1 files changed, 81 insertions, 0 deletions
diff --git a/src/pubkey/dsa/dsa_op.cpp b/src/pubkey/dsa/dsa_op.cpp
new file mode 100644
index 000000000..8b6e5403b
--- /dev/null
+++ b/src/pubkey/dsa/dsa_op.cpp
@@ -0,0 +1,81 @@
+/*************************************************
+* DSA Operations Source File                     *
+* (C) 1999-2007 Jack Lloyd                       *
+*************************************************/
+
+#include <botan/dsa_op.h>
+#include <botan/eng_def.h>
+
+namespace Botan {
+
+/*************************************************
+* Default_DSA_Op Constructor                     *
+*************************************************/
+Default_DSA_Op::Default_DSA_Op(const DL_Group& grp, const BigInt& y1,
+                               const BigInt& x1) : x(x1), y(y1), group(grp)
+   {
+   powermod_g_p = Fixed_Base_Power_Mod(group.get_g(), group.get_p());
+   powermod_y_p = Fixed_Base_Power_Mod(y, group.get_p());
+   mod_p = Modular_Reducer(group.get_p());
+   mod_q = Modular_Reducer(group.get_q());
+   }
+
+/*************************************************
+* Default DSA Verify Operation                   *
+*************************************************/
+bool Default_DSA_Op::verify(const byte msg[], u32bit msg_len,
+                            const byte sig[], u32bit sig_len) const
+   {
+   const BigInt& q = group.get_q();
+
+   if(sig_len != 2*q.bytes() || msg_len > q.bytes())
+      return false;
+
+   BigInt r(sig, q.bytes());
+   BigInt s(sig + q.bytes(), q.bytes());
+   BigInt i(msg, msg_len);
+
+   if(r <= 0 || r >= q || s <= 0 || s >= q)
+      return false;
+
+   s = inverse_mod(s, q);
+   s = mod_p.multiply(powermod_g_p(mod_q.multiply(s, i)),
+                      powermod_y_p(mod_q.multiply(s, r)));
+
+   return (mod_q.reduce(s) == r);
+   }
+
+/*************************************************
+* Default DSA Sign Operation                     *
+*************************************************/
+SecureVector<byte> Default_DSA_Op::sign(const byte in[], u32bit length,
+                                        const BigInt& k) const
+   {
+   if(x == 0)
+      throw Internal_Error("Default_DSA_Op::sign: No private key");
+
+   const BigInt& q = group.get_q();
+   BigInt i(in, length);
+
+   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("Default_DSA_Op::sign: 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;
+   }
+
+/*************************************************
+* Acquire a DSA op                               *
+*************************************************/
+DSA_Operation* Default_Engine::dsa_op(const DL_Group& group, const BigInt& y,
+                                      const BigInt& x) const
+   {
+   return new Default_DSA_Op(group, y, x);
+   }
+
+}