# Cryptography number question

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## 2 Replies - 2265 Views - Last Post: 13 October 2013 - 10:29 PM

### #1 blankwall

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# Cryptography number question

Posted 13 October 2013 - 01:41 PM

Going through an old capture the flag question and I am having trouble understanding the solution to this problem.
Here is the problem-

1 - Zombie Talk

Zombies got communication-problems because of their heterogeneity, so they defined a standard for their communication. We need to know how to decrypt their messages in order to successfully defeat them. Luckily, a friend of mine found one of those encrypted messages:

0x1be15dc
77676058612
03062372
676
0x9542
0x2546c9ec
02614610
0x3b3154e5a0a923ff

Hint: uppercase seems legit.

So these 8 10 and 16 digit numbers and need to be switched to 36 digit numbers. So the entire block of numbers would then look like this.

17 14 21 21 24
35 24 22 11 18 14 28
17 14 27 14
18 28
29 17 14
10 12 12 14 28 28
15 21 10 16
32 14 21 24 31 14 11 27 10 18 24 0

But the problem is I dont understand how this conversion happened. Does anyone have an explanation of how the first block of numbers was converted into the second block?

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## Replies To: Cryptography number question

### #2 macosxnerd101

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## Re: Cryptography number question

Posted 13 October 2013 - 02:06 PM

Moved to Computer Science. Please don't post help questions in the lounge.

The prefix 0x usually indicates a hexadecimal number in many programming languages. I'd be inclined to start there (note that I haven't run through it myself).

### #3 Dormilich

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## Re: Cryptography number question

Posted 13 October 2013 - 10:29 PM

Quote

Does anyone have an explanation of how the first block of numbers was converted into the second block?

using #3 as example (shorter):

676 (decimal)
676 % 36 = 28
floor(676/36) = 18
=> 676 = 18 * 36^1 + 28 * 36^0

numbers starting with 0x are hex and numbers starting with 0 are octal numbers.

This post has been edited by Dormilich: 13 October 2013 - 10:32 PM