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/*
This code is written by kerukuro and released into public domain.
*/
#ifndef DIGESTPP_PROVIDERS_SHAKE_HPP
#define DIGESTPP_PROVIDERS_SHAKE_HPP
#include "../../detail/functions.hpp"
#include "../../detail/absorb_data.hpp"
#include "sha3_provider.hpp"
#include <array>
namespace digestpp
{
namespace detail
{
namespace shake_functions
{
static inline size_t left_encode(size_t num, unsigned char* buf)
{
// first, calculate length
unsigned char n = 1;
size_t tmp = num;
while (tmp >>= 8)
++n;
buf[0] = n;
size_t result = n + 1;
size_t i = 0;
while (n)
buf[n--] = static_cast<unsigned char>(num >> (8*i++));
return result;
}
static inline size_t right_encode(size_t num, unsigned char* buf, bool k12)
{
// first, calculate length
unsigned char n = k12 ? num ? 1 : 0 : 1;
size_t tmp = num;
while (tmp >>= 8)
++n;
buf[n] = n;
size_t result = n + 1;
size_t i = 0;
while (n--)
buf[n] = static_cast<unsigned char>(num >> (8*i++));
return result;
}
} // namespace shake_functions
template<size_t B, int R>
class shake_provider
{
public:
static const bool is_xof = true;
shake_provider()
{
static_assert(B == 128 || B == 256, "SHAKE only supports 128 and 256 bits");
}
~shake_provider()
{
clear();
}
inline void set_function_name(const std::string& function_name)
{
N = function_name;
}
inline void set_customization(const std::string& customization)
{
S = customization;
}
inline void init()
{
zero_memory(A);
pos = 0;
squeezing = false;
suffix = 0;
if (!N.empty() || !S.empty())
{
unsigned char buf[1024];
size_t r = rate / 8;
size_t len = shake_functions::left_encode(r, buf);
size_t total = len;
update(buf, len);
len = shake_functions::left_encode(N.length() * 8, buf);
total += len;
update(buf, len);
if (!N.empty())
update(reinterpret_cast<const unsigned char*>(N.data()), N.length());
len = shake_functions::left_encode(S.length() * 8, buf);
update(buf, len);
total += len;
if (!S.empty())
update(reinterpret_cast<const unsigned char*>(S.data()), S.length());
total += S.length() + N.length();
len = r - (total % r);
memset(buf, 0, len);
update(buf, len);
}
}
inline void update(const unsigned char* data, size_t len)
{
detail::absorb_bytes(data, len, rate / 8, rate / 8, m.data(), pos, total,
[this](const unsigned char* data, size_t len) { sha3_functions::transform<R>(data, len, A.data(), rate); });
}
inline void set_suffix(unsigned char s)
{
suffix = s;
}
inline void squeeze(unsigned char* hash, size_t hs)
{
size_t r = rate / 8;
size_t processed = 0;
if (!squeezing)
{
m[pos++] = suffix ? suffix : N.empty() && S.empty() ? 0x1F : 0x04;
if (r != pos)
memset(&m[pos], 0, r - pos);
m[r - 1] |= 0x80;
sha3_functions::transform<R>(m.data(), 1, A.data(), rate);
squeezing = true;
}
else if (pos < r)
{
size_t to_copy = std::min(hs, r - pos);
memcpy(hash, reinterpret_cast<unsigned char*>(A.data()) + pos, to_copy);
processed += to_copy;
pos += to_copy;
}
while (processed < hs)
{
if (processed)
sha3_functions::transform<R>(A.data());
pos = std::min(hs - processed, r);
memcpy(hash + processed, A.data(), pos);
processed += pos;
}
}
inline void clear()
{
zero_memory(A);
zero_memory(m);
zero_memory(N);
zero_memory(S);
N.clear();
S.clear();
}
private:
std::array<uint64_t, 25> A;
std::array<unsigned char, 168> m;
std::string N;
std::string S;
const size_t rate = B == 128 ? 1344 : 1088;
size_t pos;
size_t total;
bool squeezing;
unsigned char suffix;
};
} // namespace detail
} // namespace digestpp
#endif // DIGESTPP_PROVIDERS_SHAKE_HPP
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