ioccc/2004/sds

Best Abuse of Indentation

Stephen Sykes Laivalahdenportti 2 00810 Helsinki Finland https://web.archive.org/web/20160316092728/http://www.stephensykes.com/

To build:

make

To run:

./sds

Try:

./sds < sds.c > encoder.c
make encoder
./encoder README.md <sds.c >sds_msg.c
make sds_msg
./sds_msg < sds.c > sds2_msg.c
diff sds2_msg.c encoder.c

Also try:

echo 'Hello, World!' > message
./encoder message < README.md > remarks.md
diff remarks.md README.md # notice how similar they are

# and then observe:
./sds < remarks.md

INABIAF - it's not a bug it's a feature! :-)

The generated code will very likely crash or do something else if not given a proper command line. This is not a bug but a feature.

Judges' remarks:

Why not use the program to hide another program in the program? It must have seemed reasonable at the time.

The ability to hide a message in plain text is quite charming, really. We must admit to a bit of uncertainty about where you'd find such messages, or how useful they'd be. Or, of course, whether all those horribly badly formatted emails spammers send might contain secret messages. Annoyingly, it's a little too obvious that SOMETHING has been done to a message for us to hide one in the remarks. :)

Author's remarks:

Stenography is the term for the family of techniques used for hiding information within other information. Today, it has many real world uses, particularly for digital watermarking.

This program uses a stenographic technique to hide information in any text file. The specific technique used is aimed at writers of obfuscated programs for the IOCCC, as the hidden information is encoded in the whitespace in the source file. As we know, there are up to an additional 2048 characters of whitespace available to entrants to the IOCCC, so it turns out that this is an ideal place to hide things.

The program as provided is the stenographic decoder. Rather than provide a separate encoding program, you should not be surprised to learn that I opted to stenographically hide the encoder inside the decoder.

Try it out. Compile the program, then type

sds < sds.c

You should see the encoder program displayed. Now save it, like:

sds < sds.c > encoder.c

Then compile encoder.c. You now have the complete system ready.

The encoder expects to get a filename as an argument. This filename is the name of the file containing the information to be hidden. It expects the file in which to hide the information to be on the standard input, and will output the results on the standard output.

You can use it like this (assuming you have a file called remarks):

echo 'Hello, World!' > message
./encoder message < remarks > remarks_msg

Then to decode:

./sds < remarks_msg
Hello, World!

C programs are mostly unaffected by adding steganographic content, but it is possible in certain circumstances for whitespace to be changed inside strings where it should be left alone. Plain text files are good candidates for hiding information in, but the added spacing may render the text somewhat difficult to read.

Obfuscation

This program is obfuscated in a number of ways:

• The code is all but impossible to read due to the spacing.
• The algorithm is well hidden in the code due to copious red-herrings.
• The long expressions cause indentation tools to give poor results.
• And good old fashioned ternary operators are the icing on the cake.

Compiling the program

The program (and the encoder program) should compile on any reasonable compiler. In particular, they are known to compile under GNU C.

Copyright and CC BY-SA 4.0 License:

This file is Copyright (c) 2023 by Landon Curt Noll. All Rights Reserved. You are free to share and adapt this file under the terms of this license:

Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)

For more information, see: https://creativecommons.org/licenses/by-sa/4.0/