Hi there, I just pwned the Lost Modulus crypto challenge. I am not sure in how much detail I can talk about it here, **spoiler alert** I just called the given decrypt function on the given flag (converted back to bytes from hex) and ran the script… and to my surprise I got the decoded flag. I didn’t have to learn anything about RSA or how to break it. Because of this I didn’t get the satisfaction because I feel this is now how it was supposed to be solved? Any ideas? (oh and sometimes when I run the script I get an error and sometimes it gives me the correct flag :'))
I gone the same short way to the flag. It was a Python coding exercise. More difficult for me was to understand why this way works. I have taken the flag text and searched the web. You learn why the script works sometimes and sometimes not.
> @Jycerian said: > Hi there, I just pwned the Lost Modulus crypto challenge. I am not sure in how much detail I can talk about it here, **spoiler alert** I just called the given decrypt function on the given flag (converted back to bytes from hex) and ran the script… and to my surprise I got the decoded flag. I didn’t have to learn anything about RSA or how to break it. Because of this I didn’t get the satisfaction because I feel this is now how it was supposed to be solved? Any ideas? heh, I never even thought to solve it by just running it, I understand why it works, and honestly I think it’s kind of a flawed challenge in that regard, because I think a lot of people might do what you did and just be really confused, or not understand what happened but just move on because they got the flag. If you want to learn what is going on, solve it without running the decrypt function. With some basic understanding of how RSA and modular arithmetic works, and what parameters where used to encrypt to the flag, you should be able to do. If you have any questions feel free to PM me >(oh and sometimes when I run the script I get an error and sometimes it gives me the correct flag :')) this is kind of a different issue, but investigating what is happening when it doesn’t decrypt (hint, print out the values for the variables) will also give you a better understanding of what’s happening in RSA
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