Tags: defcon ctf 

Rating: 0

Well this was one of the more interesting flags this year at the DefCon CTF Qualifiers. It was a throw back to pretty cool old school decryption.

Here is what I did to solve it:

1. They give you a single text file and no URL to poke at.
2. The content of the text file was as follows:

> Anyo!e!howouldsacrificepo!icyforexecu!!onspeedthink!securityisacomm!ditytop!urintoasy!tem!

Looking at this it is hard at first to make much of a connection out of the data.

3. First I considered the possibility that it required you to shift letters or choose letters in a patterned fashion like every other letter.
4. Looking at all of this I wasnt able to make much sense or see a pattern that fit.
5. However it dawned on me that if we counted the letters between the ! marks that maybe I could try it as traditional alaphbet cipher.
6. The values that you get when you try this method is as follows:

4
1
18
11
0
12
15
7
9
3

7. At first I tried what is a more traditional alphabet cipher which is as follows:

A=0
B=1
C=3

and so on.

8. However when I tried this I found that it resulted in an answer that made no sense.
9. I thought back to the clue and they mentioned that the flag was in a non-standard form and multiple word seperated with a space.
10. Seeing that it had atleast one space in it I noticed the 0 was in the middle of the number string and tried shifting the letters over to allow 0 to equal a space.
11. When I did that I got the following:

D
A
R
K

L
O
G
I
C

12. And with that I found the flag:

dark logic