 This is a video write-up for the channel and Steg it up for 100 points in the steganography category from hack on CTF 2018. The challenge prompt here is it isn't as easy as it looks, and we're given this file to download, which we can go ahead and W get right over here. Cool. So now that we've got it downloaded, we can open it up in our terminal with I've known EOG, and it looks like what would be dark code, don't have in blah, blah, blah, the flag kind of pieces of it redacted. So whatever, we can just kind of deal with that. We know that we're working with a steganography challenge, because this is that category, and that's the name of the challenge. So I wanted to reach forward the classic low hanging fruit, just run it through steg solve. I've used steg solve before in a ton of videos and challenges and problems, et cetera. So if you haven't seen it before, you can google it, download it. It is a Java archive file, go ahead and download and blah, blah, blah. So I'm going to go ahead and just locate where it is on my hard drive, because I know I've used it before. There are probably just tons of copies of it lying around. So once we've got it, we can go ahead and Java jar that program and then hit O to open up a file. If you've got it in the current directory of the challenge, you'll just get everything in there. So now I can see the start of the file here. It's kind of too big for my screen, whatever, I'll deal with it. So you can arrow through different kinds of versions that you're seeing of the image. In this case, it's checking out all the alpha planes and at the least significant bit for the alpha plane, we see a bunch of QR codes. So cool. Let's go ahead and scrape these out, because this must be doing something interesting. So I hit shift and like print screen. So in Linux, I can just get a cursor to go ahead and drag stuff that I'd like to see. And I can save this as put it in the current directory and like 1.png, great. And I know that now I've got to keep track of that other QR code that I wasn't able to fit on the screen. So I kind of moved my finger along my monitor as I scrolled that way. So I'd be able to keep track of it. And now we can go ahead and steal those as well. Save this as I guess 2.png or whatever we want. And then we should have those files that we can want to work with. So if you don't have the Z bar image installed, you can pseudo apt install. I think it's Z bar tools, or even just try and run Z bar image and see if it'll get anything for you. And then that is a command line utility that will allow you to try and decode QR codes just as an image from the command line. So what we can do is I can run Z bar image on 1.png, and it's able to look through all of those QR codes. We can see the start of the flag format just down below. So we've got to go ahead and reverse this. First, let's cut it up. Let's get the second field. So we ignore the cold one in that part of the QR code right there. Let's go ahead and reverse this with tac. So all the lines are flipped. Now we have dart code. So many of these things, blah, blah, blah. And let's remove all of the new line characters. So now we've got the first part of the flag. So we can go ahead and say, this is flag dot text. Let's do the same thing with number two, and then append that to flag dot text. So now we just should have, all right, dark. So many of them will have to make this flag song for so reason. I love my code. So that is the final flag that we need. And that is how we solve this. If you wanted to, you could make a get flag script that would just have to have the one dot PNG and a two dot PNG is just the images that QR code scraped out of that image to begin with. And you can have it just do that exact same thing that we just did in the command line, just cut them up, evaluate them, reverse them, blah, blah, blah. But that is it. That is how we solve that challenge, stick it up, go ahead and mark that as complete. And if you wanted to, you could submit it for 100 points. But unfortunately, the game is over. If you didn't want to join us, another cool people playing the capture the flag games, I know Nighthawk is coming up this weekend and I CTF following that, please do join our discord server link in the description. Cool, cool people to play the games with and team up quick special shout out to the people that support me on Patreon. Thank you guys so much. $1 more a month on Patreon will give you a special shout out just like this at the end of every video so you know you are supporting the channel. $5 and more on Patreon will give you early access to everything that I release on YouTube before it goes live because I normally record in bulk and then gradually upload on like a scheduled release. If you did like this video, please do like comment and subscribe. Link in the description to join our discord server. It is an awesome community of CTF players, programmers and hackers come hang out with me and a bunch of other cool people. I would love to see you guys on Patreon, but I can't wait to see you in the next video. Thanks, see ya.