1 files changed, 58 insertions, 0 deletions
diff --git a/spake2/src/group.rs b/spake2/src/group.rs
new file mode 100644
index 0000000..2379553
--- /dev/null
+++ b/spake2/src/group.rs
@@ -0,0 +1,58 @@
+//! Group trait.
+
+use alloc::vec::Vec;
+use rand_core::{CryptoRng, RngCore};
+
+/// Group trait.
+// TODO(tarcieri): replace with `group` crate?
+pub trait Group {
+    /// Scalar element
+    type Scalar;
+
+    /// Base field element
+    type Element;
+
+    /// Transcript hash
+    type TranscriptHash;
+
+    /// Name
+    fn name() -> &'static str;
+
+    /// `m` constant
+    fn const_m() -> Self::Element;
+
+    /// `n` constant
+    fn const_n() -> Self::Element;
+
+    /// `s` constant
+    fn const_s() -> Self::Element;
+
+    /// Hash to scalar
+    fn hash_to_scalar(s: &[u8]) -> Self::Scalar;
+
+    /// Generate a random scalar
+    fn random_scalar<T>(cspring: &mut T) -> Self::Scalar
+    where
+        T: RngCore + CryptoRng;
+
+    /// Scalar negation
+    fn scalar_neg(s: &Self::Scalar) -> Self::Scalar;
+
+    /// Convert base field element to bytes
+    fn element_to_bytes(e: &Self::Element) -> Vec<u8>;
+
+    /// Convert bytes to base field element
+    fn bytes_to_element(b: &[u8]) -> Option<Self::Element>;
+
+    /// Length of a base field element
+    fn element_length() -> usize;
+
+    /// Fixed-base scalar multiplication
+    fn basepoint_mult(s: &Self::Scalar) -> Self::Element;
+
+    /// Variable-base scalar multiplication
+    fn scalarmult(e: &Self::Element, s: &Self::Scalar) -> Self::Element;
+
+    /// Group operation
+    fn add(a: &Self::Element, b: &Self::Element) -> Self::Element;
+}