picoCTF 2023 – MSB

28 March 2023 – Written by Valentin Huber – in ctf, forensics, grep, steg, and stegonline

Challenge

This image passes LSB statistical analysis, but we can’t help but think there must be something to the visual artifacts present in this image… Download the image here

Solution

Since the challenge is called MSB, I put the image through this awesome online steg solver, chose Extract Files/Data and selected all the most significant bits. I then downloaded the data. It looked like the book The History of Don Quixote, but a quick search for picoCTF got me the flag:

Hearing this, Sancho said to him, "Your worship should bear in mind,
Senor Don Quixote, that if the knight has done what was commanded him
in going to present himself before my lady Dulcinea del Toboso, he will
have done all that he was bound to do, and does not deserve further
punishment unless he commits some new offence."
picoCTF{15_y0ur_que57_qu1x071c_0r_h3r01c_ee3cb4d8}

"Thou hast said well and hit the point," answered Don Quixote; and so I
recall the oath in so far as relates to taking fresh vengeance on him,
but I make and confirm it anew to lead the life I have said until such
time as I take by force from some knight another helmet such as this
and as good; and think not, Sancho, that I am raising smoke with straw
in doing so, for I have one to imitate in the matter, since the very
same thing to a hair happened in the case of Mambrino's helmet, which
cost Sacripante so dear."