Crypto Challenge
A mysterious file has been recovered, containing an encoded message.
At first glance, it may seem simple — but appearances can be deceiving. Hidden beneath layers of encoding lies the secret you’re looking for.
Your mission is to analyze, decode, and follow the trail until you uncover the flag.
Flag Format: ENIGMA{…}
This is my challenge.
So the first thing I noticed that the file didn’t have a proper extension, it just said file and when I tried to open it prompted me to select an app and not open with a default one.
I honestly don’t know why this came to mind, but I remembered accidentally opening a binary file in Notepad once and seeing a screen full of gibberish.
So out of the option I opted the notepad app and there I got this random string of alphanumerics.
I copied the contents into dCode to identify what kind of encoding I was dealing with and it showed chances of it being base62 and base64.
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We were dealing with base64 in the session where I got this task from so naturally I opened Cyber chef and pasted it there and decoded to get this
The decoded output still ended with an “=” sign, which usually indicates another layer of Base64. However, the surrounding quotes and the mysterious b prefix made me hesitate.
But still just to try I did it again and got bunch of gibberish
So I searched it and then I learned the prefix b indicates that the content inside the quotes are a stream of bytes and not standard Unicode string. So I should indeed remove those and convert again.
But then I get this LUPNTH{jhlzhy_k3jy9wa3k_m0212758}
I was already given the format of the flag so I should be getting a flag starting with ENIGMA
Went to DCode and then learned this cypher was the famous “Caesar Cypher or ROT”
Again, went to Cyber Chef and starting rotating from 1 letter to the next till I got the one by rotating the letter nineteen times.
and there it is.
Although the challenge itself was simple, it introduced me to layered encodings and reinforced an important lesson: never assume the first decoded output is the final answer. Many crypto challenges require peeling away one layer at a time.
