Add Twisted Edwards curve point arithmetic

Author: tomato42

src/ecdsa/eddsa.py

@@ -0,0 +1,62 @@
+"""Implementation of Edwards Digital Signature Algorithm."""
+
+from . import ellipticcurve
+from ._compat import remove_whitespace
+
+# edwards25519, defined in RFC7748
+_p = 2 ** 255 - 19
+_a = -1
+_d = int(
+    remove_whitespace(
+        "370957059346694393431380835087545651895421138798432190163887855330"
+        "85940283555"
+    )
+)
+_h = 8
+
+_Gx = int(
+    remove_whitespace(
+        "151122213495354007725011514095885315114540126930418572060461132"
+        "83949847762202"
+    )
+)
+_Gy = int(
+    remove_whitespace(
+        "463168356949264781694283940034751631413079938662562256157830336"
+        "03165251855960"
+    )
+)
+_r = 2 ** 252 + 0x14DEF9DEA2F79CD65812631A5CF5D3ED
+
+curve_ed25519 = ellipticcurve.CurveEdTw(_p, _a, _d, _h)
+generator_ed25519 = ellipticcurve.PointEdwards(
+    curve_ed25519, _Gx, _Gy, 1, _Gx * _Gy % _p, _r
+)
+
+
+# edwards448, defined in RFC7748
+_p = 2 ** 448 - 2 ** 224 - 1
+_a = 1
+_d = -39081 % _p
+_h = 4
+
+_Gx = int(
+    remove_whitespace(
+        "224580040295924300187604334099896036246789641632564134246125461"
+        "686950415467406032909029192869357953282578032075146446173674602635"
+        "247710"
+    )
+)
+_Gy = int(
+    remove_whitespace(
+        "298819210078481492676017930443930673437544040154080242095928241"
+        "372331506189835876003536878655418784733982303233503462500531545062"
+        "832660"
+    )
+)
+_r = 2 ** 446 - 0x8335DC163BB124B65129C96FDE933D8D723A70AADC873D6D54A7BB0D
+
+curve_ed448 = ellipticcurve.CurveEdTw(_p, _a, _d, _h)
+generator_ed448 = ellipticcurve.PointEdwards(
+    curve_ed448, _Gx, _Gy, 1, _Gx * _Gy % _p, _r
+)