The Time Challenge by V4l

V4l, one of our CTF creators at TWC created this challenge, it uses multiple steganography and cryptography techniques and good for beginners who are trying their hand at CTFs. Lets solve this!

Follow The White Rabbit...

Like always I start with the file command...

$ file thewhiterabbit.png
thewhiterabbit.png: PNG image data, 836 x 456, 8-bit/color RGBA, non-interlaced

After trying various tools such as exiftool, pngcheck, strings I finally landed on zsteg!

$ zsteg thewhiterabbit.png

b1,rgb,lsb,xy       .. text: "You need time : RxabLA7UQ9k \n\nbnnjm://jumnyvch.wig/y49gG4xD \n\n"
b1,bgr,lsb,xy       .. text: "9!AmUEcn"
b1,rgba,lsb,xy      .. text: "q]39QW{[YW"
b2,g,lsb,xy         .. text: "AEAUAQEUAUDDDP@"
b2,rgb,msb,xy       .. text: "\"( (*(*(\"("
b3,r,lsb,xy         .. file: gfxboot compiled html help file
b3,rgb,lsb,xy       .. file: gfxboot compiled html help file
b3,rgb,msb,xy       .. file: Apple DiskCopy 4.2 image H\200 A\222 \011\202, 8388617 bytes, 0x92200882 tag size, 0x90 encoding, 0x0 format
b4,r,lsb,xy         .. file: PDP-11 UNIX/RT ldp
b4,rgb,lsb,xy       .. file: Targa image data (257-4368) 4096 x 65536 x 1 +4353 +257 - right "\021\020\001\020\001\001\001\020\001\001\001\020\001"

# Take a look at the text part
#
#==============================
# You need time : RxabLA7UQ9k 

# bnnjm://jumnyvch.wig/y49gG4xD
#==============================

Second string looks like Caesar cipher, lets try to decode it using dcode.fr...

So it is a Caesar cipher with a shift of 20 and look it's a pastebin URL...

Title   -> youneedtorotbysomethingbutwhichone?
content -> gssor://vvv.xntstad.bnl/vzsbg?u=

Title tells us what to do and if you observe the content it looks like a URL and we need to shift each alphabet by 1 to get the URL

https://www.youtube.com/watch?v=

Interesting but we need a video ID as well, lets head back a little...

You need time : RxabLA7UQ9k

lets try this as the video id

https://www.youtube.com/watch?v=RxabLA7UQ9k

It is a valid link to a video, lets take a look at the comments section...

V4l has added a comment here, lets drop this string in CyberChef and use From Hex...

An anonfiles URL which is serving a WAV file, for this stage we got a hint from V4l : "look DEEP into the SOUND", DeepSound is a popular steganography tool used for hiding/revealing data inside audio files, it was also featured in Mr. Robot!

Usage is very simple but unfortunately we need windows for this step :(

Inside there is a congrats.txt file and we have solved it! Thank you v4l for creating this challenge, suitable for beginners, looking forward to more such challenges!