-resistant networks: UsecaseF2F.
* Highly secure isolated air-gap computers: UsecaseAirgap.
-* Network censorship bypassing: UsecaseCensor.
+* Network censorship bypassing, health: UsecaseCensor.
* Reconnaissance, spying, intelligence, covert agents: UsecaseSpy.
@end menu
yet. Also you must have secure link (SSH, VPN, etc).
Another possibility is to use POP3/IMAP4 servers, but this is too
-overcomplicated and bloated for the simple task. Not an option. KISS!
+overcomplicated and bloated for the simple task. Not an option.
+@url{https://en.wikipedia.org/wiki/KISS_principle, KISS}!
Just tell both of your Postfixes (on the server and notebook) to drop
-email as a mail via NNCP (@ref{nncp-mail}) to specified node. This is
+email as a mail via NNCP (@ref{nncp-exec}) to specified node. This is
done similarly as with UUCP and as written in
@url{http://www.postfix.org/UUCP_README.html, Postfix documentation}.
will call local @command{sendmail} command to deliver them just like
that happened on the same machine.
+@node UsecasePOP
+@section Lightweight fast POP3/IMAP4 replacement
+
+@ref{nncp-daemon} can be connected with @ref{nncp-caller} for a long
+time -- it can create TCP connection that lasts for many hours. When
+SMTP server receives mail, it will call @ref{nncp-exec} creating an
+outbound encrypted packet. Daemon checks outbound directory each second
+and immediately sends notification about undelivered packets to remote
+side, that also downloads it at once.
+
+There are only dozens of bytes notifying about incoming packets, dozens
+of bytes telling to download those packets. Mail packets are compressed
+(POP3 and IMAP4 as a rule do not). You have lightweight, compressed,
+low-delay, reliable link for the mail with strong encryption and mutual
+sides authentication!
+
@node UsecaseUnreliable
@section Unreliable/expensive communication link
messages is problematic to retrieve. Moreover, each disconnect leads to
the same data retransmission again, that can not be afforded sometimes.
-Just send your @ref{nncp-mail, mail} and @ref{nncp-file, files} through
+Just send your @ref{nncp-exec, mail} and @ref{nncp-file, files} through
NNCP. You can use either offline delivery methods -- read about them in
the next section, or you can use included NNCP @ref{nncp-daemon, TCP
daemon}.
% nncp-file another_file bob:movie.avi
@end verbatim
-will queue two files for sending to @code{emph} node. Fire and forget!
-Now this is daemon's job (or offline transfer) to send this file part by
-part to remote system when it is available.
+will queue two files for sending to @emph{bob} node. Fire and forget!
+Now this is daemon's job (or offline transfer) to send this files part
+by part to remote system when it is available.
@node UsecaseQoS
@section Slow/expensive link for high-volume data, bad QoS
[...]
@end verbatim
+Huge files could be split on smaller @ref{Chunked, chunks}, giving
+possibility to transfer virtually any volumes using small capacity
+storages.
+
+You can also use CD-ROM and tape drives:
+
+@verbatim
+% nncp-bundle -tx bob | cdrecord -tao -
+% nncp-bundle -tx bob | dd of=/dev/sa0 bs=10240
+@end verbatim
+
@node UsecaseNoLink
@section Extreme terrestrial environments, no link
media for transferring packets to other nodes.
Assume that you send two files to @emph{bob} node. Insert USB storage
-device, mount it and run @ref{nncp-xfer}:
+device (SD is preferable!), mount it and run @ref{nncp-xfer}:
@verbatim
% nncp-xfer -node bob /media/usbstick
@end verbatim
-to copy all outbound packets related to @emph{bob}'s node. Use
-@option{-force} option to forcefully create related directory on USB
-storage if they are missing (for example when running for the first
-time).
+to copy all outbound packets related to @emph{bob}. Use @option{-mkdir}
+option to create related directory on USB/SD storage if they are missing
+(for example when running for the first time).
If you use single storage device to transfer data both to @emph{bob} and
-@emph{alice}, then just omit @option{-node} option to copy all existing
-outgoing packets to that storage device.
+@emph{alice}, then just omit @option{-node} option to copy all available
+outgoing packets.
@verbatim
% nncp-xfer /media/usbstick
@end verbatim
-Unmount it and transfer somehow to Bob and Alice. When they will insert
+Unmount it and transfer storage to Bob and Alice. When they will insert
it in their computers, they will use exactly the same command:
@verbatim
@end verbatim
to find all packets related to their node and copy them locally for
-further processing. nncp-xfer is the only command used with removable
-devices.
+further processing. @command{nncp-xfer} is the only command used with
+removable devices.
+
+@node UsecaseBroadcast
+@section One-way broadcasting communications
+
+Sometimes you have got high-bandwidth but unidirectional link, for
+example, satellite's broadcasting signal. You are not able to use online
+@ref{Sync, synchronization protocol} because it requires mutual interaction.
+
+You can use @ref{Bundles, bundles} and stream them above. They are just
+a sequence of @ref{Encrypted, encrypted packets} you can catch on.
+
+@verbatim
+% nncp-bundle -tx alice bob eve ... | command to send broadcast
+% command to receive broadcast | nncp-bundle -rx
+@end verbatim
+
+With built-in packet duplicates detection ability, you can retransmit
+your broadcasts from time to time, to increase chances the recipient
+will catch them by regular stream listening.
@node UsecaseF2F
-@section Private, isolated MitM-resistant networks
+@section Private, isolated MitM/Sybil-resistant networks
All Internet connections can be eavesdropped and forged. You
@strong{have to} to use encryption and authentication for securing them.
The most popular cryptographic protocol in Internet is
@url{https://en.wikipedia.org/wiki/Transport_Layer_Security, TLS} that
-is very hard to implement right and hard to configure for mutual
+is very hard to implement correctly and hard to configure for mutual
participants authentication. Not all TLS configurations and related
protocols provide @url{https://en.wikipedia.org/wiki/Forward_secrecy,
forward secrecy} property -- all previously intercepted packets could be
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, tape and USB flash drives (worst choice, due to those devices
-complexity).
+drive, SD, tape and USB flash drives (@strong{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
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.
-@emph{bob} can not read @emph{bob-airgap}'s packets.
+but just its size and priority. Transition packets are encrypted too:
+using well-known @url{https://en.wikipedia.org/wiki/Onion_routing, onion
+routing} technology. @emph{bob} can not read @emph{bob-airgap}'s packets.
@node UsecaseCensor
-@section Network censorship bypassing
+@section Network censorship bypassing, health
This is some kind of bad link too. Some governments tend to forbid
@strong{any} kind of private communication between people, allowing only
entertainment content delivering and popular social networks access
(that are already bloated with advertisements, locally executed
-proprietary JavaScript code (for spying on user activities, collect data
-on them), shamelessly exploiting the very basic human need of communication).
+@url{https://www.gnu.org/philosophy/free-sw.html, proprietary}
+JavaScript code (for spying on user activities, collect data on them),
+shamelessly exploiting the very basic human need of communication).
This is their natural wish. But nobody forces you to obey huge
corporations like Apple, Google or Microsoft. It is your choice to
Those guys know how Internet is a dangerous place incompatible with
privacy. They require quick, fast dropping and picking of data. No
possibility of many round-trips -- just drop the data, fire-and-forget.
-It could be either removable media again, or
-@url{https://en.wikipedia.org/wiki/USB_dead_drop, USB dead drops}, or
-@url{https://en.wikipedia.org/wiki/PirateBox, PirateBox}es, or
+It could be either removable media again and/or
+@url{https://en.wikipedia.org/wiki/USB_dead_drop, USB dead drops},
+@url{https://en.wikipedia.org/wiki/PirateBox, PirateBox}es,
@url{https://en.wikipedia.org/wiki/Short-range_agent_communications, SRAC}.
Short lived short range networks like Bluetooth and WiFi can also
be pretty fast, allowing to quickly fire chunks of queued packets.
@ref{Encrypted, encrypted} (but unfortunately lacking forward secrecy).
No filenames, mail recipients are seen.
-All communications are done with so-called @ref{Spool, spool} area:
+All node communications are done with so-called @ref{Spool, spool} area:
directory containing only those unprocessed encrypted packets. After
packet transfer you still can not read any of them: you have to run
another stage: @ref{nncp-toss, tossing}, that involves your private
with it (don't you?), you do not "toss" those packets immediately on the
same device. Tossing (reading those encrypted packets and extracting
transferred files and mail messages) could and should be done on a
-separate computer.
+separate computer (@ref{nncp-cfgmin} command could help creating
+configuration file without private keys for that purpose).