 What's up guys this is a video write-up for the challenge ether hide for 40 points in the miscellaneous category of hack on 2018 capture the flag So this challenge from here is my friend heard about the theory in blockchain and thinks it's the safest place to hide stuff prove Him wrong and it gives us a network to would do whatever with and a contract address I didn't actually end up using this at all. I didn't even realize it was there to be completely honest I am not an authority to really be going over this challenge I just kind of poked around and found it eventually. So what I had done not knowing a whole lot about Like cryptography like cryptocurrencies, etc. Etc. I was assuming okay at through a theorem is kind of like Bitcoin And that is a cryptocurrency. I know there's a Bitcoin wallet So is there such thing as an Ethereum wallet? I googled that and I found my ether wallet or my ether wallet calm And it looked like I was able to change up at the very top right the network that I was on Originally, I was just on eth my ether wallet calm But I was able to move it down and I saw that if I choose Robston which is that network that it specifies Robston test network I couldn't tell the difference between Robston my ether wallet and Robston infura So I was assuming the second one was their test network. So I just switched over to that And then I went to view wallet info because it didn't look like I wanted to create a wallet I just wanted to find some other wallet and it asks, okay How would you like to access a wallet and I look through this list? It looked like I could supply an address and that's what I had I had an address so I copied and pasted what I had in there can view that balance and it gives me Whatever this is it looks like it okay a QR code. I could have decoded that but it would just give me what we've already seen So it's okay, I can look at the transaction history over at this URL So I went ahead and tried to take a look at that at this point I'm looking at things that I don't understand and don't know what they are but it looked like okay, these are transactions these are things happening during the time of the competition and It gave me a value as to whether or not there was ether going through or like actual money working with it And I saw this one that was one decimal three three seven ether and that looked like elite So I thought okay that has to be a lead for a flag or something So I went ahead and clicked on that thing I scrolled down and it looked like okay Check data string data and there's some stuff here after I look through it in okay I got the note that this value looks like hex so what I did was I went ahead and Checked out what that hex might be by Python right? I did that dot decode hex And there was the flag with the null byte character at the very end So okay, let's go ahead and take that and use that as our get flag script because we've solved the challenge just now We we did it already so simple miscellaneous category But we can remove those null bytes there That is a little bit of the reconnaissance that I had done or at least what I kind of poked around with trying to bang my head Against the wall until I knew what I was really working with there. I totally put the wrong shebang line so simple challenge, but Finding your way and poking around and if you wanted to learn more about blockchain But I or crypto currencies, but I didn't particularly want to at the time It was still easy enough to find the flag just like that so we can mark that challenge as complete You could submit it for points. However, unfortunately, the game is no longer live If you would like to play other caps to fly competitions, please join our discord server link in the description Super quick shout out to the people that support me on patreon. Thank you guys so much You're the best one dollar or more on patreon a month will give you a special shout out Just like this at the end of every video five dollars or more on patreon I'll give you early access to everything they release on YouTube before it goes live because I normally record in bulk And then gradually release them if you did like this video, please do that like comment and subscribe Join the discord server link in the description. It's a cool community of CTO players programmers and hackers And I'd love to see you guys in the next video. Bye