// ©AngelaMos | 2026
// crypto_tool.c

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

static const uint32_t K[] = {
    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
    0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
    0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
    0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
    0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
    0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
    0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
    0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
    0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
};

static uint32_t rotr(uint32_t x, int n) {
    return (x >> n) | (x << (32 - n));
}

static void sha256_transform(uint32_t state[8], const uint8_t block[64]) {
    uint32_t w[64];
    for (int i = 0; i < 16; i++) {
        w[i] = ((uint32_t)block[i*4] << 24) |
               ((uint32_t)block[i*4+1] << 16) |
               ((uint32_t)block[i*4+2] << 8) |
               ((uint32_t)block[i*4+3]);
    }
    for (int i = 16; i < 64; i++) {
        uint32_t s0 = rotr(w[i-15], 7) ^ rotr(w[i-15], 18) ^ (w[i-15] >> 3);
        uint32_t s1 = rotr(w[i-2], 17) ^ rotr(w[i-2], 19) ^ (w[i-2] >> 10);
        w[i] = w[i-16] + s0 + w[i-7] + s1;
    }

    uint32_t a = state[0], b = state[1], c = state[2], d = state[3];
    uint32_t e = state[4], f = state[5], g = state[6], h = state[7];

    for (int i = 0; i < 64; i++) {
        uint32_t S1 = rotr(e, 6) ^ rotr(e, 11) ^ rotr(e, 25);
        uint32_t ch = (e & f) ^ (~e & g);
        uint32_t t1 = h + S1 + ch + K[i] + w[i];
        uint32_t S0 = rotr(a, 2) ^ rotr(a, 13) ^ rotr(a, 22);
        uint32_t maj = (a & b) ^ (a & c) ^ (b & c);
        uint32_t t2 = S0 + maj;

        h = g; g = f; f = e; e = d + t1;
        d = c; c = b; b = a; a = t1 + t2;
    }

    state[0] += a; state[1] += b; state[2] += c; state[3] += d;
    state[4] += e; state[5] += f; state[6] += g; state[7] += h;
}

static void sha256(const uint8_t *data, size_t len, uint8_t hash[32]) {
    uint32_t state[8] = {
        0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
        0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19,
    };

    uint8_t block[64];
    size_t i;
    for (i = 0; i + 64 <= len; i += 64) {
        sha256_transform(state, data + i);
    }

    size_t rem = len - i;
    memset(block, 0, 64);
    memcpy(block, data + i, rem);
    block[rem] = 0x80;

    if (rem >= 56) {
        sha256_transform(state, block);
        memset(block, 0, 64);
    }

    uint64_t bits = (uint64_t)len * 8;
    for (int j = 0; j < 8; j++) {
        block[63 - j] = (uint8_t)(bits >> (j * 8));
    }
    sha256_transform(state, block);

    for (int j = 0; j < 8; j++) {
        hash[j*4]   = (uint8_t)(state[j] >> 24);
        hash[j*4+1] = (uint8_t)(state[j] >> 16);
        hash[j*4+2] = (uint8_t)(state[j] >> 8);
        hash[j*4+3] = (uint8_t)(state[j]);
    }
}

static void xor_encrypt(uint8_t *data, size_t len, const uint8_t *key, size_t klen) {
    for (size_t i = 0; i < len; i++) {
        data[i] ^= key[i % klen];
    }
}

int main(int argc, char *argv[]) {
    if (argc < 2) {
        fprintf(stderr, "Usage: %s <file>\n", argv[0]);
        return 1;
    }

    FILE *fp = fopen(argv[1], "rb");
    if (!fp) {
        perror("fopen");
        return 1;
    }

    fseek(fp, 0, SEEK_END);
    long fsize = ftell(fp);
    rewind(fp);

    uint8_t *buf = malloc(fsize);
    if (!buf) {
        fclose(fp);
        return 1;
    }
    fread(buf, 1, fsize, fp);
    fclose(fp);

    uint8_t hash[32];
    sha256(buf, fsize, hash);

    printf("SHA-256: ");
    for (int i = 0; i < 32; i++) {
        printf("%02x", hash[i]);
    }
    printf("\n");

    uint8_t key[] = {0xDE, 0xAD, 0xBE, 0xEF, 0xCA, 0xFE, 0xBA, 0xBE};
    xor_encrypt(buf, fsize, key, sizeof(key));
    printf("XOR-encrypted %ld bytes with 8-byte key.\n", fsize);

    uint8_t enc_hash[32];
    sha256(buf, fsize, enc_hash);
    printf("ENC-256: ");
    for (int i = 0; i < 32; i++) {
        printf("%02x", enc_hash[i]);
    }
    printf("\n");

    free(buf);
    return 0;
}