EC implementation on Edward curves : what modulo is used in implementation?

cn flag

I'm trying to implement EC scalar multiplication in the fastest way possible (but still with a good curve) on a GPU.
I'm specifically looking to implement it based on and trying to use other curves like Curve25519 (or Edwards25519, I believe it's a representation difference).
I noticed all calculations on x and y coordinates are done modulo some number n (I believe it's the number that the code is meant to brute-force factor).
If I'm not looking to brute-force factor a number but simply to implement EC scalar multiplication using this code, what number should I use for modulus calculations ?

(NB: I'm still a beginner in EC cryptography, so links to the appropriate resources are welcome)

Bonus question: should I use extended or inverted coordinates ?

kelalaka avatar
in flag
$n$ is the prime number that curve is defined. It is $2^{255}-19$ where the name comes. [EdDSA](
fgrieu avatar
ng flag
And that prime number $2^{255}-19$ is generally noted $p$, not $n$.
kelalaka avatar
in flag
And [RFC 8032]( is your guide.
knaccc avatar
es flag
See which is a Curve25519 GPU implementation

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