This checkin represents a pretty major change in how PK operations are

performed. Up until now, each key object (eg DSA_PublicKey or
ECDH_PrivateKey) had two jobs: contain the key material, and know how
to perform any operations on that key.  However because of a desire to
support alternative implementations (GNU MP, hardware, whatever),
there was a notion of operations, with the key objects containing an
op that they got via engine rather than actually implementing the
underlying algorithms directly.

Now, represent the operation as an abstract interface (typically
mapping a byte string to a byte string), and pass a plain Public_Key&
or Private_Key& to the engine. The engine does any checks it wants (eg
based on name, typeid, key sizes, etc), and either returns nothing
(I'll pass) or a pointer to a new operation that represents signatures
or encryption or what-have-you using that key.

This means that plain key objects no longer contain operations.  This
is a major break with the traditional interface. On the other hand,
using these 'bare' operations without padding, KDFs, etc is 99% of the
time a bad idea anyway (and if you really need them, there are options
so you get the bare op but via the pubkey.h interfaces).

Currently this change is only implemented for DH and ECDH (ie, key
agreement algorithms). Additionally the optional engines (gnump and
openssl) have not been updated. I'll probably wait to touch those
until after I can change them all in one go for all algos.

2 files changed, 37 insertions, 1 deletions

diff --git a/src/pubkey/ecdh/ecdh.cpp b/src/pubkey/ecdh/ecdh.cpp
index 7ecc40ae4..37dc7c392 100644
--- a/src/pubkey/ecdh/ecdh.cpp
+++ b/src/pubkey/ecdh/ecdh.cpp
@@ -11,6 +11,27 @@
 
 namespace Botan {
 
+ECDH_KA_Operation::ECDH_KA_Operation(const ECDH_PrivateKey& key)
+   {
+   cofactor = key.domain().get_cofactor();
+
+   curve = key.domain().get_curve();
+
+   l_times_priv = inverse_mod(cofactor, key.domain().get_order()) *
+                  key.private_value();
+   }
+
+SecureVector<byte> ECDH_KA_Operation::agree(const byte w[], u32bit w_len) const
+   {
+   PointGFp point = OS2ECP(w, w_len, curve);
+
+   PointGFp S = (cofactor * point) * l_times_priv;
+   S.check_invariants();
+
+   return BigInt::encode_1363(S.get_affine_x(),
+                              curve.get_p().bytes());
+   }
+
 /**
 * Derive a key
 */
diff --git a/src/pubkey/ecdh/ecdh.h b/src/pubkey/ecdh/ecdh.h
index 8185e25f2..ad7efdc13 100644
--- a/src/pubkey/ecdh/ecdh.h
+++ b/src/pubkey/ecdh/ecdh.h
@@ -11,6 +11,7 @@
 #define BOTAN_ECDH_KEY_H__
 
 #include <botan/ecc_key.h>
+#include <botan/pk_ops.h>
 
 namespace Botan {
 
@@ -75,7 +76,7 @@ class BOTAN_DLL ECDH_PrivateKey : public ECDH_PublicKey,
 
       MemoryVector<byte> public_value() const
          { return EC2OSP(public_point(), PointGFp::UNCOMPRESSED); }
-
+   private:
       /**
       * Derive a shared key with the other parties public key.
       * @param key the other partys public key
@@ -96,6 +97,20 @@ class BOTAN_DLL ECDH_PrivateKey : public ECDH_PublicKey,
       SecureVector<byte> derive_key(const PointGFp& point) const;
    };
 
+/**
+* ECDH operation
+*/
+class BOTAN_DLL ECDH_KA_Operation : public PK_Ops::KA_Operation
+   {
+   public:
+      ECDH_KA_Operation(const ECDH_PrivateKey& key);
+
+      SecureVector<byte> agree(const byte w[], u32bit w_len) const;
+   private:
+      CurveGFp curve;
+      BigInt l_times_priv, cofactor;
+   };
+
 }
 
 #endif