Bill Allombert on Tue, 05 Nov 2019 16:36:34 +0100

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Re: Finding Y coordinate

On Tue, Nov 05, 2019 at 03:15:02PM +0000, Tiago Mendes wrote:
> Good afternoon,
> I am writing a file in C using the PARI C Library  and need some help. This is what i want to do:
> - Given 
> 		—— a prime p,  and
> 		—— the coordinate X  
> i want to obtain the value of Y coordinate from the curve Y^2 = X^3 +
> 7 (mod p) , knowing for example that Y is positive. 

You can use Fp_sqrt.
Did you already write a C file ? Could you share it ?
It would be easier to help you.