@node FAQ
@unnumbered Frequently Asked Questions

See also this page @ref{ЧАВО, on russian}.

@menu
* Why do not you use TLS?: Why not TLS.
* Why do not you use SSH?: Why not SSH.
* Why do not you use IPsec?: Why not IPsec.
* Why GoVPN is written on Go?: Why Go.
* Why do you authenticate with passphrases?: Why passphrases.
* Why all network configuration must be done manually?: Why manual network configuration.
* Why there is no either OS X or Windows support?: Why no proprietary OS support.
* What do you mean by perfect forward secrecy?: What is perfect forward secrecy.
* What do you mean by saying that clients are anonymous?: What is anonymity.
* What do you mean by censorship resistance?: What is censorship resistance.
* When should I use encryptionless mode?: When encryptionless mode.
* When should I use noise option?: When noise option.
* When should I use time synchronization option?: When timesync option.
* Can I DoS (denial of service) the daemon?: Can I DoS daemon.
* Why YAML for configuration?: Why YAML.
@end menu

@node Why not TLS
@section Why do not you use TLS?

@itemize
@item It is complicated badly designed protocol.
@item It uses Authenticate-then-Encrypt ordering of algorithms.
@item Its libraries are huge and hard to read, review and analyze.
@end itemize

@node Why not SSH
@section Why do not you use SSH?

@itemize
@item Its first protocol versions used A-a-E ordering, however later
ones supports even ChaCha20-Poly1305 algorithms.
@item OpenSSH does not support strong zero-knowledge password
authentication.
@end itemize

@node Why not IPsec
@section Why do not you use IPsec?

It lacks strong zero-knowledge password authentication and, again,
its code is hard to read.

@node Why Go
@section Why GoVPN is written on Go?

Go is very easy to read, review and support. It makes complex code
writing a harder task. It provides everything needed to the C language:
array bounds checking, garbage collection and concurrency primitives. It
provides lesser performance (however my setup on the notebook gives more
than 750 Mbps of throughput), but higher reliability and much fewer
lines of code.

@node Why passphrases
@section Why do you authenticate with passphrases?

Human is capable of memorizing rather long passphrases (not passwords):
100-200 characters, that gives ability to use it as a high-entropy key.
You need to trust only yourself, neither hardware token nor some other
storage device. It is convenient.

@node Why manual network configuration
@section Why all network configuration must be done manually?

Because there are so many use-cases and setups, so many various
protocols, that either I support all of them, or use complicated
protocol setups like PPP, or just give right of the choice to the
administrator. VPN is only just a layer, just like Ethernet cable.

@node Why no proprietary OS support
@section Why there is no either OS X or Windows support?

Any closed source proprietary systems do not give ability to control the
computer. You can not securely use cryptography-related stuff without
controlling the underlying computing device. Choose another operating
system.

@node What is perfect forward secrecy
@section What do you mean by perfect forward secrecy?

You can not decrypt previously saved traffic by compromising long-lived
keys. PFS property is per-session level: it won't protect from leaking
the session key from the memory.

@node What is anonymity
@section What do you mean by saying that clients are anonymous?

That third-party can not differentiate one client from another looking
at the traffic (transport and handshake).

@node What is censorship resistance
@section What do you mean by censorship resistance?

Unability to distinguish either is it GoVPN-traffic is passing by, or
just @code{cat /dev/urandom | nc somehost}. If you can not differentiate
one kind of traffic from another, then your only option is to forbid all
kinds of it.

@node When encryptionless mode
@section When should I use @ref{Encless, encryptionless mode}?

If you are operating under jurisdiction where courts can either sue you
for encryption usage or force you to somehow reveal you encryption
keys (however new session encryption keys are generated each session).
Those courts can not demand for authentication and signing keys in most
cases.

@strong{Do not} let mode's name to confuse you: it still provides
confidentiality and authenticity of transmitted data! But pay attention that
this mode is traffic and resource hungry and currently operate only in TCP
mode.

If anything that can not be read by anyone is considered encryption,
then encryptionless mode won't help you. Imagine that either you are
talking on another foreign language, or just use another date encoding
scheme.

@node When noise option
@section When should I use @ref{Noise, noise} option?

In most cases you won't need it without @ref{CPR, constant packer rate}
turned on. Without CPR and noise options GoVPN traffic (like TLS, IPsec,
SSH and other VPN protocols) leaks underlying interface's packets
timestamps and sizes. You can run traffic analysis and predict what is
going on in the network. With CPR option enabled you can tell either
somebody is online, or not -- nothing less, nothing more.

@node When timesync option
@section When should I use @ref{Timesync, time synchronization} option?

Without that option, if someone captured initial handshake packet from
the valid client, then it could repeat it and receive a handshake packet
as an answer from server. This can be used to detect if some user's
identity is known to server and that it is exactly GoVPN server.
Timesync option forces adding timestamps to each handshake packet
allowing only specified time window of packet validness. If you have got
more or less synchronized clocks between your clients and server, then
you can always use this option.

@node Can I DoS daemon
@section Can I DoS (denial of service) the daemon?

Each transport packet is authenticated first with the very fast UMAC
algorithm -- in most cases resource consumption of TCP/UDP layers will
be higher then UMAC verifying. Each handshake message is processed only
when an encrypted client's @ref{Identity, identity} is found: it uses
fast PRP without any entropy usage.

@node Why YAML
@section Why YAML for configuration?

There are not so many well-known formats that allow commenting, easy
editing by human (XML is not human friendly at all, JSON is more or
less). Probably the most useful feature is YAML's templates: it is very
convenient for storing many clients sharing the same options in the
configuration file.