CodeGate CTF 2011 : Crypto – 100 Points

File given to us:
This is the original file:

Recommended Tools:
Brains

Solving the Puzzle:
First, i took a look at the image and all i can see is numbers. o.O”

After looking at the image for an hour or so, then i realised something is strange as it didn’t contain “0” and “1”.

I just couldn’t figure it out until my phone rang and i saw the “abc” on the keys.

Hmmm…could it be using that to change the numbers to actual letters?

So i took out my old handphone and type in numbers via a SMS and i got back this text.

In cryptography, a substitution cipher is a method of encryption by which units of plain text are replaced with cipher text according to a regular system.
The units may be single letters, pairs of letters, triplets of letters, mixtures of the above.
This cipher text is encrypted by telephone key pad, so we call this keypad cipher.

Correct Key:
So i type in keypad cipher and we added another 100points.

cheers
0x4a61636f62

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