1 files changed, 155 insertions, 0 deletions
diff --git a/src/bigint/pow_mod.cpp b/src/bigint/pow_mod.cpp
new file mode 100644
index 000000000..17ca7b796
--- /dev/null
+++ b/src/bigint/pow_mod.cpp
@@ -0,0 +1,155 @@
+/*************************************************
+* Modular Exponentiation Proxy Source File       *
+* (C) 1999-2007 Jack Lloyd                       *
+*************************************************/
+
+#include <botan/pow_mod.h>
+#include <botan/engine.h>
+
+namespace Botan {
+
+/*************************************************
+* Power_Mod Constructor                          *
+*************************************************/
+Power_Mod::Power_Mod(const BigInt& n, Usage_Hints hints)
+   {
+   core = 0;
+   set_modulus(n, hints);
+   }
+
+/*************************************************
+* Power_Mod Copy Constructor                     *
+*************************************************/
+Power_Mod::Power_Mod(const Power_Mod& other)
+   {
+   core = 0;
+   if(other.core)
+      core = other.core->copy();
+   }
+
+/*************************************************
+* Power_Mod Assignment Operator                  *
+*************************************************/
+Power_Mod& Power_Mod::operator=(const Power_Mod& other)
+   {
+   delete core;
+   core = 0;
+   if(other.core)
+      core = other.core->copy();
+   return (*this);
+   }
+
+/*************************************************
+* Power_Mod Destructor                           *
+*************************************************/
+Power_Mod::~Power_Mod()
+   {
+   delete core;
+   }
+
+/*************************************************
+* Set the modulus                                *
+*************************************************/
+void Power_Mod::set_modulus(const BigInt& n, Usage_Hints hints) const
+   {
+   delete core;
+   core = ((n == 0) ? 0 : Engine_Core::mod_exp(n, hints));
+   }
+
+/*************************************************
+* Set the base                                   *
+*************************************************/
+void Power_Mod::set_base(const BigInt& b) const
+   {
+   if(b.is_zero() || b.is_negative())
+      throw Invalid_Argument("Power_Mod::set_base: arg must be > 0");
+
+   if(!core)
+      throw Internal_Error("Power_Mod::set_base: core was NULL");
+   core->set_base(b);
+   }
+
+/*************************************************
+* Set the exponent                               *
+*************************************************/
+void Power_Mod::set_exponent(const BigInt& e) const
+   {
+   if(e.is_negative())
+      throw Invalid_Argument("Power_Mod::set_exponent: arg must be > 0");
+
+   if(!core)
+      throw Internal_Error("Power_Mod::set_exponent: core was NULL");
+   core->set_exponent(e);
+   }
+
+/*************************************************
+* Compute the result                             *
+*************************************************/
+BigInt Power_Mod::execute() const
+   {
+   if(!core)
+      throw Internal_Error("Power_Mod::execute: core was NULL");
+   return core->execute();
+   }
+
+namespace {
+
+/*************************************************
+* Choose potentially useful hints                *
+*************************************************/
+Power_Mod::Usage_Hints choose_base_hints(const BigInt& b, const BigInt& n)
+   {
+   if(b == 2)
+      return Power_Mod::Usage_Hints(Power_Mod::BASE_IS_2 |
+                                    Power_Mod::BASE_IS_SMALL);
+
+   const u32bit b_bits = b.bits();
+   const u32bit n_bits = n.bits();
+
+   if(b_bits < n_bits / 32)
+      return Power_Mod::BASE_IS_SMALL;
+   if(b_bits > n_bits / 4)
+      return Power_Mod::BASE_IS_LARGE;
+
+   return Power_Mod::NO_HINTS;
+   }
+
+/*************************************************
+* Choose potentially useful hints                *
+*************************************************/
+Power_Mod::Usage_Hints choose_exp_hints(const BigInt& e, const BigInt& n)
+   {
+   const u32bit e_bits = e.bits();
+   const u32bit n_bits = n.bits();
+
+   if(e_bits < n_bits / 32)
+      return Power_Mod::BASE_IS_SMALL;
+   if(e_bits > n_bits / 4)
+      return Power_Mod::BASE_IS_LARGE;
+   return Power_Mod::NO_HINTS;
+   }
+
+}
+
+/*************************************************
+* Fixed_Exponent_Power_Mod Constructor           *
+*************************************************/
+Fixed_Exponent_Power_Mod::Fixed_Exponent_Power_Mod(const BigInt& e,
+                                                   const BigInt& n,
+                                                   Usage_Hints hints) :
+   Power_Mod(n, Usage_Hints(hints | EXP_IS_FIXED | choose_exp_hints(e, n)))
+   {
+   set_exponent(e);
+   }
+
+/*************************************************
+* Fixed_Base_Power_Mod Constructor               *
+*************************************************/
+Fixed_Base_Power_Mod::Fixed_Base_Power_Mod(const BigInt& b, const BigInt& n,
+                                           Usage_Hints hints) :
+   Power_Mod(n, Usage_Hints(hints | BASE_IS_FIXED | choose_base_hints(b, n)))
+   {
+   set_base(b);
+   }
+
+}