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/*************************************************
* DLIES Source File *
* (C) 1999-2007 The Botan Project *
*************************************************/
#include <botan/dlies.h>
#include <botan/lookup.h>
#include <botan/look_pk.h>
#include <botan/bit_ops.h>
#include <memory>
namespace Botan {
/*************************************************
* DLIES_Encryptor Constructor *
*************************************************/
DLIES_Encryptor::DLIES_Encryptor(const PK_Key_Agreement_Key& k,
const std::string& kdf,
const std::string& mac, u32bit mk_len) :
key(k), kdf_algo(kdf), mac_algo(mac), MAC_KEYLEN(mk_len)
{
}
/*************************************************
* DLIES Encryption *
*************************************************/
SecureVector<byte> DLIES_Encryptor::enc(const byte in[], u32bit length) const
{
if(length > maximum_input_size())
throw Invalid_Argument("DLIES: Plaintext too large");
if(other_key.is_empty())
throw Invalid_State("DLIES: The other key was never set");
std::auto_ptr<KDF> kdf(get_kdf(kdf_algo));
std::auto_ptr<MessageAuthenticationCode> mac(get_mac(mac_algo));
MemoryVector<byte> v = key.public_value();
SecureVector<byte> out(v.size() + length + mac->OUTPUT_LENGTH);
out.copy(v, v.size());
out.copy(v.size(), in, length);
SecureVector<byte> vz(v, key.derive_key(other_key, other_key.size()));
const u32bit K_LENGTH = length + MAC_KEYLEN;
OctetString K = kdf->derive_key(K_LENGTH, vz, vz.size());
if(K.length() != K_LENGTH)
throw Encoding_Error("DLIES: KDF did not provide sufficient output");
byte* C = out + v.size();
xor_buf(C, K.begin() + MAC_KEYLEN, length);
mac->set_key(K.begin(), MAC_KEYLEN);
mac->update(C, length);
for(u32bit j = 0; j != 8; ++j)
mac->update(0);
mac->final(C + length);
return out;
}
/*************************************************
* Set the other parties public key *
*************************************************/
void DLIES_Encryptor::set_other_key(const MemoryRegion<byte>& ok)
{
other_key = ok;
}
/*************************************************
* Return the max size, in bytes, of a message *
*************************************************/
u32bit DLIES_Encryptor::maximum_input_size() const
{
return 32;
}
/*************************************************
* DLIES_Decryptor Constructor *
*************************************************/
DLIES_Decryptor::DLIES_Decryptor(const PK_Key_Agreement_Key& k,
const std::string& kdf,
const std::string& mac, u32bit mk_len) :
key(k), kdf_algo(kdf), mac_algo(mac),
MAC_KEYLEN(mk_len), PUBLIC_LEN(key.public_value().size())
{
}
/*************************************************
* DLIES Decryption *
*************************************************/
SecureVector<byte> DLIES_Decryptor::dec(const byte msg[], u32bit length) const
{
std::auto_ptr<MessageAuthenticationCode> mac(get_mac(mac_algo));
if(length < PUBLIC_LEN + mac->OUTPUT_LENGTH)
throw Decoding_Error("DLIES decryption: ciphertext is too short");
std::auto_ptr<KDF> kdf(get_kdf(kdf_algo));
const u32bit CIPHER_LEN = length - PUBLIC_LEN - mac->OUTPUT_LENGTH;
SecureVector<byte> v(msg, PUBLIC_LEN);
SecureVector<byte> C(msg + PUBLIC_LEN, CIPHER_LEN);
SecureVector<byte> T(msg + PUBLIC_LEN + CIPHER_LEN, mac->OUTPUT_LENGTH);
SecureVector<byte> vz(v, key.derive_key(v, v.size()));
const u32bit K_LENGTH = C.size() + MAC_KEYLEN;
OctetString K = kdf->derive_key(K_LENGTH, vz, vz.size());
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(u32bit j = 0; j != 8; ++j)
mac->update(0);
SecureVector<byte> T2 = mac->final();
if(T != T2)
throw Integrity_Failure("DLIES: message authentication failed");
xor_buf(C, K.begin() + MAC_KEYLEN, C.size());
return C;
}
}
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