Migrate remaining `FieldExt` constants and methods into `ff`

Cargo.toml

@@ -74,4 +74,4 @@ uninline-portable = []
 serde = ["hex", "serde_crate"]
 
 [patch.crates-io]
-ff = { git = "https://github.com/zkcrypto/ff.git", rev = "c070ffbaea8cb17e57f817a91ed0e364ff679b7c" }
+ff = { git = "https://github.com/zkcrypto/ff.git", rev = "054a4d2daf9a9540d4c436fa51f0222e997ad15c" }

src/arithmetic/fields.rs

@@ -30,29 +30,7 @@ pub(crate) trait SqrtTableHelpers: ff::PrimeField {
 
 /// This trait is a common interface for dealing with elements of a finite
 /// field.
-pub trait FieldExt: ff::PrimeField + Ord {
-    /// Modulus of the field written as a string for display purposes
-    const MODULUS: &'static str;
-
-    /// Inverse of `PrimeField::ROOT_OF_UNITY`
-    const ROOT_OF_UNITY_INV: Self;
-
-    /// Generator of the $t-order$ multiplicative subgroup
-    const DELTA: Self;
-
-    /// Inverse of $2$ in the field.
-    const TWO_INV: Self;
-
-    /// Element of multiplicative order $3$.
-    const ZETA: Self;
-
-    /// Obtains a field element congruent to the integer `v`.
-    fn from_u128(v: u128) -> Self;
-
-    /// Obtains a field element that is congruent to the provided little endian
-    /// byte representation of an integer.
-    fn from_bytes_wide(bytes: &[u8; 64]) -> Self;
-}
+pub trait FieldExt: ff::WithSmallOrderMulGroup<3> + Ord {}
 
 /// Parameters for a perfect hash function used in square root computation.
 #[cfg(feature = "sqrt-table")]

src/curves.rs

@@ -18,10 +18,13 @@ use group::{
 use rand::RngCore;
 use subtle::{Choice, ConditionallySelectable, ConstantTimeEq, CtOption};
 
+#[cfg(feature = "alloc")]
+use ff::WithSmallOrderMulGroup;
+
 use super::{Fp, Fq};
 
 #[cfg(feature = "alloc")]
-use crate::arithmetic::{Coordinates, CurveAffine, CurveExt, FieldExt};
+use crate::arithmetic::{Coordinates, CurveAffine, CurveExt};
 
 macro_rules! new_curve_impl {
     (($($privacy:tt)*), $name:ident, $name_affine:ident, $iso:ident, $base:ident, $scalar:ident,

src/fields/fp.rs

@@ -1,7 +1,7 @@
 use core::fmt;
 use core::ops::{Add, Mul, Neg, Sub};
 
-use ff::{Field, PrimeField};
+use ff::{Field, FromUniformBytes, PrimeField, WithSmallOrderMulGroup};
 use rand::RngCore;
 use subtle::{Choice, ConditionallySelectable, ConstantTimeEq, CtOption};
 
@@ -563,11 +563,30 @@ impl ff::Field for Fp {
 impl ff::PrimeField for Fp {
     type Repr = [u8; 32];
 
+    const MODULUS: &'static str =
+        "0x40000000000000000000000000000000224698fc094cf91b992d30ed00000001";
+    const TWO_INV: Self = Fp::from_raw([
+        0xcc96987680000001,
+        0x11234c7e04a67c8d,
+        0x0000000000000000,
+        0x2000000000000000,
+    ]);
     const NUM_BITS: u32 = 255;
     const CAPACITY: u32 = 254;
     const MULTIPLICATIVE_GENERATOR: Self = GENERATOR;
     const S: u32 = S;
     const ROOT_OF_UNITY: Self = ROOT_OF_UNITY;
+    const ROOT_OF_UNITY_INV: Self = Fp::from_raw([
+        0xf0b87c7db2ce91f6,
+        0x84a0a1d8859f066f,
+        0xb4ed8e647196dad1,
+        0x2cd5282c53116b5c,
+    ]);
+    const DELTA: Self = DELTA;
+
+    fn from_u128(v: u128) -> Self {
+        Fp::from_raw([v as u64, (v >> 64) as u64, 0, 0])
+    }
 
     fn from_repr(repr: Self::Repr) -> CtOption<Self> {
         let mut tmp = Fp([0, 0, 0, 0]);
@@ -709,36 +728,21 @@ impl SqrtTableHelpers for Fp {
     }
 }
 
-impl FieldExt for Fp {
-    const MODULUS: &'static str =
-        "0x40000000000000000000000000000000224698fc094cf91b992d30ed00000001";
-    const ROOT_OF_UNITY_INV: Self = Fp::from_raw([
-        0xf0b87c7db2ce91f6,
-        0x84a0a1d8859f066f,
-        0xb4ed8e647196dad1,
-        0x2cd5282c53116b5c,
-    ]);
-    const DELTA: Self = DELTA;
-    const TWO_INV: Self = Fp::from_raw([
-        0xcc96987680000001,
-        0x11234c7e04a67c8d,
-        0x0000000000000000,
-        0x2000000000000000,
-    ]);
+impl FieldExt for Fp {}
+
+impl WithSmallOrderMulGroup<3> for Fp {
     const ZETA: Self = Fp::from_raw([
         0x1dad5ebdfdfe4ab9,
         0x1d1f8bd237ad3149,
         0x2caad5dc57aab1b0,
         0x12ccca834acdba71,
     ]);
+}
 
-    fn from_u128(v: u128) -> Self {
-        Fp::from_raw([v as u64, (v >> 64) as u64, 0, 0])
-    }
-
+impl FromUniformBytes<64> for Fp {
     /// Converts a 512-bit little endian integer into
     /// a `Fp` by reducing by the modulus.
-    fn from_bytes_wide(bytes: &[u8; 64]) -> Fp {
+    fn from_uniform_bytes(bytes: &[u8; 64]) -> Fp {
         Fp::from_u512([
             u64::from_le_bytes(bytes[0..8].try_into().unwrap()),
             u64::from_le_bytes(bytes[8..16].try_into().unwrap()),

src/fields/fq.rs

@@ -1,7 +1,7 @@
 use core::fmt;
 use core::ops::{Add, Mul, Neg, Sub};
 
-use ff::{Field, PrimeField};
+use ff::{Field, FromUniformBytes, PrimeField, WithSmallOrderMulGroup};
 use rand::RngCore;
 use subtle::{Choice, ConditionallySelectable, ConstantTimeEq, CtOption};
 
@@ -563,11 +563,30 @@ impl ff::Field for Fq {
 impl ff::PrimeField for Fq {
     type Repr = [u8; 32];
 
+    const MODULUS: &'static str =
+        "0x40000000000000000000000000000000224698fc0994a8dd8c46eb2100000001";
     const NUM_BITS: u32 = 255;
     const CAPACITY: u32 = 254;
+    const TWO_INV: Self = Fq::from_raw([
+        0xc623759080000001,
+        0x11234c7e04ca546e,
+        0x0000000000000000,
+        0x2000000000000000,
+    ]);
     const MULTIPLICATIVE_GENERATOR: Self = GENERATOR;
     const S: u32 = S;
     const ROOT_OF_UNITY: Self = ROOT_OF_UNITY;
+    const ROOT_OF_UNITY_INV: Self = Fq::from_raw([
+        0x57eecda0a84b6836,
+        0x4ad38b9084b8a80c,
+        0xf4c8f353124086c1,
+        0x2235e1a7415bf936,
+    ]);
+    const DELTA: Self = DELTA;
+
+    fn from_u128(v: u128) -> Self {
+        Fq::from_raw([v as u64, (v >> 64) as u64, 0, 0])
+    }
 
     fn from_repr(repr: Self::Repr) -> CtOption<Self> {
         let mut tmp = Fq([0, 0, 0, 0]);
@@ -708,36 +727,21 @@ impl SqrtTableHelpers for Fq {
     }
 }
 
-impl FieldExt for Fq {
-    const MODULUS: &'static str =
-        "0x40000000000000000000000000000000224698fc0994a8dd8c46eb2100000001";
-    const ROOT_OF_UNITY_INV: Self = Fq::from_raw([
-        0x57eecda0a84b6836,
-        0x4ad38b9084b8a80c,
-        0xf4c8f353124086c1,
-        0x2235e1a7415bf936,
-    ]);
-    const DELTA: Self = DELTA;
-    const TWO_INV: Self = Fq::from_raw([
-        0xc623759080000001,
-        0x11234c7e04ca546e,
-        0x0000000000000000,
-        0x2000000000000000,
-    ]);
+impl FieldExt for Fq {}
+
+impl WithSmallOrderMulGroup<3> for Fq {
     const ZETA: Self = Fq::from_raw([
         0x2aa9d2e050aa0e4f,
         0x0fed467d47c033af,
         0x511db4d81cf70f5a,
         0x06819a58283e528e,
     ]);
+}
 
-    fn from_u128(v: u128) -> Self {
-        Fq::from_raw([v as u64, (v >> 64) as u64, 0, 0])
-    }
-
+impl FromUniformBytes<64> for Fq {
     /// Converts a 512-bit little endian integer into
     /// a `Fq` by reducing by the modulus.
-    fn from_bytes_wide(bytes: &[u8; 64]) -> Fq {
+    fn from_uniform_bytes(bytes: &[u8; 64]) -> Fq {
         Fq::from_u512([
             u64::from_le_bytes(bytes[0..8].try_into().unwrap()),
             u64::from_le_bytes(bytes[8..16].try_into().unwrap()),

src/hashtocurve.rs

@@ -1,14 +1,14 @@
 //! This module implements "simplified SWU" hashing to short Weierstrass curves
 //! with a = 0.
 
-use ff::{Field, PrimeField};
+use ff::{Field, FromUniformBytes, PrimeField};
 use static_assertions::const_assert;
 use subtle::ConstantTimeEq;
 
-use crate::arithmetic::{CurveExt, FieldExt};
+use crate::arithmetic::CurveExt;
 
 /// Hashes over a message and writes the output to all of `buf`.
-pub fn hash_to_field<F: FieldExt>(
+pub fn hash_to_field<F: FromUniformBytes<64>>(
     curve_id: &str,
     domain_prefix: &str,
     message: &[u8],
@@ -73,7 +73,7 @@ pub fn hash_to_field<F: FieldExt>(
         let mut little = [0u8; CHUNKLEN];
         little.copy_from_slice(big.as_array());
         little.reverse();
-        *buf = F::from_bytes_wide(&little);
+        *buf = F::from_uniform_bytes(&little);
     }
 }
 

src/lib.rs

@@ -39,8 +39,8 @@ pub extern crate group;
 #[cfg(feature = "alloc")]
 #[test]
 fn test_endo_consistency() {
-    use crate::arithmetic::{CurveExt, FieldExt};
-    use group::Group;
+    use crate::arithmetic::CurveExt;
+    use group::{ff::WithSmallOrderMulGroup, Group};
 
     let a = pallas::Point::generator();
     assert_eq!(a * pallas::Scalar::ZETA, a.endo());