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/*
* DLIES
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/dlies.h>
#include <botan/internal/xor_buf.h>
namespace Botan {
/*
* DLIES_Encryptor Constructor
*/
DLIES_Encryptor::DLIES_Encryptor(const PK_Key_Agreement_Key& key,
KDF* kdf_obj,
MessageAuthenticationCode* mac_obj,
size_t mac_kl) :
ka(key, "Raw"),
kdf(kdf_obj),
mac(mac_obj),
mac_keylen(mac_kl)
{
my_key = key.public_value();
}
/*
* DLIES Encryption
*/
std::vector<byte> DLIES_Encryptor::enc(const byte in[], size_t length,
RandomNumberGenerator&) const
{
if(length > maximum_input_size())
throw Invalid_Argument("DLIES: Plaintext too large");
if(other_key.empty())
throw Invalid_State("DLIES: The other key was never set");
secure_vector<byte> out(my_key.size() + length + mac->output_length());
buffer_insert(out, 0, my_key);
buffer_insert(out, my_key.size(), in, length);
secure_vector<byte> vz(my_key.begin(), my_key.end());
vz += ka.derive_key(0, other_key).bits_of();
const size_t K_LENGTH = length + mac_keylen;
OctetString K = kdf->derive_key(K_LENGTH, vz);
if(K.length() != K_LENGTH)
throw Encoding_Error("DLIES: KDF did not provide sufficient output");
byte* C = &out[my_key.size()];
xor_buf(C, K.begin() + mac_keylen, length);
mac->set_key(K.begin(), mac_keylen);
mac->update(C, length);
for(size_t j = 0; j != 8; ++j)
mac->update(0);
mac->final(C + length);
return unlock(out);
}
/*
* Set the other parties public key
*/
void DLIES_Encryptor::set_other_key(const std::vector<byte>& ok)
{
other_key = ok;
}
/*
* Return the max size, in bytes, of a message
*/
size_t DLIES_Encryptor::maximum_input_size() const
{
return 32;
}
/*
* DLIES_Decryptor Constructor
*/
DLIES_Decryptor::DLIES_Decryptor(const PK_Key_Agreement_Key& key,
KDF* kdf_obj,
MessageAuthenticationCode* mac_obj,
size_t mac_kl) :
ka(key, "Raw"),
kdf(kdf_obj),
mac(mac_obj),
mac_keylen(mac_kl)
{
my_key = key.public_value();
}
/*
* DLIES Decryption
*/
secure_vector<byte> DLIES_Decryptor::dec(const byte msg[], size_t length) const
{
if(length < my_key.size() + mac->output_length())
throw Decoding_Error("DLIES decryption: ciphertext is too short");
const size_t CIPHER_LEN = length - my_key.size() - mac->output_length();
std::vector<byte> v(msg, msg + my_key.size());
secure_vector<byte> C(msg + my_key.size(), msg + my_key.size() + CIPHER_LEN);
secure_vector<byte> T(msg + my_key.size() + CIPHER_LEN,
msg + my_key.size() + CIPHER_LEN + mac->output_length());
secure_vector<byte> vz(msg, msg + my_key.size());
vz += ka.derive_key(0, v).bits_of();
const size_t K_LENGTH = C.size() + mac_keylen;
OctetString K = kdf->derive_key(K_LENGTH, vz);
if(K.length() != K_LENGTH)
throw Encoding_Error("DLIES: KDF did not provide sufficient output");
mac->set_key(K.begin(), mac_keylen);
mac->update(C);
for(size_t j = 0; j != 8; ++j)
mac->update(0);
secure_vector<byte> T2 = mac->final();
if(T != T2)
throw Decoding_Error("DLIES: message authentication failed");
xor_buf(C, K.begin() + mac_keylen, C.size());
return C;
}
}
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