1 files changed, 117 insertions, 0 deletions
diff --git a/src/test/slownacl_curve25519.py b/src/test/slownacl_curve25519.py
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+++ b/src/test/slownacl_curve25519.py
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+# This is the curve25519 implementation from Matthew Dempsky's "Slownacl"
+# library.  It is in the public domain.
+#
+# It isn't constant-time.  Don't use it except for testing.
+#
+# Nick got the slownacl source from:
+#        https://github.com/mdempsky/dnscurve/tree/master/slownacl
+
+__all__ = ['smult_curve25519_base', 'smult_curve25519']
+
+import sys
+
+P = 2 ** 255 - 19
+A = 486662
+
+def expmod(b, e, m):
+  if e == 0: return 1
+  t = expmod(b, e // 2, m) ** 2 % m
+  if e & 1: t = (t * b) % m
+  return t
+
+def inv(x):
+  return expmod(x, P - 2, P)
+
+# Addition and doubling formulas taken from Appendix D of "Curve25519:
+# new Diffie-Hellman speed records".
+
+def add(n,m,d):
+  (xn,zn), (xm,zm), (xd,zd) = n, m, d
+  x = 4 * (xm * xn - zm * zn) ** 2 * zd
+  z = 4 * (xm * zn - zm * xn) ** 2 * xd
+  return (x % P, z % P)
+
+def double(n):
+  (xn,zn) = n
+  x = (xn ** 2 - zn ** 2) ** 2
+  z = 4 * xn * zn * (xn ** 2 + A * xn * zn + zn ** 2)
+  return (x % P, z % P)
+
+def curve25519(n, base):
+  one = (base,1)
+  two = double(one)
+  # f(m) evaluates to a tuple containing the mth multiple and the
+  # (m+1)th multiple of base.
+  def f(m):
+    if m == 1: return (one, two)
+    (pm, pm1) = f(m // 2)
+    if (m & 1):
+      return (add(pm, pm1, one), double(pm1))
+    return (double(pm), add(pm, pm1, one))
+  ((x,z), _) = f(n)
+  return (x * inv(z)) % P
+
+if sys.version < '3':
+    def b2i(c):
+        return ord(c)
+    def i2b(i):
+        return chr(i)
+    def ba2bs(ba):
+        return "".join(ba)
+else:
+    def b2i(c):
+        return c
+    def i2b(i):
+        return i
+    def ba2bs(ba):
+        return bytes(ba)
+
+def unpack(s):
+  if len(s) != 32: raise ValueError('Invalid Curve25519 argument')
+  return sum(b2i(s[i]) << (8 * i) for i in range(32))
+
+def pack(n):
+  return ba2bs([i2b((n >> (8 * i)) & 255) for i in range(32)])
+
+def clamp(n):
+  n &= ~7
+  n &= ~(128 << 8 * 31)
+  n |= 64 << 8 * 31
+  return n
+
+def smult_curve25519(n, p):
+  n = clamp(unpack(n))
+  p = unpack(p)
+  return pack(curve25519(n, p))
+
+def smult_curve25519_base(n):
+  n = clamp(unpack(n))
+  return pack(curve25519(n, 9))
+
+
+#
+# This part I'm adding in for compatibility with the curve25519 python
+# module. -Nick
+#
+import os
+
+class Private:
+    def __init__(self, secret=None, seed=None):
+        self.private = pack(clamp(unpack(os.urandom(32))))
+
+    def get_public(self):
+        return Public(smult_curve25519_base(self.private))
+
+    def get_shared_key(self, public, hashfn):
+        return hashfn(smult_curve25519(self.private, public.public))
+
+    def serialize(self):
+        return self.private
+
+class Public:
+    def __init__(self, public):
+        self.public = public
+
+    def serialize(self):
+        return self.public
+