Official TwoForOne Discussion

Official discussion thread for TwoForOne. Please do not post any spoilers or big hints.

Do I need a supercalculator to do this ? I implemented basic solutions related to that type of attack but they seem to only work for low exponents and my computer might have lost two years of life expectancy. What’s the mathematical trick I’m missing ?

Edit : Solved. I’m not sure how but… solved. Also, you probably shouldn’t try to implement your own mathematical functions, they’re probably a lot worse than what the 1337 M4th can do :wink:

Edit2 : Oh, yeah, naming your variables msg1 and msg2 and then using 1 when you need 2, good job ! So, I can say it now : SOLVED and UNDERSTOOD !

This challenge can be solved using different calculators and scripts…

but Is there anybody tried to solve this challenge with CrypTool 2?
It would be great if it is possible to repeat solution using CrypTool!

Guys im kinda new to HTB.
is there any data inside the zip file…cuz i dont see any

Type your comment> @BurnDem said:

Guys im kinda new to HTB.
is there any data inside the zip file…cuz i dont see any

Yes. And a password, indicated on the page of the challenge.
If you entered the password and nothing comes out of the archive, you should try to download it again.

For people asking, this challenge doesn’t require any super calculator or anything of the sort just basic math. I do recommend though that you not use functions you created yourself

Haha, yeah I tried to implement my own functions and it didn’t work – but now that I have a working example I can fix them!

I dont wanna give too much away but did you know SymPy has a really cool function called mod_inverse? It works well for really large numbers in case you aren’t a number theory guru.

I liked this challenge, made me feel stupid but like, in a good way?

Solved this challenge in like 2 minutes. What do these keys have in common?

I notice what the keys have in common, I just have no idea where to go from there. Any sort of nudge would be appreciated.

Spoiler Removed

Spoiler Removed

Try and think of what the public and private keys are actually doing. There is a mathematical theorem that does the same thing

Nice Challenge, need more reading to figure out the attack. anyway solved with full understanding.


compare both keys there is something common between them. :wink:

I think I understand what needs to be done but I feel stupid cause I can’t find a way to get the message1 and 2 into an integer to perform the mathematical functions required. You guys have any hint on how to do that?

@splintercelian I would recommend you check pycrtodome documentation. They might have something ^^

I think I know the theory behind the attack but actually implementing it is causing me problems. Assuming I have “u” (some value that I will use as “e” or “d” in RSA), how do I compute m**u?

Hi there, I’m having some problems to solve this challenge. I’ve tried working with the phi(n) function (from sympy) to calculate the private exponent (d). However until this moment it haven’t worked because it seems a complicate calculation for large numbers (or I don’t know if I’m using the incorrect function since @Fukurou mentioned that It only need basic math). I would thank if someone could advice me or told me If I’ve forgotten a step to find the solution.

@rdanilu your idea is technically correct. However, this amounts to factoring n which at the point is impossible unless you want to wait a while. You need to think more basic number theory. Google can be a great help too

Hi, can I pm someone for a hint on how to start this challenge ?