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Posts Tagged ‘day 4’

HACKvent 2015: Day 4

07 Dec 2015
CTF: Hackvent 2015
Link to challenge: http://hackvent.hacking-lab.com
Date Completed: 07 December 2015

Challenge

Solution

At first I was convinced this was a Vigenere cipher but this is not the case.
After a clue from M from the hacking-lab IRC channel I was able to figure out the cipher used is the Scytale cipher.
This is somewhat obvious as the -  characters from the nugget are all grouped at the end of the ciphertext.

The length is also obvious by simply looking at the end of the ciphertext, l = 5.

We use an online scytale solver (link) to get the flag.

Flag:  HV15-OWoV-lO6j-Aqq8-fV7M-Oduv

 
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Posted in Hackvent 2015

 

Advent Of Code: Day 4

04 Dec 2015
CTF: Advent Of Code
Link to challenge: http://adventofcode.com
Date Completed: 04 December 2015

The Challenge

Solution

Because speed was not an issue in this case, I simply used python again to solve the problem. The script is a little slow taking ~10 seconds to compute the answer in my case. A C/C++ solution would be orders of magnitude faster.

 

 
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Posted in Advent Of Code