integrity.c

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

// Convert bytes to hex string
void to_hex(const unsigned char *hash, int len, char *output) {
    for (int i = 0; i < len; i++)
        sprintf(output + (i * 2), "%02x", hash[i]);
    output[len * 2] = '\0';
}

/* ------------------------------------
 * LEVEL 3: Key-Mixed Rolling Hash
 * ------------------------------------
 * - Uses key as dynamic modifier
 * - Adds feedback and modular arithmetic
 * - Stronger custom design
 */
void key_mixed_rolling_hash(const char *data, int datalen, const char *key, unsigned char *hash, int hash_len) {
    int keylen = strlen(key);

    uint64_t acc = 0x123456789ABCDEFULL;


    for (int i = 0; i < datalen; i++) {
        unsigned char d = data[i];
        unsigned char k = key[i % keylen];



        acc ^= ((uint64_t)d << (i % 8)) | ((uint64_t)k << ((i + 3) % 8));



        acc = (acc * 1315423911ULL + k * 2654435761ULL) ^ (acc >> 11);
    }

    for (int i = 0; i < hash_len; i++) {
        acc = (acc >> 7) ^ (acc << 3) ^ key[i % keylen];
        hash[i] = (acc ^ (acc >> 16)) & 0xFF;
    }
}