Tweak how prime-field normalizes to the even square root

Cargo.lock

@@ -2552,7 +2552,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8d162beedaa69905488a8da94f5ac3edb4dd4788b732fadb7bd120b2625c1976"
 dependencies = [
  "data-encoding",
- "syn 1.0.109",
+ "syn 2.0.106",
 ]
 
 [[package]]
@@ -4050,9 +4050,9 @@ dependencies = [
 
 [[package]]
 name = "hex-literal"
-version = "0.4.1"
+version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6fe2267d4ed49bc07b63801559be28c718ea06c4738b7a03c94df7386d2cde46"
+checksum = "bcaaec4551594c969335c98c903c1397853d4198408ea609190f420500f6be71"
 
 [[package]]
 name = "hex_fmt"
@@ -6690,7 +6690,7 @@ version = "0.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "77e878c846a8abae00dd069496dbe8751b16ac1c3d6bd2a7283a938e8228f90d"
 dependencies = [
- "proc-macro-crate 1.3.1",
+ "proc-macro-crate 3.2.0",
  "proc-macro2",
  "quote",
  "syn 2.0.106",

crypto/embedwards25519/Cargo.toml

@@ -14,7 +14,7 @@ all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
 
 [dependencies]
-hex-literal = { version = "0.4", default-features = false }
+hex-literal = { version = "1", default-features = false }
 
 std-shims = { version = "0.1", path = "../../common/std-shims", default-features = false, optional = true }
 

crypto/prime-field/src/lib.rs

@@ -419,7 +419,7 @@ macro_rules! odd_prime_field_with_specific_repr {
             const ONE_MOD_EIGHT: bool = (MODULUS.as_words()[0] % 8) == 1;
             const FIVE_MOD_EIGHT: bool = (MODULUS.as_words()[0] % 8) == 5;
 
-            let sqrt = if THREE_MOD_FOUR {
+            let mut sqrt = if THREE_MOD_FOUR {
               const SQRT_EXP: UnderlyingUint =
                 MODULUS.shr_vartime(2).wrapping_add(&UnderlyingUint::ONE);
               Self(self.0.pow(&SQRT_EXP))
@@ -449,7 +449,10 @@ macro_rules! odd_prime_field_with_specific_repr {
               Self(upsilon * self.0 * (i - Self::ONE.0))
             };
 
-            let sqrt = <_>::conditional_select(&sqrt, &-sqrt, sqrt.0.retrieve().is_odd());
+            // Normalize to the even choice of square root
+            // `let ()` is used to assert how `conditional_negate` operates in-place
+            let () = sqrt.conditional_negate(sqrt.is_odd());
+
             CtOption::new(sqrt, sqrt.square().ct_eq(self))
           }
           fn sqrt_ratio(num: &Self, div: &Self) -> (Choice, Self) {

crypto/secq256k1/Cargo.toml

@@ -14,7 +14,7 @@ all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
 
 [dependencies]
-hex-literal = { version = "0.4", default-features = false }
+hex-literal = { version = "1", default-features = false }
 
 std-shims = { version = "0.1", path = "../../common/std-shims", default-features = false, optional = true }