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I am working on a challenge that includes decrypting a piece of ciphertext. The sample decryption provided is as follows: KDEwMTAwMDExMTAxMDEwMTAwMTEwMDExMTAxMDAxMDAwMDExMTEwMDAwMTEwMTAwMTAxMTAxMTAwMTAxMDEwMCwxMDAxKQ —> HaCkTrIcK

My first attempt was to try decoding it as base64 and I could get the following: (101000111010101001100111010010000111100001101001011011001010100,1001)

It seems to be a couple of encrypted binary text along with a key (most probably) but I couldn't find a way to decode it.

So, my question is - is there any way for me to figure out just how the binary data is encoded and how to decode it?

Karim Elezabawy
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  • This isn't really the kind of question that fits here. – schroeder Mar 13 '23 at 18:02
  • Hint: Convert the part after the comma (1001) to decimal, and you get 9. Let's call this K (for key). Now, take the first 7 bits (1010001), and convert this to decimal, and you get 81. Now, subtract K, and you get 72. 72 is ascii for H. Now take the next 7 bits (1101010), convert these to decimal, you get 106. Again, subtract K, and you get 97. 97 is ascii for a. See the pattern? – mti2935 Mar 13 '23 at 18:44
  • @mti2935 that's some amazing sleuthing there! – schroeder Mar 13 '23 at 20:59
  • Thanks @schroeder. I must have too much time on my hands... – mti2935 Mar 13 '23 at 21:23

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