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.

1 files changed, 26 insertions, 7 deletions

diff --git a/src/pubkey/dh/dh.h b/src/pubkey/dh/dh.h
index 14bc916a7..318a6215c 100644
--- a/src/pubkey/dh/dh.h
+++ b/src/pubkey/dh/dh.h
@@ -9,7 +9,8 @@
 #define BOTAN_DIFFIE_HELLMAN_H__
 
 #include <botan/dl_algo.h>
-#include <botan/dh_core.h>
+#include <botan/pow_mod.h>
+#include <botan/pk_ops.h>
 
 namespace Botan {
 
@@ -22,7 +23,7 @@ class BOTAN_DLL DH_PublicKey : public virtual DL_Scheme_PublicKey
       std::string algo_name() const { return "DH"; }
 
       MemoryVector<byte> public_value() const;
-      u32bit max_input_bits() const;
+      u32bit max_input_bits() const { return group_p().bits(); }
 
       DL_Group::Format group_format() const { return DL_Group::ANSI_X9_42; }
 
@@ -48,10 +49,6 @@ class BOTAN_DLL DH_PrivateKey : public DH_PublicKey,
                                 public virtual DL_Scheme_PrivateKey
    {
    public:
-      SecureVector<byte> derive_key(const byte other[], u32bit length) const;
-      SecureVector<byte> derive_key(const DH_PublicKey& other) const;
-      SecureVector<byte> derive_key(const BigInt& other) const;
-
       MemoryVector<byte> public_value() const;
 
       /**
@@ -72,8 +69,30 @@ class BOTAN_DLL DH_PrivateKey : public DH_PublicKey,
       */
       DH_PrivateKey(RandomNumberGenerator& rng, const DL_Group& grp,
                     const BigInt& x = 0);
+   };
+
+/**
+* DH operation
+*/
+class BOTAN_DLL DH_KA_Operation : public PK_Ops::KA_Operation
+   {
+   public:
+
+      DH_KA_Operation(const DH_PrivateKey& key) :
+         powermod_x_p(key.get_x(), key.get_domain().get_p()),
+         p_bytes(key.get_domain().get_p().bytes())
+         {}
+
+      SecureVector<byte> agree(const byte w[], u32bit w_len) const
+         {
+         return BigInt::encode_1363(
+            powermod_x_p(BigInt::decode(w, w_len)),
+            p_bytes);
+         }
+
    private:
-      DH_Core core;
+      Fixed_Exponent_Power_Mod powermod_x_p;
+      u32bit p_bytes;
    };
 
 }