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/**
* (C) 2014 cryptosource GmbH
* (C) 2014 Falko Strenzke fstrenzke@cryptosource.de
*
* Distributed under the terms of the Botan license
*
*/
#include <botan/mce_kem.h>
#include <botan/sha2_64.h>
namespace Botan {
McEliece_KEM_Encryptor::McEliece_KEM_Encryptor(const McEliece_PublicKey& public_key) :
m_raw_pub_op(public_key, public_key.get_code_length())
{
}
std::pair<secure_vector<byte>, secure_vector<byte>>
McEliece_KEM_Encryptor::encrypt(RandomNumberGenerator& rng)
{
const McEliece_PublicKey& key = m_raw_pub_op.get_key();
secure_vector<Botan::byte> plaintext((key.get_message_word_bit_length()+7)/8);
rng.randomize(&plaintext[0], plaintext.size() );
// unset unused bits in the last plaintext byte
u32bit used = key.get_message_word_bit_length() % 8;
if(used)
{
byte mask = (1 << used) - 1;
plaintext[plaintext.size() - 1] &= mask;
}
secure_vector<gf2m> err_pos = create_random_error_positions(key.get_code_length(), key.get_t(), rng);
mceliece_message_parts parts(err_pos, plaintext, key.get_code_length());
secure_vector<Botan::byte> message_and_error_input = parts.get_concat();
SHA_512 hash;
hash.update(message_and_error_input);
secure_vector<byte> sym_key = hash.final();
secure_vector<byte> ciphertext = m_raw_pub_op.encrypt(&message_and_error_input[0],
message_and_error_input.size(), rng);
return std::make_pair(ciphertext, sym_key);
}
McEliece_KEM_Decryptor::McEliece_KEM_Decryptor(const McEliece_PrivateKey& mce_key) :
m_raw_priv_op(mce_key)
{
}
secure_vector<Botan::byte> McEliece_KEM_Decryptor::decrypt(const byte msg[], size_t msg_len)
{
secure_vector<Botan::byte> message_and_error = m_raw_priv_op.decrypt(&msg[0], msg_len );
SHA_512 hash;
hash.update(message_and_error);
secure_vector<byte> sym_key = hash.final();
return sym_key;
}
}
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