Interencdec-PicoCTF Writeup

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Description :Can you get the real meaning from this file.

Category :Cryptography

Author: NGIRIMANA SCHADRACK

Flag format : picoCTF{FLAG}

First started to inspect the given file and recognized the structure of the content as a Base64-encoded string.Base64 padding often appears at the end as = or ==.

To decode this I executed this command in my terminal

echo YidkM0JxZGtwQlRYdHFhR3g2YUhsZmF6TnFlVGwzWVROclgyMHdNakV5TnpVNGZRPT0nCg== | base64 --decode

And the result was another encoded string

“ b'd3BqdkpBTXtqaGx6aHlfazNqeTl3YTNrX20wMjEyNzU4fQ=='

Here the leading b stands for bytes literal and the content inside the quotes is our actual data.

I decoded it using the same method, which gave me the following text:

“ wpjvJAM{jhlzhy_k3jy9wa3k_m0212758}

It shows that we cannot do decryption further, hence used an online tool dCode .

Once, inputting the decoded string, the tool identified it as a Caesar cipher.

Using the dCode tool’s Caesar cipher decryption utility, I decrypted the message. And there we got the Flaggg!!!

The correct Flag:

picoCTF{caesar_d3cr9pt3d_f0212758}

THANK YOU!!