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/*
* Base helper class for implementing sponge constructions like Keccak or Ascon
* (C) 2025 Jack Lloyd
* 2025 René Meusel
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#ifndef BOTAN_SPONGE_CONSTRUCTION_H_
#define BOTAN_SPONGE_CONSTRUCTION_H_
#include <botan/assert.h>
#include <botan/types.h>
#include <array>
namespace Botan {
/**
* A generic sponge construction with a fixed state size defined in terms of
* "words" of an unsigned integral type.
*
* This is meant to be used as a base class for specific sponge constructions
* like Keccak or Ascon.
*/
template <size_t words, std::unsigned_integral word = uint64_t>
class Sponge {
public:
using word_t = word;
using state_t = std::array<word, words>;
constexpr static size_t word_bytes = sizeof(word);
constexpr static size_t word_bits = word_bytes * 8;
struct Config final {
size_t bit_rate; /// The number of bits that using algorithms can modify between permutations
state_t initial_state; /// The state of the sponge state at initialization
};
public:
constexpr explicit Sponge(Config config) : m_S(config.initial_state), m_S_cursor(0), m_bit_rate(config.bit_rate) {
BOTAN_ARG_CHECK(m_bit_rate % word_bits == 0 && m_bit_rate < words * word_bits, "Invalid sponge bit rate");
}
constexpr static size_t state_bytes() { return sizeof(state_t); }
constexpr static size_t state_bits() { return state_bytes() * 8; }
constexpr size_t bit_rate() const { return m_bit_rate; }
constexpr size_t byte_rate() const { return m_bit_rate / 8; }
constexpr size_t bit_capacity() const { return state_bits() - bit_rate(); }
constexpr size_t byte_capacity() const { return state_bytes() - byte_rate(); }
constexpr auto& state() { return m_S; }
size_t cursor() const { return m_S_cursor; }
size_t& _cursor() { return m_S_cursor; }
protected:
void reset_cursor() { m_S_cursor = 0; }
private:
state_t m_S;
size_t m_S_cursor;
size_t m_bit_rate;
};
} // namespace Botan
#endif