Botan::ElGamal_Decryption_Operation Class Reference

#include <elgamal.h>

Inheritance diagram for Botan::ElGamal_Decryption_Operation:

Public Member Functions
SecureVector< byte >	decrypt (const byte msg[], size_t msg_len)
	ElGamal_Decryption_Operation (const ElGamal_PrivateKey &key)
size_t	max_input_bits () const

Detailed Description

ElGamal decryption operation

Definition at line 79 of file elgamal.h.

Constructor & Destructor Documentation

ElGamal_Decryption_Operation()

Botan::ElGamal_Decryption_Operation::ElGamal_Decryption_Operation

(

const ElGamal_PrivateKey &

key

)

Definition at line 101 of file elgamal.cpp.

   {
   const BigInt& p = key.group_p();
 
   powermod_x_p = Fixed_Exponent_Power_Mod(key.get_x(), p);
   mod_p = Modular_Reducer(p);
 
   BigInt k(global_state().global_rng(), p.bits() - 1);
   blinder = Blinder(k, powermod_x_p(k), p);
   }

References Botan::BigInt::bits(), Botan::Blinder::Blinder(), Botan::Fixed_Exponent_Power_Mod::Fixed_Exponent_Power_Mod(), Botan::DL_Scheme_PrivateKey::get_x(), Botan::global_state(), Botan::DL_Scheme_PublicKey::group_p(), and Botan::Modular_Reducer::Modular_Reducer().

Referenced by Botan::Core_Engine::get_decryption_op().

Member Function Documentation

decrypt()

SecureVector< byte > Botan::ElGamal_Decryption_Operation::decrypt ( const byte msg[], size_t msg_len )

virtual

Implements Botan::PK_Ops::Decryption.

Definition at line 113 of file elgamal.cpp.

   {
   const BigInt& p = mod_p.get_modulus();
 
   const size_t p_bytes = p.bytes();
 
   if(msg_len != 2 * p_bytes)
      throw Invalid_Argument("ElGamal decryption: Invalid message");
 
   BigInt a(msg, p_bytes);
   BigInt b(msg + p_bytes, p_bytes);
 
   if(a >= p || b >= p)
      throw Invalid_Argument("ElGamal decryption: Invalid message");
 
   a = blinder.blind(a);
 
   BigInt r = mod_p.multiply(b, inverse_mod(powermod_x_p(a), p));
 
   return BigInt::encode(blinder.unblind(r));
   }

References Botan::BigInt::bytes(), Botan::BigInt::encode(), and Botan::inverse_mod().

max_input_bits()

size_t Botan::ElGamal_Decryption_Operation::max_input_bits ( ) const

inlinevirtual

Implements Botan::PK_Ops::Decryption.

Definition at line 82 of file elgamal.h.

{ return mod_p.get_modulus().bits() - 1; }

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The documentation for this class was generated from the following files:

• src/pubkey/elgamal/elgamal.h
• src/pubkey/elgamal/elgamal.cpp