Add precomputation length

dalek-cryptography · Aug 3, 2024 · b311796 · b311796
1 parent 0964f80
commit b311796
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diff --git a/curve25519-dalek/src/backend/mod.rs b/curve25519-dalek/src/backend/mod.rs
@@ -128,6 +128,18 @@ impl VartimePrecomputedStraus {
         }
     }
 
+    pub fn len(&self) -> usize {
+        use crate::traits::VartimePrecomputedMultiscalarMul;
+
+        match self {
+            #[cfg(curve25519_dalek_backend = "simd")]
+            VartimePrecomputedStraus::Avx2(inner) => inner.len(),
+            #[cfg(all(curve25519_dalek_backend = "simd", nightly))]
+            VartimePrecomputedStraus::Avx512ifma(inner) => inner.len(),
+            VartimePrecomputedStraus::Scalar(inner) => inner.len(),
+        }
+    }
+
     pub fn optional_mixed_multiscalar_mul<I, J, K>(
         &self,
         static_scalars: I,

diff --git a/curve25519-dalek/src/backend/serial/scalar_mul/precomputed_straus.rs b/curve25519-dalek/src/backend/serial/scalar_mul/precomputed_straus.rs
@@ -46,6 +46,10 @@ impl VartimePrecomputedMultiscalarMul for VartimePrecomputedStraus {
         }
     }
 
+    fn len(&self) -> usize {
+        self.static_lookup_tables.len()
+    }
+
     fn optional_mixed_multiscalar_mul<I, J, K>(
         &self,
         static_scalars: I,

diff --git a/curve25519-dalek/src/backend/vector/scalar_mul/precomputed_straus.rs b/curve25519-dalek/src/backend/vector/scalar_mul/precomputed_straus.rs
@@ -54,6 +54,10 @@ pub mod spec {
             }
         }
 
+        fn len(&self) -> usize {
+            self.static_lookup_tables.len()
+        }
+
         fn optional_mixed_multiscalar_mul<I, J, K>(
             &self,
             static_scalars: I,

diff --git a/curve25519-dalek/src/edwards.rs b/curve25519-dalek/src/edwards.rs
@@ -879,6 +879,10 @@ impl VartimePrecomputedMultiscalarMul for VartimeEdwardsPrecomputation {
         Self(crate::backend::VartimePrecomputedStraus::new(static_points))
     }
 
+    fn len(&self) -> usize {
+        self.0.len()
+    }
+
     fn optional_mixed_multiscalar_mul<I, J, K>(
         &self,
         static_scalars: I,
@@ -2136,6 +2140,8 @@ mod test {
 
         let precomputation = VartimeEdwardsPrecomputation::new(static_points.iter());
 
+        assert_eq!(precomputation.len(), 128);
+
         let P = precomputation.vartime_mixed_multiscalar_mul(
             &static_scalars,
             &dynamic_scalars,

diff --git a/curve25519-dalek/src/ristretto.rs b/curve25519-dalek/src/ristretto.rs
@@ -1027,6 +1027,10 @@ impl VartimePrecomputedMultiscalarMul for VartimeRistrettoPrecomputation {
         ))
     }
 
+    fn len(&self) -> usize {
+        self.0.len()
+    }
+
     fn optional_mixed_multiscalar_mul<I, J, K>(
         &self,
         static_scalars: I,
@@ -1852,6 +1856,8 @@ mod test {
 
         let precomputation = VartimeRistrettoPrecomputation::new(static_points.iter());
 
+        assert_eq!(precomputation.len(), 128);
+
         let P = precomputation.vartime_mixed_multiscalar_mul(
             &static_scalars,
             &dynamic_scalars,

diff --git a/curve25519-dalek/src/traits.rs b/curve25519-dalek/src/traits.rs
@@ -299,6 +299,9 @@ pub trait VartimePrecomputedMultiscalarMul: Sized {
         I: IntoIterator,
         I::Item: Borrow<Self::Point>;
 
+    /// Return the number of static points in the precomputation.
+    fn len(&self) -> usize;
+
     /// Given `static_scalars`, an iterator of public scalars
     /// \\(b_i\\), compute
     /// $$