47 lines
1.2 KiB
Markdown
47 lines
1.2 KiB
Markdown
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## 5x5 Crypto
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The main idea finding the flag is by simple pairs.
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#### Step-1:
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After reading the given text:
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`Ever heard of the 5x5 secret message system? If not, basically it's a 5x5 grid with all letters of the alphabet in order, without k because c is represented to make the k sound only. Google it if you need to. A letter is identified by Row-Column. All values are in caps. Try: 1-3,4-4,2-1,{,4-4,2-3,4-5,3-2,1-2,4-3,_,4-5,3-5,}`
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#### Step-2:
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So, basically the table is:
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<img src="Table.png">
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We can decode the message according to given inputs in message above to get the flag.
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#### Step-3:
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Instead I wrote a `Flag.py` script to get the flag.
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```
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import numpy as np
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arr = np.arange(65,90).reshape(5, 5) # Array of alphabet
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arr = np.where(arr <75, arr, arr+1) # Array without 'K'
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cells = ["1-3","4-4","2-1","{","4-4","2-3","4-5","3-2","1-2","4-3","_","4-5","3-5","}"]
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for i in cells:
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if(ord(i[0])>=48 and ord(i[0])<=57):
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x=int(i[0])-1
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y=int(i[2])-1
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print(chr(arr[x][y]),end="")
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else:
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print(i[0],end="")
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print("\n")
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```
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#### Step-4:
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If we execute this script by `python3 Flag.py`, I got the following output:
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```
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CTF{THUMBS_UP}
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```
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#### Step-5:
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Finally the flag becomes:
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`CTF{THUMBS_UP}`
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