aboutsummaryrefslogtreecommitdiffstats
path: root/src/math/numbertheory/pow_mod.h
blob: 1a60ca05fc49d1a781c26d366e2e62795747ede9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
/*
* Modular Exponentiator
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/

#ifndef BOTAN_POWER_MOD_H__
#define BOTAN_POWER_MOD_H__

#include <botan/bigint.h>

namespace Botan {

/**
* Modular Exponentiator Interface
*/
class BOTAN_DLL Modular_Exponentiator
   {
   public:
      virtual void set_base(const BigInt&) = 0;
      virtual void set_exponent(const BigInt&) = 0;
      virtual BigInt execute() const = 0;
      virtual Modular_Exponentiator* copy() const = 0;
      virtual ~Modular_Exponentiator() {}
   };

/**
* Modular Exponentiator Proxy
*/
class BOTAN_DLL Power_Mod
   {
   public:

      enum Usage_Hints {
         NO_HINTS        = 0x0000,

         BASE_IS_FIXED   = 0x0001,
         BASE_IS_SMALL   = 0x0002,
         BASE_IS_LARGE   = 0x0004,
         BASE_IS_2       = 0x0008,

         EXP_IS_FIXED    = 0x0100,
         EXP_IS_SMALL    = 0x0200,
         EXP_IS_LARGE    = 0x0400
      };

      /*
      * Try to choose a good window size
      */
      static u32bit window_bits(u32bit exp_bits, u32bit base_bits,
                                Power_Mod::Usage_Hints hints);

      void set_modulus(const BigInt&, Usage_Hints = NO_HINTS) const;
      void set_base(const BigInt&) const;
      void set_exponent(const BigInt&) const;

      BigInt execute() const;

      Power_Mod& operator=(const Power_Mod&);

      Power_Mod(const BigInt& = 0, Usage_Hints = NO_HINTS);
      Power_Mod(const Power_Mod&);
      ~Power_Mod();
   private:
      mutable Modular_Exponentiator* core;
      Usage_Hints hints;
   };

/**
* Fixed Exponent Modular Exponentiator Proxy
*/
class BOTAN_DLL Fixed_Exponent_Power_Mod : public Power_Mod
   {
   public:
      BigInt operator()(const BigInt& b) const
         { set_base(b); return execute(); }

      Fixed_Exponent_Power_Mod() {}
      Fixed_Exponent_Power_Mod(const BigInt&, const BigInt&,
                               Usage_Hints = NO_HINTS);
   };

/**
* Fixed Base Modular Exponentiator Proxy
*/
class BOTAN_DLL Fixed_Base_Power_Mod : public Power_Mod
   {
   public:
      BigInt operator()(const BigInt& e) const
         { set_exponent(e); return execute(); }

      Fixed_Base_Power_Mod() {}
      Fixed_Base_Power_Mod(const BigInt&, const BigInt&,
                           Usage_Hints = NO_HINTS);
   };

}

#endif