1 files changed, 30 insertions, 0 deletions
diff --git a/pyecsca/ec/naf.py b/pyecsca/ec/naf.py
new file mode 100644
index 0000000..855ffd1
--- /dev/null
+++ b/pyecsca/ec/naf.py
@@ -0,0 +1,30 @@
+from public import public
+from typing import List
+
+
+@public
+def wnaf(k: int, w: int) -> List[int]:
+    half_width = 2 ** (w - 1)
+    full_width = half_width * 2
+
+    def mods(val: int):
+        val_mod = val % full_width
+        if val_mod > half_width:
+            val_mod -= full_width
+        return val_mod
+
+    result = []
+    while k >= 1:
+        if k & 1:
+            k_val = mods(k)
+            result.insert(0, k_val)
+            k -= k_val
+        else:
+            result.insert(0, 0)
+        k >>= 1
+    return result
+
+
+@public
+def naf(k: int) -> List[int]:
+    return wnaf(k, 2)