ff::helpers

Function sqrt_tonelli_shanks

Source 
pub fn sqrt_tonelli_shanks<F: PrimeField, S: AsRef<[u64]>>(
    f: &F,
    tm1d2: S,
) -> CtOption<F>
Expand description

Constant-time implementation of Tonelli–Shanks’ square-root algorithm for p mod 16 = 1.

tm1d2 should be set to (t - 1) // 2, where t = (modulus - 1) >> F::S.

§Implementing Field::sqrt

This function can be used to implement Field::sqrt for fields that both implement PrimeField and satisfy p mod 16 = 1.