Cutomize curve without p value
hasuwasu opened this issue · comments
Hi!
I saw a similar question was asked, but I'm trying to generate a custom Curve() with my own parameters and I can't find how to exclude p value since I'm using y^2 = x^3 + 7 (NIST256P) and I don't need the modulus. I looked through the official documentation but didn't see anything that answered this question. My only thought was to make p a huge value, but I'm sure there's a better way.
What are you trying to do? If you’re working with numbers that are comparable in size to what one normally would use in a cryptographic context your x and y values are going to get REALLY big very quickly given what you propose. Meaning so big you can’t do efficient computations with them.
I want to create my own curve to test against data I'm given for a CTF challenge. I'm given the curve, the generator points x & y, the group order, another point x & y, the public key, & two messages with their sigantures one which does not have the first part of the signature. I want to create a NIST256P curve using the init function to test outputs but I don't want to use p in the function. I'm still learning ecc so I apologize if my explanation isn't very clear.
Edit
I got an explanation from a friend. I understand now what you mean by the REALLY big numbers by excluding the mod. I think my previous question should be directed to another forum.
Edit 2
I apologize, I think I got it. I'm supposed to use the size of the key as the p value so 2^256. I was confused because I saw an example showing this curve as y^2 = x^3 + 7 but the mod 2^256 should be at the end regardless.
Yes, the mod p
is sometimes left out of the equation, many places just assume all operations are done in the field with characteristic p
, which can lead to confusion. Glad you were able to get clarification on your initial issue.