[WIP] Impl ff::Field for Scalar
#471
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For the field element types `FieldElement` and `Scalar`, use inherent constants instead of (non-const) functions to return these constant values. It's likely the original functions predate support for inherent constants, but now that they're available, they're a better fit for these sort of constant values.
Adds https://github.com/zkcrypto/ff as an optional dependency, which provides traits for finite fields.
| @@ -568,6 +571,36 @@ impl Zeroize for Scalar { | |||
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| #[cfg(all(feature = "ff", feature = "rand_core"))] | |||
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Would be nice to use namespaced features so an ff feature could activate dep:ff and rand_core
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We will be using this in ff itself once its MSRV is 1.60 (zkcrypto/ff#78), but I haven't seen a strong push for that MSRV yet in the wider ecosystem.
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| fn sqrt_ratio(_num: &Self, _div: &Self) -> (Choice, Self) { | ||
| // TODO: can't use `ff::helpers::sqrt_ratio_generic` because `Scalar` isn't a `PrimeField` |
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The documentation of Scalar indicates that its arithmetic is modulo ell, the prime order of both Ristretto and the Ed25519 basepoint. So we can impl PrimeField for Scalar. (It does have concrete constructors for bit-twiddling purposes that enable construction of scalar representations that aren't canonical, but those are irrelevant to the ff::PrimeField trait, and any arithmetic on those representations would result in canonical scalars.)
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Closing in favor of #473 |
Note: depends on #470 which needs to be merged first.
Adds https://github.com/zkcrypto/ff as an optional dependency, which provides traits for finite fields.