Usage
=====
Nyaruko is a binary to text filter.  Given some input on stdin,
Nyaruko will produce C code that reproduces this input on stdout:

    ./nyaruko < original.bin > output.c
    gcc output.c -o output
    ./output > regenerated.bin

Output is encrypted, but both key and data are included in the output.
To separate the key from the data, run these commands:

    bash output.c > key.c
    perl output.c > data.c

The key-less data.c still compiles, but produces a different message
on stdout instead of the original input.  This message is a hint to
why the code is formatted the way it is.

To combine the key and data, concatenate them together in either
order:

    cat key.c data.c > output.c
    cat data.c key.c > output.c

By default, Nyaruko generates a unique random key for every message,
using /dev/urandom as the seed.  If given an extra command line
argument, Nyaruko will seed using that file instead of /dev/urandom:

    ./nyaruko seed.txt < input.bin > output.c

This makes the output key deterministic, allowing the same key to be
shared across different files.  On operating systems that do not have
/dev/urandom, users should always specify this extra seed argument to
avoid deterministic keys.


Features
========
Implementation details that makes Nyaruko more obfuscated than usual
programs:

   * Nyaruko recycles variables and buffers to reduce internal state.
     The variable names are also carefully chosen for mixed-case
     madness.
   * Nyaruko employs some preprocessor magic to share much of the same
     code and state between the encoder and decoder, and to increase
     occurrences of smileys ;)

Output code has these features:

   * Fits nicely under 80 columns, and does not contain any trigraphs.
   * Uses a fairly efficient encoding scheme, better than base64 for
     files larger than 20K.
   * Trivial 3 language polyglot.

Code layout is meant to resemble Nyaruko, also known as Nyarlathotep,
the Crawling Chaos.  The most obvious thing to do with chaos is to
make a random number generator, and the most obvious thing to do with
a random number generator is to make one-time-pads for encryption.
Actually Nyaruko implements the ISAAC pseudorandom number generator,
which as of 2012 has not been shown to have any bias.


Compatibility
=============
Nyaruko has these environment dependencies:

   * Requires ASCII character set.
   * Assumes sizeof(unsigned int) == 4.
   * Best viewed with tab stops set to 8 spaces.

Output code has the same dependencies, with the additional
requirement that the compiler must support string literals of
arbitrary length.

Nyaruko has been to verified to work with these compiler/OS
combinations:

   * gcc 4.4.5 on Linux (32bit and 64bit)
   * clang 3.1 on Windows (Cygwin)
   * gcc 4.5.3 on Windows (Cygwin)
   * gcc 4.5.3 on Windows (MingW)

Note that on MingW, stdin and stdout are not opened in binary mode by
default, this means Nyaruko may not faithfully encode files on MingW.


Extra files
===========
nyaruko.c - The submitted prog.c has spaces compressed to tabs to stay
under the 4K limit.  This is the original version with tabs expanded.

spoiler.html.gz - Contains full recording of how the code went from
blank state to an obfuscated program, gzipped to fit under 1MB.