This problem is called RSABC.

I’d assume this problem has something to do with RSA. Just a guess. And It could maybe have something to do with the “ABC’s” of RSA. Who knows.

Lets click the links.

 The first link we get is a link to a very refreshing ASMR video of a medieval battle.  

 After a few minutes of relaxing, I opened the second link.

Here we find a familiar set of numbers, an N, an E, and a C.  

 So since we have everything, this shouldn’t be that hard to decipher.

After a few minutes of online searching, I cam across a stack overflow post where one guy suggested using a tool called RsaCtfTool

 Here is the link to it:

After I cloned it to my desktop on kali linux, I opened up a terminal. I cd into the directory of the tool.

 lets go back to the post to see how to format our command.

which explains to do it as python RSACtfTool – n {n} -e {e} –uncipher {c}

I replicate the command using the numbers we got from the challenge. Then I press enter.

Hmm, we got an error.

I figured I would try the command using python3 instead of python.

 It worked! The tool ‘unciphered’ the cipher. (Down there at the bottom)

Flag: tjctf{BOLm1QMWi3c}

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