From d0daf875978848c3edf65c7b3683a21605f72e64 Mon Sep 17 00:00:00 2001
From: lloyd <lloyd@randombit.net>
Date: Sat, 27 Dec 2014 17:50:57 +0000
Subject: Add Curve25519 based on curve25519-donna by Adam Langley.

This uses only the c64 version from curve25519-donna; on systems that
don't have a native uint128_t type, a donna128 type stands in for just
enough 128-bit operations to satisfy donna.cpp
---
 src/lib/pubkey/curve25519/donna128.h | 116 +++++++++++++++++++++++++++++++++++
 1 file changed, 116 insertions(+)
 create mode 100644 src/lib/pubkey/curve25519/donna128.h

(limited to 'src/lib/pubkey/curve25519/donna128.h')

diff --git a/src/lib/pubkey/curve25519/donna128.h b/src/lib/pubkey/curve25519/donna128.h
new file mode 100644
index 000000000..f2b2d88ea
--- /dev/null
+++ b/src/lib/pubkey/curve25519/donna128.h
@@ -0,0 +1,116 @@
+/*
+* A minimal 128-bit integer type for curve25519-donna
+* (C) 2014 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#ifndef BOTAN_CURVE25519_DONNA128_H__
+#define BOTAN_CURVE25519_DONNA128_H__
+
+#include <botan/mul128.h>
+
+namespace Botan {
+
+class donna128
+   {
+   public:
+      donna128(u64bit ll = 0, u64bit hh = 0) { l = ll; h = hh; }
+
+      donna128(const donna128&) = default;
+      donna128& operator=(const donna128&) = default;
+
+      friend donna128 operator>>(const donna128& x, size_t shift)
+         {
+         donna128 z = x;
+         const u64bit carry = z.h << (64 - shift);
+         z.h = (z.h >> shift);
+         z.l = (z.l >> shift) | carry;
+         return z;
+         }
+
+      friend donna128 operator<<(const donna128& x, size_t shift)
+         {
+         donna128 z = x;
+         const u64bit carry = z.l >> (64 - shift);
+         z.l = (z.l << shift);
+         z.h = (z.h << shift) | carry;
+         return z;
+         }
+
+      friend u64bit operator&(const donna128& x, u64bit mask)
+         {
+         return x.l & mask;
+         }
+
+      u64bit operator&=(u64bit mask)
+         {
+         h = 0;
+         l &= mask;
+         return l;
+         }
+
+      donna128& operator+=(const donna128& x)
+         {
+         l += x.l;
+         h += (l < x.l);
+         h += x.h;
+         return *this;
+         }
+
+      donna128& operator+=(u64bit x)
+         {
+         l += x;
+         h += (l < x);
+         return *this;
+         }
+
+      u64bit lo() const { return l; }
+      u64bit hi() const { return h; }
+   private:
+      u64bit h = 0, l = 0;
+   };
+
+inline donna128 operator*(const donna128& x, u64bit y)
+   {
+   BOTAN_ASSERT(x.hi() == 0, "High 64 bits of donna128 set to zero during multiply");
+
+   u64bit lo = 0, hi = 0;
+   mul64x64_128(x.lo(), y, &lo, &hi);
+   return donna128(lo, hi);
+   }
+
+inline donna128 operator+(const donna128& x, const donna128& y)
+   {
+   donna128 z = x;
+   z += y;
+   return z;
+   }
+
+inline donna128 operator+(const donna128& x, u64bit y)
+   {
+   donna128 z = x;
+   z += y;
+   return z;
+   }
+
+inline donna128 operator|(const donna128& x, const donna128& y)
+   {
+   return donna128(x.lo() | y.lo(), x.hi() | y.hi());
+   }
+
+inline u64bit carry_shift(const donna128& a, size_t shift)
+   {
+   return (a >> shift).lo();
+   }
+
+inline u64bit combine_lower(const donna128 a, size_t s1,
+                            const donna128 b, size_t s2)
+   {
+   donna128 z = (a >> s1) | (b << s2);
+   return z.lo();
+   }
+
+}
+
+#endif
-- 
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