_keccak_function.c

#include <stdint.h>
#include <string.h>

#define ROUNDS 24
#define STATE_SIZE 5

// Rotation constants
const unsigned int rotation_offsets[5][5] = {
    {0, 36, 3, 41, 18},
    {1, 44, 10, 45, 2},
    {62, 6, 43, 15, 61},
    {28, 55, 25, 21, 56},
    {27, 20, 39, 8, 14}
};

// Round constants
const uint64_t round_constants[ROUNDS] = {
    0x0000000000000001, 0x0000000000008082, 0x800000000000808a,
    0x8000000080008000, 0x000000000000808b, 0x0000000080000001,
    0x8000000080008081, 0x8000000000008009, 0x000000000000008a,
    0x0000000000000088, 0x0000000080008009, 0x000000008000000a,
    0x000000008000808b, 0x800000000000008b, 0x8000000000008089,
    0x8000000000008003, 0x8000000000008002, 0x8000000000000080,
    0x000000000000800a, 0x800000008000000a, 0x8000000080008081,
    0x8000000000008080, 0x0000000080000001, 0x8000000080008008
};

// Utility functions
uint64_t rotate_left(uint64_t word, int offset) {
    return (word << offset) | (word >> (64 - offset));
}

void keccak_theta(uint64_t state[STATE_SIZE][STATE_SIZE]) {
    // Example theta implementation
}

void keccak_rho_pi(uint64_t state[STATE_SIZE][STATE_SIZE]) {
    // Example rho and pi implementation
}

void keccak_chi(uint64_t state[STATE_SIZE][STATE_SIZE]) {
    // Example chi implementation
}

void keccak_iota(uint64_t state[STATE_SIZE][STATE_SIZE], int round_index) {
    // Example iota implementation
}

void keccak_permute(uint64_t state[STATE_SIZE][STATE_SIZE]) {
    for (int round = 0; round < ROUNDS; round++) {
        keccak_theta(state);
        keccak_rho_pi(state);
        keccak_chi(state);
        keccak_iota(state, round);
    }
}

void keccak_absorb(uint64_t state[STATE_SIZE][STATE_SIZE], const uint8_t *input, size_t input_len) {
    // Absorption logic
}

void keccak_squeeze(uint64_t state[STATE_SIZE][STATE_SIZE], uint8_t *output, size_t output_len) {
    // Squeezing logic
}

void keccak(const uint8_t *input, size_t input_len, uint8_t *output, size_t output_len) {
    uint64_t state[STATE_SIZE][STATE_SIZE] = {0};
    keccak_absorb(state, input, input_len);
    keccak_permute(state);
    keccak_squeeze(state, output, output_len);
}