Add ECGDSA

1 files changed, 148 insertions, 0 deletions

diff --git a/src/lib/pubkey/ecgdsa/ecgdsa.cpp b/src/lib/pubkey/ecgdsa/ecgdsa.cpp
new file mode 100644
index 000000000..b28e3fe96
--- /dev/null
+++ b/src/lib/pubkey/ecgdsa/ecgdsa.cpp
@@ -0,0 +1,148 @@
+/*
+* ECGDSA (BSI-TR-03111, version 2.0)
+* (C) 2016 René Korthaus
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#include <botan/internal/pk_utils.h>
+#include <botan/ecgdsa.h>
+#include <botan/keypair.h>
+
+namespace Botan {
+
+bool ECGDSA_PrivateKey::check_key(RandomNumberGenerator& rng,
+                                 bool strong) const
+   {
+   if(!public_point().on_the_curve())
+      return false;
+
+   if(!strong)
+      return true;
+
+   return KeyPair::signature_consistency_check(rng, *this, "EMSA1(SHA-1)");
+   }
+
+namespace {
+
+/**
+* ECGDSA signature operation
+*/
+class ECGDSA_Signature_Operation : public PK_Ops::Signature_with_EMSA
+   {
+   public:
+      typedef ECGDSA_PrivateKey Key_Type;
+
+      ECGDSA_Signature_Operation(const ECGDSA_PrivateKey& ecgdsa,
+                                const std::string& emsa) :
+         PK_Ops::Signature_with_EMSA(emsa),
+         m_order(ecgdsa.domain().get_order()),
+         m_base_point(ecgdsa.domain().get_base_point(), m_order),
+         m_x(ecgdsa.private_value()),
+         m_mod_order(m_order)
+         {
+         }
+
+      secure_vector<byte> raw_sign(const byte msg[], size_t msg_len,
+                                   RandomNumberGenerator& rng) override;
+
+      size_t message_parts() const override { return 2; }
+      size_t message_part_size() const override { return m_order.bytes(); }
+      size_t max_input_bits() const override { return m_order.bits(); }
+
+   private:
+      const BigInt& m_order;
+      Blinded_Point_Multiply m_base_point;
+      const BigInt& m_x;
+      Modular_Reducer m_mod_order;
+   };
+
+secure_vector<byte>
+ECGDSA_Signature_Operation::raw_sign(const byte msg[], size_t msg_len,
+                                     RandomNumberGenerator& rng)
+   {
+   const BigInt m(msg, msg_len);
+
+   BigInt k = BigInt::random_integer(rng, 1, m_order);
+
+   const PointGFp k_times_P = m_base_point.blinded_multiply(k, rng);
+   const BigInt r = m_mod_order.reduce(k_times_P.get_affine_x());
+   const BigInt s = m_mod_order.multiply(m_x, mul_sub(k, r, m));
+
+   // With overwhelming probability, a bug rather than actual zero r/s
+   BOTAN_ASSERT(s != 0, "invalid s");
+   BOTAN_ASSERT(r != 0, "invalid r");
+
+   secure_vector<byte> output(2*m_order.bytes());
+   r.binary_encode(&output[output.size() / 2 - r.bytes()]);
+   s.binary_encode(&output[output.size() - s.bytes()]);
+   return output;
+   }
+
+/**
+* ECGDSA verification operation
+*/
+class ECGDSA_Verification_Operation : public PK_Ops::Verification_with_EMSA
+   {
+   public:
+      typedef ECGDSA_PublicKey Key_Type;
+
+      ECGDSA_Verification_Operation(const ECGDSA_PublicKey& ecgdsa,
+                                   const std::string& emsa) :
+         PK_Ops::Verification_with_EMSA(emsa),
+         m_base_point(ecgdsa.domain().get_base_point()),
+         m_public_point(ecgdsa.public_point()),
+         m_order(ecgdsa.domain().get_order()),
+         m_mod_order(m_order)
+         {
+         }
+
+      size_t message_parts() const override { return 2; }
+      size_t message_part_size() const override { return m_order.bytes(); }
+      size_t max_input_bits() const override { return m_order.bits(); }
+
+      bool with_recovery() const override { return false; }
+
+      bool verify(const byte msg[], size_t msg_len,
+                  const byte sig[], size_t sig_len) override;
+   private:
+      const PointGFp& m_base_point;
+      const PointGFp& m_public_point;
+      const BigInt& m_order;
+      // FIXME: should be offered by curve
+      Modular_Reducer m_mod_order;
+   };
+
+bool ECGDSA_Verification_Operation::verify(const byte msg[], size_t msg_len,
+                                           const byte sig[], size_t sig_len)
+   {
+   if(sig_len != m_order.bytes()*2)
+      return false;
+
+   BigInt e(msg, msg_len);
+
+   BigInt r(sig, sig_len / 2);
+   BigInt s(sig + sig_len / 2, sig_len / 2);
+
+   if(r <= 0 || r >= m_order || s <= 0 || s >= m_order)
+      return false;
+
+   BigInt w = inverse_mod(r, m_order);
+
+   const BigInt u1 = m_mod_order.reduce(e * w);
+   const BigInt u2 = m_mod_order.reduce(s * w);
+   const PointGFp R = multi_exponentiate(m_base_point, u1, m_public_point, u2);
+
+   if(R.is_zero())
+      return false;
+
+   const BigInt v = m_mod_order.reduce(R.get_affine_x());
+   return (v == r);
+   }
+
+BOTAN_REGISTER_PK_SIGNATURE_OP("ECGDSA", ECGDSA_Signature_Operation);
+BOTAN_REGISTER_PK_VERIFY_OP("ECGDSA", ECGDSA_Verification_Operation);
+
+}
+
+}