Clavdivs (100)
- Challenge description: AVE CLAVDIVS!
- Points: 100
- Contents: message.txt
AVE CLAVDIVS!
MOIv/q.Z>\`n/mZH+m,opm,ZO.ZN/gpo\iox%
The first thing I did when seeing this challenge was google "CLAVDIS cipher" on google. Googling the name of the
challenge, or any hints given in, it will usually help you on the right path. In this case, the first google result was
"Caesar cipher". As most people know, the Caesar cipher works by adding an offset to each alphabetic character of the
input, wrapping around if needed. Essentially, with an offset of 2, A would become C, M would become O, Z
would become B, etc.
However, the input contained symbols as well. My first instinct was that perhaps instead of doing a normal Caesar
cipher, I had to disregard the wrapping part and add an offset to the ascii value of each character instead. I threw
the input into CyberChef
and used the ADD operation to add a constant offset to each character in the encrypted part of the input. And sure
enough, at offset 5 it produced the text RTN{4v3_Caes4r_M0r1tur1_T3_S4lutant}*. Cut off the trailing * character
and we have our first flag.
NOTE: a previous version of the challenge required using SUB 5 instead. This was later changed because it produced invalid ASCII, which would trip some text editors up.