Crypto 6 - Writeup

Crypto 6 - Valentine CTF 2020


The challenge gives you a file, when you open it you see this weird text.

D’AM]>\6;4zVDTBu@?sqp(^Km7ZiFD%e#dbQ,vN)sxZpunm3kjih.ONdcha'eGc\[!YXW\[TSwQVUNrR43ImMLKD,HAeE>=B;:9]=6|:981Uv.32+*)M-,+*)iF~}${zy?}_{t:xZvo5slkji/mfN+iKg%]\aZYX|[Z<RvVUNSRQJnHMLEDhB*FE>bB$@?>=<5Y9876v43,+O/o-&+#G'&%|{A!~}|^]s9qYo5mrqpongf,diba`edc\"ZY}@\UZYRvP8TMq43ImMLK-IBfF?'=a@9]~}5:32V0/St210/(L,%)"!Ef#"!~}v<t\xq7XWsl2Song-NMiba&d]ba^WVz=<XWPOsSRQP2HGFjDIHG@dD=%;_?!7<5:981U54-2+O/o-&J$)"F&%|dz@~}|^]s9Zvo5Vrqjing-kdiba’r


Approach
As we have said before, you need to be familiar with the most popular ciphers/ encoding methods. This text seems like ‘Malbolge’, which is an esoteric programming language used for encoding.
Let’s try out a Malbolge interpreter and see what will the program output.

As we can see, the program outputs the flag.