SBoxinAES.cpp

//This code is contributed by SOurajita Dewasi
#include <iostream>

using namespace std;

const int LENGTH = 16; //byte
const int ROUND = 10;

const unsigned char SBOX[256] = {
    0x63, 0x7C, 0x77, 0x7B, 0xF2, 0x6B, 0x6F, 0xC5, 0x30, 0x01, 0x67, 0x2B, 0xFE, 0xD7, 0xAB, 0x76,
    0xCA, 0x82, 0xC9, 0x7D, 0xFA, 0x59, 0x47, 0xF0, 0xAD, 0xD4, 0xA2, 0xAF, 0x9C, 0xA4, 0x72, 0xC0,
    0xB7, 0xFD, 0x93, 0x26, 0x36, 0x3F, 0xF7, 0xCC, 0x34, 0xA5, 0xE5, 0xF1, 0x71, 0xD8, 0x31, 0x15,
    0x04, 0xC7, 0x23, 0xC3, 0x18, 0x96, 0x05, 0x9A, 0x07, 0x12, 0x80, 0xE2, 0xEB, 0x27, 0xB2, 0x75,
    0x09, 0x83, 0x2C, 0x1A, 0x1B, 0x6E, 0x5A, 0xA0, 0x52, 0x3B, 0xD6, 0xB3, 0x29, 0xE3, 0x2F, 0x84,
    0x53, 0xD1, 0x00, 0xED, 0x20, 0xFC, 0xB1, 0x5B, 0x6A, 0xCB, 0xBE, 0x39, 0x4A, 0x4C, 0x58, 0xCF,
    0xD0, 0xEF, 0xAA, 0xFB, 0x43, 0x4D, 0x33, 0x85, 0x45, 0xF9, 0x02, 0x7F, 0x50, 0x3C, 0x9F, 0xA8,
    0x51, 0xA3, 0x40, 0x8F, 0x92, 0x9D, 0x38, 0xF5, 0xBC, 0xB6, 0xDA, 0x21, 0x10, 0xFF, 0xF3, 0xD2,
    0xCD, 0x0C, 0x13, 0xEC, 0x5F, 0x97, 0x44, 0x17, 0xC4, 0xA7, 0x7E, 0x3D, 0x64, 0x5D, 0x19, 0x73,
    0x60, 0x81, 0x4F, 0xDC, 0x22, 0x2A, 0x90, 0x88, 0x46, 0xEE, 0xB8, 0x14, 0xDE, 0x5E, 0x0B, 0xDB,
    0xE0, 0x32, 0x3A, 0x0A, 0x49, 0x06, 0x24, 0x5C, 0xC2, 0xD3, 0xAC, 0x62, 0x91, 0x95, 0xE4, 0x79,
    0xE7, 0xC8, 0x37, 0x6D, 0x8D, 0xD5, 0x4E, 0xA9, 0x6C, 0x56, 0xF4, 0xEA, 0x65, 0x7A, 0xAE, 0x08,
    0xBA, 0x78, 0x25, 0x2E, 0x1C, 0xA6, 0xB4, 0xC6, 0xE8, 0xDD, 0x74, 0x1F, 0x4B, 0xBD, 0x8B, 0x8A,
    0x70, 0x3E, 0xB5, 0x66, 0x48, 0x03, 0xF6, 0x0E, 0x61, 0x35, 0x57, 0xB9, 0x86, 0xC1, 0x1D, 0x9E,
    0xE1, 0xF8, 0x98, 0x11, 0x69, 0xD9, 0x8E, 0x94, 0x9B, 0x1E, 0x87, 0xE9, 0xCE, 0x55, 0x28, 0xDF,
    0x8C, 0xA1, 0x89, 0x0D, 0xBF, 0xE6, 0x42, 0x68, 0x41, 0x99, 0x2D, 0x0F, 0xB0, 0x54, 0xBB, 0x16};

const unsigned char rcon[256] = {
    0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a,
    0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39,
    0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a,
    0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8,
    0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef,
    0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc,
    0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b,
    0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3,
    0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94,
    0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20,
    0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35,
    0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f,
    0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04,
    0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63,
    0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd,
    0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d};

void addRoundKey(unsigned char *input, unsigned char *key)
{
    for (int i = 0; i < LENGTH; i++)
        input[i] ^= key[i];
}

void byteSubstituition(unsigned char *input)
{
    for (int i = 0; i < LENGTH; i++)
        input[i] = SBOX[input[i]];
}

void shiftRows(unsigned char *input)
{
    unsigned char result[16];

    result[0] = input[0];
    result[1] = input[5];
    result[2] = input[10];
    result[3] = input[15];

    result[4] = input[4];
    result[5] = input[9];
    result[6] = input[14];
    result[7] = input[3];

    result[8] = input[8];
    result[9] = input[13];
    result[10] = input[2];
    result[11] = input[7];

    result[12] = input[12];
    result[13] = input[1];
    result[14] = input[6];
    result[15] = input[11];

    for (int i = 0; i < LENGTH; i++)
        input[i] = result[i];
}

unsigned char mul3(unsigned char in)
{
    unsigned int res = (2 * in) ^ in;
    if (res >= 256)
        res = res ^ 0x1b;
    return res;
}

unsigned char mul2(unsigned char in)
{
    unsigned int res = (2 * in);
    if (res >= 256)
        res = res ^ 0x1b;
    return res;
}

void mixColumn(unsigned char *input)
{
    unsigned char result[LENGTH];

    for (int i = 0; i < 4; i++)
    {
        result[4 * i + 0] = (unsigned char)mul2(input[4 * i]) ^ mul3(input[4 * i + 1]) ^ input[4 * i + 2] ^ input[4 * i + 3];
        result[4 * i + 1] = (unsigned char)input[4 * i] ^ mul2(input[4 * i + 1]) ^ mul3(input[4 * i + 2]) ^ input[4 * i + 3];
        result[4 * i + 2] = (unsigned char)input[4 * i] ^ input[4 * i + 1] ^ mul2(input[4 * i + 2]) ^ mul3(input[4 * i + 3]);
        result[4 * i + 3] = (unsigned char)mul3(input[4 * i]) ^ input[4 * i + 1] ^ input[4 * i + 2] ^ mul2(input[4 * i + 3]);
    }

    for (int i = 0; i < LENGTH; i++)
        input[i] = result[i];
}

void diffusion(unsigned char *input)
{
    shiftRows(input);
    mixColumn(input);
}

void round(unsigned char *input, unsigned char *key)
{
    byteSubstituition(input);
    diffusion(input);
    addRoundKey(input, key);
}

void encryptSbox(unsigned char *input, unsigned char *extendedKey)
{

    //ROUND 0
    addRoundKey(input, extendedKey);

    for (int i = 1; i < ROUND; i++)
        round(input, extendedKey + 16 * i);

    //ROUND 10
    byteSubstituition(input);
}

unsigned int ascii2hex(unsigned char b)
{
    if (b >= 'a')
        return 10 + b - 'a';
    if (b >= 'A')
        return 10 + b - 'A';
    return b - '0';
}

void f(unsigned char *extendedKey, int index)
{
    extendedKey[(index + 1) * 4] = SBOX[extendedKey[index * 4 + 1]] ^ rcon[((index + 1) / 4)];
    extendedKey[(index + 1) * 4 + 1] = SBOX[extendedKey[index * 4 + 2]];
    extendedKey[(index + 1) * 4 + 2] = SBOX[extendedKey[index * 4 + 3]];
    extendedKey[(index + 1) * 4 + 3] = SBOX[extendedKey[index * 4]];
}

void extendKey(unsigned char *key, unsigned char *extendedKey)
{
    for (int i = 0; i < LENGTH; i++)
        extendedKey[i] = key[i];
    for (int i = 1; i <= ROUND; i++)
    {
        int w_index = i * 4;
        f(extendedKey, w_index - 1);
        for (int j = 0; j < 4; j++)
            extendedKey[w_index * 4 + j] ^= extendedKey[(w_index - 4) * 4 + j];

        for (int k = 0; k < 4 - 1; k++)
        {
            w_index++;
            for (int j = 0; j < 4; j++)
                extendedKey[w_index * 4 + j] = extendedKey[(w_index - 4) * 4 + j] ^ extendedKey[(w_index - 1) * 4 + j];
        }
    }
}

void print_in_hex(unsigned char a)
{
    unsigned char first = (a / 16) > 9 ? 'a' + (a / 16) - 10 : '0' + (a / 16);
    cout << hex << first;
    unsigned char second = (a % 16) > 9 ? 'a' + (a % 16) - 10 : '0' + (a % 16);
    cout << hex << second;
}

int main()
{
    unsigned char key_in[LENGTH * 2 + 1];
    unsigned char plain_in[LENGTH * 2 + 1];

    cin >> key_in >> plain_in;

    unsigned char input[LENGTH];
    unsigned char key[LENGTH], extendedKey[LENGTH * (ROUND + 1)];

    for (int i = 0; i < LENGTH; i++)
    {
        input[i] = ascii2hex(plain_in[i * 2]) * 16 + ascii2hex(plain_in[i * 2 + 1]);
        key[i] = ascii2hex(key_in[i * 2]) * 16 + ascii2hex(key_in[i * 2 + 1]);
    }

    extendKey(key, extendedKey);

    encryptSbox(input, extendedKey);
    cout<<"Encrypting with S-Box of AES ALgorithm \n";

    for (int i = 0; i < LENGTH; i++)
    {
        print_in_hex(input[i]);
    }
    cout << endl;
}