b00t2root CTF: cuz rsa is lub [RSA Cryptography]

Key Takeaways

[Music] what is going on everybody my name is John Hammond welcome back from the YouTube video we're looking at two roots ETF moving to the cryptography category this is the challenge because RSA is love and it just gives us this prompt for RSA text so I would copy link and download it if I had W get accessible to me except it's a stupid Google Doc so we're just gonna work with that we can go ahead and actually create a API for this I'm gonna crank this up in sublime text you can see a little bit better use your bin environment Python etc etc well paste these in because we have the variables that we need here so I have done many videos on RSA you can track on another one especially when we cover it in Pico is a little bit more there that actually discusses how it's happening how it happens behind the scenes you look at the Wikipedia article you look at the math etc but in this case we know what we're gonna do in the and I'm just gonna run through the process of doing it because that's what our say packed lis is it's one that once you know it it's like okay there are a couple of variations there are a couple tricks but the classic RSA is quick and easy to run through so we have N and if we can check out factor DB if we have that accessible trying to actually f11 there and move out of this page but it's taken some time hang on so in fact DB will paste in that N and we've got P and Q there if that didn't have it which I think originally when we tried this challenge the P and Q weren't present you can run the RSA CTF tool on it and that's available on github and around so I don't know why that's not giving me the full value that's kind of annoying 3 ^ 178 x 22 let's put that in there and see if it see if it goes and this one also that will give me the value that's very weird whatever q okay so now I've got P and Q and we can determine fee right or the totient so because P and Q are both primes the property allows us to find fee as just P minus 1 times Q minus 1 and that's simple and easy so now we can go ahead and do the modular inverse to determine D so I'm gonna do this with from crypto a util dot number import inverse and I believe it's D equals inverse e Phi I'm pretty sure I might have that the other way around but do we have D does that work for us we do have D all right so we can now go ahead and try and calculate M because now that we have the private key D we should be able to raise C to the power of D all mod N and that should be M so we can go ahead and say as a number now let's go ahead and make that hex so let's hex hex that okay and that looks like regular readable characters hopefully to negative 1 so that's all cut off and then we can go ahead and decode that so let's decode hex and know if it print needs to work maybe I had print you know let's just remove our parentheses because that's annoying and I forgot to put hex in that in strings there we go boot to root RSA can be vulnerable so that should be the flag and that's very very simple just know the procedure classical or essay and you can crank out the flag no I had to do that off the top your head is pretty good I don't think there are too many steps in RSA and often times once you've got it down pat you can just kind of hit the I believe button there so boot to root RSA can be vulnerable that is the flag let's go ahead and submit it and 50 points on the table great thank you guys so much for watching if you like this video please do like comment and subscribe join the discord server there is a link in the description it is a really cool place because it has a ton of smart people way smarter than me and we're all willing to tackle a capital flag challenge we're all about learning it's all about cybersecurity it's cool it's cool in classic shout-out to r4j he tackled us before I did it's just Ridge '''l RSA challenge but I know he just jumps in and I'm grateful for those that are willing that can attack these with me you're all part of the community you're all part of the family see you later everybody [Music] [Music] [Music] [Music] [Music] [Music] [Music] [Music] you