Add Moon's curve25519 using SSE2 (GH #761)

Moon's code is very fast. In fact it is so fast it broke our benchmarks. Moon's code registers 0.00 milliseconds and 0.00 megacycles/operation.

1 files changed, 30 insertions, 10 deletions

diff --git a/donna_32.cpp b/donna_32.cpp
index 6e0fe235..168c9aa6 100644
--- a/donna_32.cpp
+++ b/donna_32.cpp
@@ -965,13 +965,7 @@ ANONYMOUS_NAMESPACE_END
 NAMESPACE_BEGIN(CryptoPP)

 NAMESPACE_BEGIN(Donna)

 

-int curve25519(byte publicKey[32], const byte secretKey[32])

-{

-  const byte basePoint[32] = {9};

-  return curve25519(publicKey, secretKey, basePoint);

-}

-

-int curve25519(byte sharedKey[32], const byte secretKey[32], const byte othersKey[32])

+int curve25519_CXX(byte sharedKey[32], const byte secretKey[32], const byte othersKey[32])

 {

   limb bp[10], x[10], z[11], zmone[10];

   byte e[32];

@@ -979,18 +973,44 @@ int curve25519(byte sharedKey[32], const byte secretKey[32], const byte othersKe
   for (unsigned int i = 0; i < 32; ++i)

     e[i] = secretKey[i];

 

-  e[0] &= 248;

-  e[31] &= 127;

-  e[31] |= 64;

+  // I'd like to remove this copy/clamp but I don't

+  // know if an attacker can cause an information

+  // leak if multiply is misused.

+  e[0] &= 248; e[31] &= 127; e[31] |= 64;

 

   fexpand(bp, othersKey);

   cmult(x, z, e, bp);

   crecip(zmone, z);

   fmul(z, x, zmone);

   fcontract(sharedKey, z);

+

   return 0;

 }

 

+int curve25519(byte publicKey[32], const byte secretKey[32])

+{

+  const byte basePoint[32] = {9};

+

+#if (CRYPTOPP_SSE2_INTRIN_AVAILABLE)

+  if (HasSSE2())

+      return curve25519_SSE2(publicKey, secretKey, basePoint);

+  else

+#endif

+

+  return curve25519_CXX(publicKey, secretKey, basePoint);

+}

+

+int curve25519(byte sharedKey[32], const byte secretKey[32], const byte othersKey[32])

+{

+#if (CRYPTOPP_SSE2_INTRIN_AVAILABLE)

+  if (HasSSE2())

+      return curve25519_SSE2(sharedKey, secretKey, othersKey);

+  else

+#endif

+

+  return curve25519_CXX(sharedKey, secretKey, othersKey);

+}

+

 NAMESPACE_END  // Donna

 NAMESPACE_END  // CryptoPP