Write-up on RootBSD's forensics challenge

Saturday, RootBSD (@r00tbsd #hackbbs) organized a small forensics challenge (french). About 30 people played the challenge, and we had fun. Fellow Nibbles member sh4ka quickly took the first place in just 2 hours and therefore won a shirt of his choice at getdigital.de. I played with two friends - 0vercl0k and thaw - and we took second place a few minutes after sh4ka. Below is my write-up for all the flags, but other players have also posted their write-ups: m_101 and tryks.

smpCTF challenge #1 write-up

smpCTF challenge #1 was a simple web + programming challenge.

We were given the following instructions:

Set S = 1
Set P = 1
Set previous answer = 1

answer = S * P + previous answer + R
R = 39

After this => S + 1 and P + 1 ('answer' becomes 'previous answer') + 39
then repeat this till you have S = 11065.

The final key will be the value of 'answer' when S = 11065.

Example:
So if R = 15..

17 = 1 * 1 + 1 + 15
36 = 2 * 2 + 17 + 15
60 = 3 * 3 + 36 + 15

Submit the correct answer and you will recieve a flag. Have fun ;D