misc/Echoes of Arrakis

58 solves / 447 points

Writeup by Aryan

The challenge originally provides you with two files: a video titled fremen_filmbook.webm and some weird file titled fremen_filmbook.srt. Watching the video provides nothing of value, so I took a closer look at the .srt file format. Turns out this is a SubRip file, which contains info about a video's subtitles. The data is stored in plaintext, making it easy to read.

Opening the file in Notepad and scrolling through, we notice two interesting subtitles.

With these two lines, we are able to deduce the data is encrypted with Vigenere Cipher. Decoding it with our key being "Fremen" gives the following text: THE ANSWER LIES WITHIN THE STORY OF THE SANDWORMS: https://youtu.be/3cS-Q-JglHU.

The video is Morse Code. At this point I only had 15 minutes left in the CTF so I tried to find some online audio decoder. Some of the first results incorrectly decoded the audio, but this did the trick.

Flag: UMDCTF{0n3_573p_cl053r_70_d353r7_p0w3r}