Botan  2.8.0
Crypto and TLS for C++11
ecdh.cpp
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1 /*
2 * ECDH implemenation
3 * (C) 2007 Manuel Hartl, FlexSecure GmbH
4 * 2007 Falko Strenzke, FlexSecure GmbH
5 * 2008-2010 Jack Lloyd
6 *
7 * Botan is released under the Simplified BSD License (see license.txt)
8 */
9 
10 #include <botan/ecdh.h>
11 #include <botan/numthry.h>
12 #include <botan/internal/pk_ops_impl.h>
13 
14 #if defined(BOTAN_HAS_OPENSSL)
15  #include <botan/internal/openssl.h>
16 #endif
17 
18 namespace Botan {
19 
20 namespace {
21 
22 /**
23 * ECDH operation
24 */
25 class ECDH_KA_Operation final : public PK_Ops::Key_Agreement_with_KDF
26  {
27  public:
28 
29  ECDH_KA_Operation(const ECDH_PrivateKey& key, const std::string& kdf, RandomNumberGenerator& rng) :
30  PK_Ops::Key_Agreement_with_KDF(kdf),
31  m_group(key.domain()),
32  m_rng(rng)
33  {
34  m_l_times_priv = m_group.inverse_mod_order(m_group.get_cofactor()) * key.private_value();
35  }
36 
37  size_t agreed_value_size() const override { return m_group.get_p_bytes(); }
38 
39  secure_vector<uint8_t> raw_agree(const uint8_t w[], size_t w_len) override
40  {
41  PointGFp input_point = m_group.get_cofactor() * m_group.OS2ECP(w, w_len);
42  input_point.randomize_repr(m_rng);
43 
44  const PointGFp S = m_group.blinded_var_point_multiply(
45  input_point, m_l_times_priv, m_rng, m_ws);
46 
47  if(S.on_the_curve() == false)
48  throw Internal_Error("ECDH agreed value was not on the curve");
49  return BigInt::encode_1363(S.get_affine_x(), m_group.get_p_bytes());
50  }
51  private:
52  const EC_Group m_group;
53  BigInt m_l_times_priv;
54  RandomNumberGenerator& m_rng;
55  std::vector<BigInt> m_ws;
56  };
57 
58 }
59 
60 std::unique_ptr<PK_Ops::Key_Agreement>
62  const std::string& params,
63  const std::string& provider) const
64  {
65 #if defined(BOTAN_HAS_OPENSSL)
66  if(provider == "openssl" || provider.empty())
67  {
68  try
69  {
70  return make_openssl_ecdh_ka_op(*this, params);
71  }
72  catch(Lookup_Error&)
73  {
74  if(provider == "openssl")
75  throw;
76  }
77  }
78 #endif
79 
80  if(provider == "base" || provider.empty())
81  return std::unique_ptr<PK_Ops::Key_Agreement>(new ECDH_KA_Operation(*this, params, rng));
82 
83  throw Provider_Not_Found(algo_name(), provider);
84  }
85 
86 
87 }
int(* final)(unsigned char *, CTX *)
std::unique_ptr< PK_Ops::Key_Agreement > create_key_agreement_op(RandomNumberGenerator &rng, const std::string &params, const std::string &provider) const override
Definition: ecdh.cpp:61
Definition: alg_id.cpp:13
std::string algo_name() const override
Definition: ecdh.h:45
static secure_vector< uint8_t > encode_1363(const BigInt &n, size_t bytes)
Definition: big_code.cpp:124