propagate from branch 'net.randombit.botan' (head fc86fc4842254088bf820ea6ebf05877aa63fb22)

            to branch 'net.randombit.botan.c++0x' (head 77565ff7252df7f8faad86d65075498b0adb93d8)

1 files changed, 51 insertions, 0 deletions

diff --git a/src/pubkey/ecdh/ecdh.cpp b/src/pubkey/ecdh/ecdh.cpp
new file mode 100644
index 000000000..7577a8569
--- /dev/null
+++ b/src/pubkey/ecdh/ecdh.cpp
@@ -0,0 +1,51 @@
+/*
+* ECDH implemenation
+* (C) 2007 Manuel Hartl, FlexSecure GmbH
+*     2007 Falko Strenzke, FlexSecure GmbH
+*     2008-2010 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/ecdh.h>
+
+namespace Botan {
+
+/**
+* Derive a key
+*/
+SecureVector<byte> ECDH_PrivateKey::derive_key(const byte key[],
+                                               u32bit key_len) const
+   {
+   MemoryVector<byte> key_x(key, key_len); // FIXME: nasty/slow
+   PointGFp point = OS2ECP(key_x, public_point().get_curve());
+
+   return derive_key(point);
+   }
+
+/**
+* Derive a key
+*/
+SecureVector<byte> ECDH_PrivateKey::derive_key(const ECDH_PublicKey& key) const
+   {
+   return derive_key(key.public_point());
+   }
+
+/**
+* Derive a key
+*/
+SecureVector<byte> ECDH_PrivateKey::derive_key(const PointGFp& point) const
+   {
+   const BigInt& cofactor = domain().get_cofactor();
+   const BigInt& n = domain().get_order();
+
+   BigInt l = inverse_mod(cofactor, n); // can precompute this
+
+   PointGFp S = (cofactor * point) * (private_value() * l);
+   S.check_invariants();
+
+   return BigInt::encode_1363(S.get_affine_x(),
+                              point.get_curve().get_p().bytes());
+   }
+
+}