Thursday, December 8, 2011

iCTF 2011 Challenge 12 Writeup

Challenge 12 ($150)

Given the audio file "123.wav". When listening it, you will get a "silence" after the last phrase "... my price is ...".

But when you'll open a file in hex editor, you'll see a hint "Multiply the given price" at the offset 0x4E.

Open "123.wav" in any audio editor (e.g. Audacity) and get the frequency of "silence" sound after the last phrase. The frequency is equal to 21000 Hz. So using the hint, multiply file's name value by frequency value and get the answer.
Answer: 2583000

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