Smash Ciphersuite definitions into their own crates

Uses dalek-ff-group for Ed25519 and Ristretto. Uses minimal-ed448 for Ed448.
Adds ciphersuite-kp256 for Secp256k1 and P-256.

crypto/dalek-ff-group/Cargo.toml

@@ -25,18 +25,22 @@ subtle = { version = "^2.4", default-features = false }
 rand_core = { version = "0.6", default-features = false }
 
 digest = { version = "0.10", default-features = false }
+sha2 = { version = "0.10", default-features = false }
 
 ff = { version = "0.13", default-features = false, features = ["bits"] }
 group = { version = "0.13", default-features = false }
+ciphersuite = { path = "../ciphersuite", default-features = false }
 
 crypto-bigint = { version = "0.5", default-features = false, features = ["zeroize"] }
 
 curve25519-dalek = { version = ">= 4.0, < 4.2", default-features = false, features = ["alloc", "zeroize", "digest", "group", "precomputed-tables"] }
 
 [dev-dependencies]
+hex = "0.4"
 rand_core = { version = "0.6", default-features = false, features = ["std"] }
 ff-group-tests = { path = "../ff-group-tests" }
 
 [features]
-std = ["zeroize/std", "subtle/std", "rand_core/std", "digest/std"]
+alloc = ["zeroize/alloc", "ciphersuite/alloc"]
+std = ["alloc", "zeroize/std", "subtle/std", "rand_core/std", "digest/std", "sha2/std", "ciphersuite/std"]
 default = ["std"]

crypto/dalek-ff-group/src/ciphersuite.rs

@@ -0,0 +1,94 @@
+use zeroize::Zeroize;
+
+use sha2::{Digest, Sha512};
+
+use group::Group;
+use crate::Scalar;
+
+use ciphersuite::Ciphersuite;
+
+macro_rules! dalek_curve {
+  (
+    $feature: literal,
+
+    $Ciphersuite: ident,
+    $Point:       ident,
+    $ID:          literal
+  ) => {
+    use crate::$Point;
+
+    impl Ciphersuite for $Ciphersuite {
+      type F = Scalar;
+      type G = $Point;
+      type H = Sha512;
+
+      const ID: &'static [u8] = $ID;
+
+      fn generator() -> Self::G {
+        $Point::generator()
+      }
+
+      fn hash_to_F(dst: &[u8], data: &[u8]) -> Self::F {
+        Scalar::from_hash(Sha512::new_with_prefix(&[dst, data].concat()))
+      }
+    }
+  };
+}
+
+/// Ciphersuite for Ristretto.
+///
+/// hash_to_F is implemented with a naive concatenation of the dst and data, allowing transposition
+/// between the two. This means `dst: b"abc", data: b"def"`, will produce the same scalar as
+/// `dst: "abcdef", data: b""`. Please use carefully, not letting dsts be substrings of each other.
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Zeroize)]
+pub struct Ristretto;
+dalek_curve!("ristretto", Ristretto, RistrettoPoint, b"ristretto");
+#[test]
+fn test_ristretto() {
+  ff_group_tests::group::test_prime_group_bits::<_, RistrettoPoint>(&mut rand_core::OsRng);
+
+  assert_eq!(
+    Ristretto::hash_to_F(
+      b"FROST-RISTRETTO255-SHA512-v11nonce",
+      &hex::decode(
+        "\
+81800157bb554f299fe0b6bd658e4c4591d74168b5177bf55e8dceed59dc80c7\
+5c3430d391552f6e60ecdc093ff9f6f4488756aa6cebdbad75a768010b8f830e"
+      )
+      .unwrap()
+    )
+    .to_bytes()
+    .as_ref(),
+    &hex::decode("40f58e8df202b21c94f826e76e4647efdb0ea3ca7ae7e3689bc0cbe2e2f6660c").unwrap()
+  );
+}
+
+/// Ciphersuite for Ed25519, inspired by RFC-8032.
+///
+/// hash_to_F is implemented with a naive concatenation of the dst and data, allowing transposition
+/// between the two. This means `dst: b"abc", data: b"def"`, will produce the same scalar as
+/// `dst: "abcdef", data: b""`. Please use carefully, not letting dsts be substrings of each other.
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Zeroize)]
+pub struct Ed25519;
+dalek_curve!("ed25519", Ed25519, EdwardsPoint, b"edwards25519");
+#[test]
+fn test_ed25519() {
+  ff_group_tests::group::test_prime_group_bits::<_, EdwardsPoint>(&mut rand_core::OsRng);
+
+  // Ideally, a test vector from RFC-8032 (not FROST) would be here
+  // Unfortunately, the IETF draft doesn't provide any vectors for the derived challenges
+  assert_eq!(
+    Ed25519::hash_to_F(
+      b"FROST-ED25519-SHA512-v11nonce",
+      &hex::decode(
+        "\
+9d06a6381c7a4493929761a73692776772b274236fb5cfcc7d1b48ac3a9c249f\
+929dcc590407aae7d388761cddb0c0db6f5627aea8e217f4a033f2ec83d93509"
+      )
+      .unwrap()
+    )
+    .to_bytes()
+    .as_ref(),
+    &hex::decode("70652da3e8d7533a0e4b9e9104f01b48c396b5b553717784ed8d05c6a36b9609").unwrap()
+  );
+}

crypto/dalek-ff-group/src/lib.rs

@@ -38,6 +38,9 @@ use group::{
 mod field;
 pub use field::FieldElement;
 
+mod ciphersuite;
+pub use crate::ciphersuite::{Ed25519, Ristretto};
+
 // Use black_box when possible
 #[rustversion::since(1.66)]
 mod black_box {