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/*
* Comb4P hash combiner
* (C) 2010 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/comb4p.h>
#include <stdexcept>
namespace Botan {
namespace {
void comb4p_round(secure_vector<byte>& out,
const secure_vector<byte>& in,
byte round_no,
HashFunction& h1,
HashFunction& h2)
{
h1.update(round_no);
h2.update(round_no);
h1.update(in.data(), in.size());
h2.update(in.data(), in.size());
secure_vector<byte> h_buf = h1.final();
xor_buf(out.data(), h_buf.data(), std::min(out.size(), h_buf.size()));
h_buf = h2.final();
xor_buf(out.data(), h_buf.data(), std::min(out.size(), h_buf.size()));
}
}
Comb4P* Comb4P::make(const Spec& spec)
{
if(spec.arg_count() == 2)
{
std::unique_ptr<HashFunction> h1(HashFunction::create(spec.arg(0)));
std::unique_ptr<HashFunction> h2(HashFunction::create(spec.arg(1)));
if(h1 && h2)
return new Comb4P(h1.release(), h2.release());
}
return nullptr;
}
Comb4P::Comb4P(HashFunction* h1, HashFunction* h2) :
m_hash1(h1), m_hash2(h2)
{
if(m_hash1->name() == m_hash2->name())
throw std::invalid_argument("Comb4P: Must use two distinct hashes");
if(m_hash1->output_length() != m_hash2->output_length())
throw std::invalid_argument("Comb4P: Incompatible hashes " +
m_hash1->name() + " and " +
m_hash2->name());
clear();
}
size_t Comb4P::hash_block_size() const
{
if(m_hash1->hash_block_size() == m_hash2->hash_block_size())
return m_hash1->hash_block_size();
/*
* Return LCM of the block sizes? This would probably be OK for
* HMAC, which is the main thing relying on knowing the block size.
*/
return 0;
}
void Comb4P::clear()
{
m_hash1->clear();
m_hash2->clear();
// Prep for processing next message, if any
m_hash1->update(0);
m_hash2->update(0);
}
void Comb4P::add_data(const byte input[], size_t length)
{
m_hash1->update(input, length);
m_hash2->update(input, length);
}
void Comb4P::final_result(byte out[])
{
secure_vector<byte> h1 = m_hash1->final();
secure_vector<byte> h2 = m_hash2->final();
// First round
xor_buf(h1.data(), h2.data(), std::min(h1.size(), h2.size()));
// Second round
comb4p_round(h2, h1, 1, *m_hash1, *m_hash2);
// Third round
comb4p_round(h1, h2, 2, *m_hash1, *m_hash2);
copy_mem(out , h1.data(), h1.size());
copy_mem(out + h1.size(), h2.data(), h2.size());
// Prep for processing next message, if any
m_hash1->update(0);
m_hash2->update(0);
}
}
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