Botan  2.15.0
Crypto and TLS for C++11
pow_mod.h
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1 /*
2 * Modular Exponentiator
3 * (C) 1999-2007 Jack Lloyd
4 *
5 * Botan is released under the Simplified BSD License (see license.txt)
6 */
7 
8 #ifndef BOTAN_POWER_MOD_H_
9 #define BOTAN_POWER_MOD_H_
10 
11 #include <botan/bigint.h>
12 
14 
15 namespace Botan {
16 
17 class Modular_Exponentiator;
18 
19 /**
20 * Modular Exponentiator Proxy
21 */
23  {
24  public:
25 
26  enum Usage_Hints {
27  NO_HINTS = 0x0000,
28 
29  BASE_IS_FIXED = 0x0001,
30  BASE_IS_SMALL = 0x0002,
31  BASE_IS_LARGE = 0x0004,
32  BASE_IS_2 = 0x0008,
33 
34  EXP_IS_FIXED = 0x0100,
35  EXP_IS_SMALL = 0x0200,
36  EXP_IS_LARGE = 0x0400
37  };
38 
39  /*
40  * Try to choose a good window size
41  */
42  static size_t window_bits(size_t exp_bits, size_t base_bits,
44 
45  /**
46  * @param modulus the modulus
47  * @param hints Passed to set_modulus if modulus > 0
48  * @param disable_montgomery_arith Disables use of Montgomery
49  * representation. Likely only useful for testing.
50  */
51  void set_modulus(const BigInt& modulus,
52  Usage_Hints hints = NO_HINTS,
53  bool disable_montgomery_arith = false) const;
54 
55  /**
56  * Set the base
57  */
58  void set_base(const BigInt& base) const;
59 
60  /**
61  * Set the exponent
62  */
63  void set_exponent(const BigInt& exponent) const;
64 
65  /**
66  * All three of the above functions must have already been called.
67  * @return result of g^x%p
68  */
69  BigInt execute() const;
70 
71  Power_Mod& operator=(const Power_Mod&);
72 
73  /**
74  * @param modulus Optionally call set_modulus
75  * @param hints Passed to set_modulus if modulus > 0
76  * @param disable_montgomery_arith Disables use of Montgomery
77  * representation. Likely only useful for testing.
78  */
79  Power_Mod(const BigInt& modulus = 0,
80  Usage_Hints hints = NO_HINTS,
81  bool disable_montgomery_arith = false);
82  Power_Mod(const Power_Mod&);
83  virtual ~Power_Mod();
84  private:
85  mutable std::unique_ptr<Modular_Exponentiator> m_core;
86  };
87 
88 /**
89 * Fixed Exponent Modular Exponentiator Proxy
90 */
92  {
93  public:
94  BigInt operator()(const BigInt& b) const
95  { set_base(b); return execute(); }
96 
97  Fixed_Exponent_Power_Mod() = default;
98 
99  Fixed_Exponent_Power_Mod(const BigInt& exponent,
100  const BigInt& modulus,
101  Usage_Hints hints = NO_HINTS);
102  };
103 
104 /**
105 * Fixed Base Modular Exponentiator Proxy
106 */
108  {
109  public:
110  BigInt operator()(const BigInt& e) const
111  { set_exponent(e); return execute(); }
112 
113  Fixed_Base_Power_Mod() = default;
114 
115  Fixed_Base_Power_Mod(const BigInt& base,
116  const BigInt& modulus,
117  Usage_Hints hints = NO_HINTS);
118  };
119 
120 }
121 
122 #endif
int(* final)(unsigned char *, CTX *)
#define BOTAN_PUBLIC_API(maj, min)
Definition: compiler.h:31
BigInt operator()(const BigInt &b) const
Definition: pow_mod.h:94
void set_exponent(const BigInt &exponent) const
Definition: pow_mod.cpp:211
BigInt const BigInt & modulus
Definition: numthry.h:100
Definition: alg_id.cpp:13
BigInt execute() const
Definition: pow_mod.cpp:224
void set_base(const BigInt &base) const
Definition: pow_mod.cpp:198
BigInt operator()(const BigInt &e) const
Definition: pow_mod.h:110
#define BOTAN_FUTURE_INTERNAL_HEADER(hdr)
Definition: compiler.h:145