1 files changed, 136 insertions, 0 deletions
diff --git a/src/pubkey/ecdsa/ecdsa_op.cpp b/src/pubkey/ecdsa/ecdsa_op.cpp
new file mode 100644
index 000000000..58f00cb4b
--- /dev/null
+++ b/src/pubkey/ecdsa/ecdsa_op.cpp
@@ -0,0 +1,136 @@
+/*************************************************
+* ECDSA Operation                                *
+* (C) 2007 FlexSecure GmbH                       *
+*     2008 Jack Lloyd                            *
+*************************************************/
+
+#include <botan/eng_def.h>
+
+namespace Botan {
+
+bool Default_ECDSA_Op::verify(const byte signature[], u32bit sig_len,
+                              const byte message[], u32bit mess_len) const
+   {
+   if(sig_len % 2 != 0)
+      throw Invalid_Argument("Erroneous length of signature");
+
+   //NOTE: it is not checked whether the public point is set
+   if(m_dom_pars.get_curve().get_p() == 0)
+      throw Internal_Error("domain parameters not set");
+
+   BigInt e(message, mess_len);
+
+   u32bit rs_len = sig_len/2;
+   SecureVector<byte> sv_r;
+   SecureVector<byte> sv_s;
+   sv_r.set(signature, rs_len);
+   sv_s.set(signature+rs_len, rs_len);
+   BigInt r = BigInt::decode ( sv_r, sv_r.size());
+   BigInt s = BigInt::decode (sv_s, sv_s.size());
+
+   if(r < 0 || r >= m_dom_pars.get_order())
+      throw Invalid_Argument("r in ECDSA signature has an illegal value");
+
+   if(s < 0 || s >= m_dom_pars.get_order())
+      throw Invalid_Argument("s in ECDSA signature has an illegal value");
+
+   BigInt w = inverse_mod(s, m_dom_pars.get_order());
+
+   PointGFp R = w*(e*m_dom_pars.get_base_point() + r*m_pub_key);
+   if(R.is_zero())
+      return false;
+
+   BigInt x = R.get_affine_x().get_value();
+   bool result = (x % m_dom_pars.get_order() == r);
+   return result;
+   }
+
+SecureVector<byte> Default_ECDSA_Op::sign(const byte message[],
+                                          u32bit mess_len,
+                                          RandomNumberGenerator& rng) const
+   {
+   if(m_priv_key == 0)
+      throw Internal_Error("Default_ECDSA_Op::sign(): no private key");
+
+   if(m_dom_pars.get_curve().get_p() == 0)
+      throw Internal_Error("Default_ECDSA_Op::sign(): domain parameters not set");
+
+   BigInt e(message, mess_len);
+
+   // generate k
+   BigInt k;
+   BigInt r(0);
+   const BigInt n(m_dom_pars.get_order());
+   while(r == 0)
+      {
+      k = BigInt::random_integer(rng, 1, n);
+
+      PointGFp k_times_P(m_dom_pars.get_base_point());
+      k_times_P.mult_this_secure(k, n, n-1);
+      k_times_P.check_invariants();
+      r =  k_times_P.get_affine_x().get_value() % n;
+      }
+   BigInt k_inv = inverse_mod(k, n);
+
+   // use randomization against attacks on s:
+   // a = k_inv * (r*(d + x) + e) mod n
+   // b = k_inv * r * x mod n
+   // s = a - b mod n
+   // where x is a random integer
+
+#ifdef CMS_RAND
+   BigInt x = Botan::random_integer(0, n);
+   BigInt s = m_priv_key + x; // obscure the secret from the beginning
+   // all following operations thus are randomized
+   s *= r;
+   s += e;
+   s *= k_inv;
+   s %= n;
+
+   BigInt b = x; // again, start with the random number
+   b *= r;
+   b *= k_inv;
+   b %= n;
+   s -= b; // s = a - b
+   if(s <= 0) // s %= n
+      {
+      s += n;
+      }
+#else // CMS_RAND
+   // no countermeasure here
+   BigInt s(r);
+   s *= m_priv_key;
+   s += e;
+   s *= k_inv;
+   s %= n;
+
+#endif // CMS_RAND
+
+   SecureVector<byte> sv_r = BigInt::encode_1363 ( r, m_dom_pars.get_order().bytes() );
+   SecureVector<byte> sv_s = BigInt::encode_1363 ( s, m_dom_pars.get_order().bytes() );
+
+   SecureVector<byte> result(sv_r);
+   result.append(sv_s);
+   return result;
+   }
+
+Default_ECDSA_Op::Default_ECDSA_Op(const EC_Domain_Params& dom_pars, const BigInt& priv_key, const PointGFp& pub_key)
+   : m_dom_pars(dom_pars),
+     m_pub_key(pub_key),
+     m_priv_key(priv_key)
+   {
+
+   }
+
+/*************************************************
+* Acquire a ECDSA op                             *
+*************************************************/
+ECDSA_Operation* Default_Engine::ecdsa_op(const EC_Domain_Params& dom_pars,
+                                          const BigInt& priv_key,
+                                          const PointGFp& pub_key) const
+   {
+   return new Default_ECDSA_Op(dom_pars, priv_key, pub_key);
+   }
+
+}
+