Add signature generation operation classes. Remove sign() from

PK_Signing_Key, though for the moment the class remains because there
are a few pieces of code that use it to detect if signatures are
supported, or for passing to functions in look_pk

2 files changed, 59 insertions, 5 deletions

diff --git a/src/pubkey/dsa/dsa.cpp b/src/pubkey/dsa/dsa.cpp
index 91adb83d4..403243a97 100644
--- a/src/pubkey/dsa/dsa.cpp
+++ b/src/pubkey/dsa/dsa.cpp
@@ -109,4 +109,37 @@ bool DSA_PrivateKey::check_key(RandomNumberGenerator& rng, bool strong) const
    return true;
    }
 
+DSA_Signature_Operation::DSA_Signature_Operation(const DSA_PrivateKey& dsa) :
+   q(dsa.group_q()),
+   x(dsa.get_x()),
+   powermod_g_p(dsa.group_g(), dsa.group_p()),
+   mod_q(dsa.group_q())
+   {
+   }
+
+SecureVector<byte> DSA_Signature_Operation::sign(const byte msg[],
+                                                 u32bit msg_len,
+                                                 RandomNumberGenerator& rng)
+   {
+   rng.add_entropy(msg, msg_len);
+
+   BigInt k;
+   do
+      k.randomize(rng, q.bits());
+   while(k >= q);
+
+   BigInt i(msg, msg_len);
+
+   BigInt r = mod_q.reduce(powermod_g_p(k));
+   BigInt s = mod_q.multiply(inverse_mod(k, q), mul_add(x, r, i));
+
+   if(r.is_zero() || s.is_zero())
+      throw Internal_Error("DSA signature gen failure: r or s was zero");
+
+   SecureVector<byte> output(2*q.bytes());
+   r.binary_encode(output + (output.size() / 2 - r.bytes()));
+   s.binary_encode(output + (output.size() - s.bytes()));
+   return output;
+   }
+
 }
diff --git a/src/pubkey/dsa/dsa.h b/src/pubkey/dsa/dsa.h
index 8caa24b6b..444b3a825 100644
--- a/src/pubkey/dsa/dsa.h
+++ b/src/pubkey/dsa/dsa.h
@@ -9,6 +9,9 @@
 #define BOTAN_DSA_H__
 
 #include <botan/dl_algo.h>
+#include <botan/pk_ops.h>
+#include <botan/reducer.h>
+#include <botan/pow_mod.h>
 #include <botan/dsa_core.h>
 
 namespace Botan {
@@ -51,11 +54,6 @@ class BOTAN_DLL DSA_PrivateKey : public DSA_PublicKey,
                                  public virtual DL_Scheme_PrivateKey
    {
    public:
-      SecureVector<byte> sign(const byte hash[], u32bit hash_len,
-                              RandomNumberGenerator& rng) const;
-
-      bool check_key(RandomNumberGenerator& rng, bool strong) const;
-
       DSA_PrivateKey(const AlgorithmIdentifier& alg_id,
                      const MemoryRegion<byte>& key_bits,
                      RandomNumberGenerator& rng);
@@ -63,6 +61,29 @@ class BOTAN_DLL DSA_PrivateKey : public DSA_PublicKey,
       DSA_PrivateKey(RandomNumberGenerator& rng,
                      const DL_Group& group,
                      const BigInt& private_key = 0);
+
+      bool check_key(RandomNumberGenerator& rng, bool strong) const;
+
+      SecureVector<byte> sign(const byte hash[], u32bit hash_len,
+                              RandomNumberGenerator& rng) const;
+   };
+
+class BOTAN_DLL DSA_Signature_Operation : public PK_Ops::Signature_Operation
+   {
+   public:
+      DSA_Signature_Operation(const DSA_PrivateKey& dsa);
+
+      u32bit message_parts() const { return 2; }
+      u32bit message_part_size() const { return q.bytes(); }
+      u32bit max_input_bits() const { return q.bits(); }
+
+      SecureVector<byte> sign(const byte msg[], u32bit msg_len,
+                              RandomNumberGenerator& rng);
+   private:
+      const BigInt& q;
+      const BigInt& x;
+      Fixed_Base_Power_Mod powermod_g_p;
+      Modular_Reducer mod_q;
    };
 
 }