RC5.c -- Reference implementation of RC5-32/12/16 in C for Decrypt CO3 Packets

RC5.c

/*
 *   RC5REF.C -- Reference implementation of RC5-32/12/16 in C.
 *   Copyright (C) 1995 RSA Data Security, Inc.
 *   reWritten By Shady Khalifa @shekohex 2018
 *   see this pdf for more info about RC5: https://goo.gl/U5G44K
 */

#include <stdio.h>
#include <stdlib.h>
typedef unsigned int WORD;              // Should be 32-bit = 4 bytes

#define w 32                            // word size in bits
#define r 12                            // number of rounds
#define b 16                            // number of bytes in key
#define c 04                            // number words in key = ceil(8*b/w)
#define t 26                            // size of table S = 2*(r+l) words

WORD S[t];                              // expanded key table
WORD P = 0xB7E15163, Q = 0x9E3779B9;    // magic constants

// Rotation operators, x must be unsigned, to get logical right shift
#define ROTL(x, y) (((x) << (y & (w - 1))) | ((x) >> (w - (y & (w - 1))))) // Rotate Left
#define ROTR(x, y) (((x) >> (y & (w - 1))) | ((x) << (w - (y & (w - 1))))) // Rotate Right


// 2 WORD input pt (plain text) / output ct (encrypted text)
void RC5_Encrypt(WORD *pt, WORD *ct) {
    WORD i,
    A = pt[0] + S[0],
    B = pt[1] + S[1];
    for (i = 1; i <= r; i++) {
        A = ROTL(A ^ B, B) + S[2 * i + 0];
        B = ROTL(B ^ A, A) + S[2 * i + 1];
    }
    ct[0] = A, ct[1] = B;
}

// 2 WORD input ct (encrypted text) / output pt (plain text)
void RC5_Decrypt(WORD *ct, WORD *pt) {
    WORD i,
    A = ct[0],
    B = ct[1];
    for (i = r; i > 0; i--) {
        B = ROTR(B - S[2 * i + 1], A) ^ A;
        A = ROTR(A - S[2 * i + 0], B) ^ B;
    }
    pt[0] = A - S[0], pt[1] = B - S[1];
}

// secret input key K[0...b-1] 
void RC5_Setup(unsigned char *K) {
    WORD i, j, k, A, B,
    u = w / 8, L[c]; 
    // Initialize L, then S, then mix key into S
    for (i = b - 1, L[c - 1] = 0; i != -1; i--) {
        L[i / u] = (L[i / u] << 8) + K[i];
    }
    for (S[0] = P, i=1; i < t; i++) S[i] = S[i - 1] + Q; 
    // 3 * t > 3 * c 
    for (A = B = i = j = k = 0; k < 3 * t; k++) {
        A = S[i] = ROTL(S[i] + (A + B), 0000003);
        B = L[j] = ROTL(L[j] + (A + B), (A + B)); 
        i = (i + 1) % t;
        j = (j + 1) % c;
    }
}

void main() {
     WORD i, j;
     // Is that key is correct?
     //Seed: 0x54 0x54 0x54 0x54
     unsigned char key[b] = { 
        0x8B, 0x10, 0x2F, 0x3A,
        0x93, 0x0D, 0x39, 0x57,
        0xC9, 0x02, 0xDB, 0x37,
        0x1B, 0x74, 0x90, 0x36 };

    //Seed: 0x00 0x00 0x00 0x00
    unsigned char key_old[b] = { 
        0x26, 0x27, 0xF6, 0x85,
        0x97, 0x15, 0xAD, 0x1D,
        0xD2, 0x94, 0xDD, 0xC4,
        0x76, 0x19, 0x39, 0x31 };

     if (sizeof(WORD) != 4) {
        printf("RC5 error: WORD has %d bytes, it should be 4 bytes.\n", sizeof(WORD));
        exit(1);
     }

    // Encrypted Packet [body], without Headers e.g the length, and also with out the seed.
    // Packet Id: 1542
    // Total Lenght 312
    // Seed: 4 bytes
    // Header: 4 Bytes
    WORD ct[304] = {
        0x91, 0x72, 0x8D, 0x2D, 0x9A, 0xFD, 0x86, 0xEA, 0x25, 0xF0, 0x3C,
        0xF2, 0xED, 0xEC, 0x22, 0x81, 0x40, 0xC7, 0x35, 0x85, 0x40, 0x40,
        0x52, 0xC3, 0x09, 0x57, 0x1A, 0xBF, 0xD7, 0x4E, 0xB7, 0xD1, 0x33,
        0xC2, 0x39, 0x58, 0xF9, 0x73, 0x10, 0xF2, 0x3E, 0xBB, 0x19, 0xDD,
        0x30, 0xA6, 0x38, 0x5E, 0x35, 0xF4, 0xF3, 0xFF, 0x7B, 0x27, 0x61,
        0x0C, 0xDF, 0x41, 0x43, 0xDA, 0xC5, 0x15, 0x32, 0x37, 0xB6, 0x5F,
        0x7A, 0xAA, 0xBB, 0xDF, 0x27, 0x4F, 0x0A, 0x7B, 0xE1, 0x90, 0xC2,
        0xED, 0x02, 0x4A, 0xCB, 0xE9, 0xB6, 0x39, 0xF9, 0x73, 0x10, 0xF2,
        0x3E, 0xBB, 0x19, 0xDD, 0x30, 0xA6, 0x38, 0x5E, 0xF9, 0x73, 0x10,
        0xF2, 0x3E, 0xBB, 0x19, 0xDD, 0x30, 0xA6, 0x38, 0x5E, 0xC0, 0xB3,
        0x0E, 0x8A, 0x5B, 0xD6, 0xEE, 0xBB, 0x9A, 0xE7, 0x9B, 0x56, 0xAF,
        0x77, 0x64, 0x01, 0x72, 0xC9, 0xEE, 0x8D, 0x14, 0xBF, 0x2B, 0x44,
        0x92, 0x1B, 0x31, 0xC6, 0xBD, 0xA1, 0x46, 0x39, 0xB2, 0xBE, 0xE2,
        0x6C, 0x50, 0xA4, 0xAA, 0x7A, 0xA6, 0x6D, 0x30, 0xCA, 0x24, 0xF5,
        0xB1, 0xD1, 0xDE, 0x60, 0x91, 0x83, 0xC6, 0x51, 0xC6, 0x04, 0x29,
        0xE3, 0x6B, 0x17, 0x45, 0xD2, 0x0E, 0xDA, 0xB5, 0x38, 0x63, 0x49,
        0x9D, 0xA1, 0xC5, 0xD4, 0x76, 0x5E, 0x49, 0xC1, 0x74, 0x45, 0x4D,
        0x4D, 0x69, 0xE5, 0x75, 0xFD, 0xA9, 0xF5, 0xA7, 0x6E, 0x4D, 0xC7,
        0xF3, 0xBD, 0xBD, 0xF6, 0x8C, 0x4C, 0x54, 0x3D, 0x65, 0x26, 0x80,
        0x2A, 0x13, 0x49, 0x07, 0xEE, 0x00, 0x3D, 0x4C, 0xB9, 0xFC, 0xFB,
        0xCE, 0x55, 0x9E, 0x37, 0xF6, 0xC4, 0xC9, 0x26, 0xF9, 0x73, 0x10,
        0xF2, 0x3E, 0xBB, 0x19, 0xDD, 0x30, 0xA6, 0x38, 0x5E, 0xD4, 0x18,
        0x0E, 0x7F, 0x58, 0xFE, 0xBF, 0x8D, 0x95, 0x45, 0xB5, 0x66, 0xCA,
        0x62, 0x36, 0xA6, 0x09, 0x6A, 0xBC, 0xF5, 0xBD, 0x02, 0x08, 0x5E,
        0x67, 0x95, 0x4C, 0xCB, 0xBC, 0x08, 0x6B, 0x8C, 0xA6, 0xDA, 0x12,
        0xB2, 0x75, 0xE5, 0x27, 0xF3, 0x05, 0x32, 0x59, 0xEC, 0xAA, 0x20,
        0x8C, 0x3D, 0x58, 0x90, 0x87, 0x46, 0x43, 0xF0, 0xB5, 0x75, 0xFE,
        0x46, 0x10, 0x9D, 0xF4, 0x1E, 0x32, 0x2D,                       };
    // TODO: Read the row packet form a file !

    // Setupt the RC5 Table from that key, then print it *the key*
    RC5_Setup(key);
    printf(" key = ");
    for (j = 0; j < b; j++) printf("%.2X ", key[j]); // As Hex

    int ct_len = sizeof(ct) / sizeof(WORD);
    // The Decrypted Pakcet Body
    WORD pt[ct_len];
    int n = ct_len / 2;

    for (i = 0; i < n; i++) {
        int index = i * 2;
        WORD ct_slice[2], pt_slice[2] = { 0x00, 0x00 };
        ct_slice[0] = ct[index];
        ct_slice[1] = ct[index + 1];

        RC5_Decrypt(ct_slice, pt_slice);

        pt[index] = pt_slice[0];
        pt[index + 1] = pt_slice[1];
        printf("\n#%.3d PlainText(%.3d, %.3d): %.8X %.8X\t", index, index, index + 1, pt[index], pt[index + 1]);
        printf(" CipherText(%.3d, %.3d): %.8X %.8X\n", index, index + 1, ct[index], ct[index + 1]);
    }

    int written = 0;
    FILE *f = fopen("packet.data", "wb");
    written = fwrite(pt, sizeof(WORD), sizeof(pt), f);

    if (written == 0) {
        printf("Error during writing to file !");
        exit(1);
    }
    fclose(f);
    exit(0);
}

It's still buggy, but it mostly not works as intended to be
of course the implementation itself of RC5 is working as supposed to be, you can test it , but we think the key is wrong.

so any ideas ?