# Most Obfuscaed Audio
Aaron Grothe
2205 South 51st Street
Omaha, NE 68106
US
## Judges' Comments:
### To build:
make grothe
### To run:
./grothe 65000000 10000000 1344 < twinkle.txt
... and then put on your "electronic ears". You may find using
a tunable scanning electronic ear helps.
Most of the time, interference is annoying. This entry is the
exception that proves the rule. What is a bug to some is a
feature to this entry. :-)
## Selected Author's Comments:
The program draws patterns on the screen that can be picked up by a
shortwave radio. It emulates the frequencies for an old fashion touch
tone phone, so old songs can be played by hitting 0-9,#, and *.
To be able to run the program you need to determine the following
parameters
carrier_freq - base frequency used to host music
pixelclock - refresh rate of the monitor
horizontal_total - total scan along the horizontal axis
If you have xvidtune installed you can get the pixelclock and
horizontal total with the following command
xvidtune -show | head -n 1 |
awk '{ print "pixelclock " $2 * 1000000 " horizontal_total = " $6 }'
example from my laptops
./grothe 65000000 10000000 1344 < twinkle.txt
Even if the user gets a setting off, the sound will usually be able to be
heard on AM at a multiple of the original frequency
The core idea of using a machine to play music on AM radio goes all the
way back to the Altair computers and Timex Sinclair ZX-81s.
### Several example songs
Olympic Fanfare - from antang@phakt.usc.edu - Tony
4-9-91231,2222-321123123-9-91231,2222-32112321
Twinkle Twinkle Little Star - from fsufunkyb@aol.com - Ben Schmidt
1199##9-6633221-9966332-9966332-1199#9-6633221-
Generic Arabian Tune - from rdippold@qualcomm.com -Ron "Asbestos" Dippold
453,54,4569564459,9#95458,8987453 54
Others can be found by doing a search for "touch tone phone songs".
### Obfuscations
- Some numbers expressed in Octal, some in hex and some in decimal
"A foolish consistency is the hobgoblin of little minds" -
Ralph Waldo Emerson
- Funky scoping, looking at the nanosleep section and
XsetWindowAttributes declares local variables
- Algorithm is very weird, uses y dimension to draw carrier frequency
and x dimension to draw audio frequency, based on Erik Thiele's
Tempest for Eliza
- lack of #defines confuses many people :-)
- figuring out your pixelclock and horizontal total and which carrier
frequency to use can be an exercise in obfuscation for the user
- use of commas in various places, confuses most c code beautifiers
sometimes making the beautified code harder to read
- use of static to ensure initilization is EVIL and done in several
places
- uses static declarations & voids function returns we don't care about
making the code harder to read
- does sound using only X11 libs, no other libs required
- demonstrates tempest emissions in a fun/easy way
- follows good programming practices of actually setting exit codes and
giving usage when run with incorrect parameters
### References
Tempest for Eliza - Basis for Algorithms
>
Tempest AM - Another early program in this field
>
Paper by Markus G. Kuhn's and Ross J. Anderson's,
"Soft Tempest: Hidden Data Transmission Using Electromagnetic Emanations"
>