1 files changed, 21 insertions, 29 deletions
diff --git a/src/pubkey/eckaeg/eckaeg.cpp b/src/pubkey/eckaeg/eckaeg.cpp
index 639060f33..95b5afdbb 100644
--- a/src/pubkey/eckaeg/eckaeg.cpp
+++ b/src/pubkey/eckaeg/eckaeg.cpp
@@ -2,47 +2,23 @@
 * ECKAEG implemenation
 * (C) 2007 Manuel Hartl, FlexSecure GmbH
 *     2007 Falko Strenzke, FlexSecure GmbH
-*     2008 Jack Lloyd
+*     2008-2010 Jack Lloyd
 *
 * Distributed under the terms of the Botan license
 */
 
 #include <botan/eckaeg.h>
-#include <botan/numthry.h>
-#include <botan/der_enc.h>
-#include <botan/ber_dec.h>
-#include <botan/secmem.h>
-#include <botan/point_gfp.h>
 
 namespace Botan {
 
-void ECKAEG_PublicKey::X509_load_hook()
-   {
-   EC_PublicKey::X509_load_hook();
-   m_eckaeg_core = ECKAEG_Core(domain(), 0, public_point());
-   }
-
 ECKAEG_PublicKey::ECKAEG_PublicKey(const EC_Domain_Params& dom_par,
                                    const PointGFp& pub_point)
    {
    domain_params = dom_par;
    public_key = pub_point;
 
-   if(domain().get_curve() != pub_point.get_curve())
+   if(domain().get_curve() != public_point().get_curve())
       throw Invalid_Argument("ECKAEG_PublicKey: curve mismatch in constructor");
-
-   m_eckaeg_core = ECKAEG_Core(domain(), 0, public_point());
-   }
-
-void ECKAEG_PrivateKey::PKCS8_load_hook(bool generated)
-   {
-   EC_PrivateKey::PKCS8_load_hook(generated);
-   m_eckaeg_core = ECKAEG_Core(domain(), private_value(), public_point());
-   }
-
-MemoryVector<byte> ECKAEG_PrivateKey::public_value() const
-   {
-   return EC2OSP(public_point(), PointGFp::UNCOMPRESSED);
    }
 
 ECKAEG_PrivateKey::ECKAEG_PrivateKey(RandomNumberGenerator& rng,
@@ -50,7 +26,6 @@ ECKAEG_PrivateKey::ECKAEG_PrivateKey(RandomNumberGenerator& rng,
    {
    domain_params = dom_pars;
    generate_private_key(rng);
-   m_eckaeg_core = ECKAEG_Core(domain(), private_value(), public_point());
    }
 
 /**
@@ -62,7 +37,7 @@ SecureVector<byte> ECKAEG_PrivateKey::derive_key(const byte key[],
    MemoryVector<byte> key_x(key, key_len); // FIXME: nasty/slow
    PointGFp point = OS2ECP(key_x, public_point().get_curve());
 
-   return m_eckaeg_core.agree(point);
+   return derive_key(point);
    }
 
 /**
@@ -70,7 +45,24 @@ SecureVector<byte> ECKAEG_PrivateKey::derive_key(const byte key[],
 */
 SecureVector<byte> ECKAEG_PrivateKey::derive_key(const ECKAEG_PublicKey& key) const
    {
-   return m_eckaeg_core.agree(key.public_point());
+   return derive_key(key.public_point());
+   }
+
+/**
+* Derive a key
+*/
+SecureVector<byte> ECKAEG_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());
    }
 
 }