#include <elgamal.h>

Inheritance diagram for Botan::ElGamal_Encryption_Operation:

Public Member Functions
	ElGamal_Encryption_Operation (const ElGamal_PublicKey &key)
SecureVector< byte >	encrypt (const byte msg[], size_t msg_len, RandomNumberGenerator &rng)
size_t	max_input_bits () const

Detailed Description

ElGamal encryption operation

Definition at line 61 of file elgamal.h.

Constructor & Destructor Documentation

◆ ElGamal_Encryption_Operation()

Botan::ElGamal_Encryption_Operation::ElGamal_Encryption_Operation ( const ElGamal_PublicKey & key )

Definition at line 70 of file elgamal.cpp.

   {
   const BigInt& p = key.group_p();
 
   powermod_g_p = Fixed_Base_Power_Mod(key.group_g(), p);
   powermod_y_p = Fixed_Base_Power_Mod(key.get_y(), p);
   mod_p = Modular_Reducer(p);
   }

References Botan::Fixed_Base_Power_Mod::Fixed_Base_Power_Mod(), Botan::DL_Scheme_PublicKey::get_y(), Botan::DL_Scheme_PublicKey::group_g(), Botan::DL_Scheme_PublicKey::group_p(), and Botan::Modular_Reducer::Modular_Reducer().

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

Member Function Documentation

◆ encrypt()

SecureVector< byte > Botan::ElGamal_Encryption_Operation::encrypt	(	const byte	msg[],
		size_t	msg_len,
		RandomNumberGenerator &	rng )

virtual

Implements Botan::PK_Ops::Encryption.

Definition at line 80 of file elgamal.cpp.

   {
   const BigInt& p = mod_p.get_modulus();
 
   BigInt m(msg, msg_len);
 
   if(m >= p)
      throw Invalid_Argument("ElGamal encryption: Input is too large");
 
   BigInt k(rng, 2 * dl_work_factor(p.bits()));
 
   BigInt a = powermod_g_p(k);
   BigInt b = mod_p.multiply(m, powermod_y_p(k));
 
   SecureVector<byte> output(2*p.bytes());
   a.binary_encode(&output[p.bytes() - a.bytes()]);
   b.binary_encode(&output[output.size() / 2 + (p.bytes() - b.bytes())]);
   return output;
   }

References Botan::BigInt::binary_encode(), Botan::BigInt::bits(), Botan::BigInt::bytes(), Botan::dl_work_factor(), and Botan::MemoryRegion< T >::size().

◆ max_input_bits()

size_t Botan::ElGamal_Encryption_Operation::max_input_bits ( ) const

inlinevirtual

Implements Botan::PK_Ops::Encryption.

Definition at line 64 of file elgamal.h.

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

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