Balanced use of obfuscation - Gold award

Adar Zeitak
aa4z2@walla.co.il

Judges' comments:

To build:

make zeitak

To run:

./zeitak < file.c

where file.c is the file to be checked for nesting errors. For example, you may try incorrect.c and the program itself.

Try:

./zeitak < zeitak.c
./zeitak < incorrect.c

Selected Judges Remarks:

This is an extremely subtle and twisted piece of Gold award winning code!

The judges had spent a considerable amount of time analyzing this entry. At one point we spent 18 minutes just to understand 18 key characters of this code.

The file zeitak_deobfucate.c provides a version that has been slightly deobfuscated. You may find reading that file helpful in your attempt to understand this extremely subtle entry.

Author’s comments:

Nesting Errors Detector

What does it do

As you have probably understood by looking at the source*, this program has something to do with parenthesis (and equality of opening and closing parenthesis, if you look close enough). It goes over the file given to it and checks that every opening (, [, or { has a matching closing one and vice versa. It also checks that every “ or ‘ is closed.

If an error is detected, an error message will be printed. If the problem is a superfluous closing bracket, it will even print a few characters around it’s position.

Features

Mis-Features

Obfuscation

IOCCC winners already contain entries without digits, control-flow keywords and certain operators in their source. This entry has an even more limited source, that is:

So, what’s left? Parenthesis, and lots of them, as looking at the source will reveal immediately. The main obfuscation is building the whole algorithm using only function calls, typecasts, array lookups and pointer operators.

Additional obfuscations include:

Compilation/Running Notes

Ubuntu 9.04 32-bit with GCC Windows 7 32-bit with GCC ** Windows 7 32-bit with OpenWatcom


Creative Commons License

© Copyright 1984-2012, Leo Broukhis, Simon Cooper, Landon Curt Noll - All rights reserved
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.