elliptic-curve: bump crypto-bigint to v0.2.1 (#673)

elliptic-curve/Cargo.toml

@@ -15,7 +15,7 @@ categories = ["cryptography", "no-std"]
 keywords   = ["crypto", "ecc", "elliptic", "weierstrass"]
 
 [dependencies]
-crypto-bigint = { version = "0.2", features = ["generic-array"] }
+crypto-bigint = { version = "0.2.1", features = ["generic-array"] }
 generic-array = { version = "0.14", default-features = false }
 rand_core = { version = "0.6", default-features = false }
 subtle = { version = "2.4", default-features = false }
@@ -35,8 +35,8 @@ hex-literal = "0.3"
 
 [features]
 default = ["arithmetic"]
-alloc = []
-arithmetic = ["ff", "group"]
+alloc = [] # todo: activate `group/alloc` when weak feature activation is available
+arithmetic = ["crypto-bigint/zeroize", "ff", "group", "zeroize"]
 bits = ["arithmetic", "ff/bits"]
 dev = ["arithmetic", "hex-literal", "pem", "zeroize"]
 ecdh = ["arithmetic", "zeroize"]

elliptic-curve/src/dev.rs

@@ -20,7 +20,7 @@ use ff::{Field, PrimeField};
 use hex_literal::hex;
 
 #[cfg(feature = "bits")]
-use crate::{bigint, group::ff::PrimeFieldBits, ScalarBits};
+use crate::{group::ff::PrimeFieldBits, ScalarBits};
 
 #[cfg(feature = "jwk")]
 use crate::JwkParameters;
@@ -157,14 +157,29 @@ impl PrimeField for Scalar {
 
 #[cfg(feature = "bits")]
 impl PrimeFieldBits for Scalar {
-    type ReprBits = [bigint::Limb; 32 / bigint::LIMB_BYTES];
+    #[cfg(target_pointer_width = "32")]
+    type ReprBits = [u32; 8];
+    #[cfg(target_pointer_width = "64")]
+    type ReprBits = [u64; 4];
 
     fn to_le_bits(&self) -> ScalarBits<MockCurve> {
-        (*self.0.limbs()).into()
+        let mut limbs = Self::ReprBits::default();
+
+        for (i, limb) in self.0.limbs().iter().cloned().enumerate() {
+            limbs[i] = limb.into();
+        }
+
+        limbs.into()
     }
 
     fn char_le_bits() -> ScalarBits<MockCurve> {
-        (*MockCurve::ORDER.limbs()).into()
+        let mut limbs = Self::ReprBits::default();
+
+        for (i, limb) in MockCurve::ORDER.limbs().iter().cloned().enumerate() {
+            limbs[i] = limb.into();
+        }
+
+        limbs.into()
     }
 }
 
@@ -304,7 +319,7 @@ impl From<&Scalar> for FieldBytes {
 
 impl Zeroize for Scalar {
     fn zeroize(&mut self) {
-        self.0.as_mut().zeroize()
+        self.0.as_mut().zeroize();
     }
 }