Memodifikasi Sbox pada algoritma GOST28147 provider BC


Salah satu parameter dalam Algoritma GOST28147 adalah Sbox, Sbox bisa bersifat secret ataupun open. Didalam algoritma GOST28147 yang disediakan oleh provider BC terdapat beberapa alternatif SBOX seperti yang terdapat didalam
GOST28147Engine.java, kita dapat melihatnya dari baris 22 sampai 116 pada class tersebut. Scriptnya sebagai berikut:

    // these are the S-boxes given in Applied Cryptography 2nd Ed., p. 333
    // This is default S-box!
    private byte S[] = {
        0x4,0xA,0x9,0x2,0xD,0x8,0x0,0xE,0x6,0xB,0x1,0xC,0x7,0xF,0x5,0x3,
        0xE,0xB,0x4,0xC,0x6,0xD,0xF,0xA,0x2,0x3,0x8,0x1,0x0,0x7,0x5,0x9,
        0x5,0x8,0x1,0xD,0xA,0x3,0x4,0x2,0xE,0xF,0xC,0x7,0x6,0x0,0x9,0xB,
        0x7,0xD,0xA,0x1,0x0,0x8,0x9,0xF,0xE,0x4,0x6,0xC,0xB,0x2,0x5,0x3,
        0x6,0xC,0x7,0x1,0x5,0xF,0xD,0x8,0x4,0xA,0x9,0xE,0x0,0x3,0xB,0x2,
        0x4,0xB,0xA,0x0,0x7,0x2,0x1,0xD,0x3,0x6,0x8,0x5,0x9,0xC,0xF,0xE,
        0xD,0xB,0x4,0x1,0x3,0xF,0x5,0x9,0x0,0xA,0xE,0x7,0x6,0x8,0x2,0xC,
        0x1,0xF,0xD,0x0,0x5,0x7,0xA,0x4,0x9,0x2,0x3,0xE,0x6,0xB,0x8,0xC
    };
    
    /*
     * class content S-box parameters for encrypting
     * getting from, see: http://www.ietf.org/internet-drafts/draft-popov-cryptopro-cpalgs-01.txt
     *                    http://www.ietf.org/internet-drafts/draft-popov-cryptopro-cpalgs-02.txt
     */
    private static byte[] ESbox_Test = {
         0x4,0x2,0xF,0x5,0x9,0x1,0x0,0x8,0xE,0x3,0xB,0xC,0xD,0x7,0xA,0x6,
         0xC,0x9,0xF,0xE,0x8,0x1,0x3,0xA,0x2,0x7,0x4,0xD,0x6,0x0,0xB,0x5,
         0xD,0x8,0xE,0xC,0x7,0x3,0x9,0xA,0x1,0x5,0x2,0x4,0x6,0xF,0x0,0xB,
         0xE,0x9,0xB,0x2,0x5,0xF,0x7,0x1,0x0,0xD,0xC,0x6,0xA,0x4,0x3,0x8,
         0x3,0xE,0x5,0x9,0x6,0x8,0x0,0xD,0xA,0xB,0x7,0xC,0x2,0x1,0xF,0x4,
         0x8,0xF,0x6,0xB,0x1,0x9,0xC,0x5,0xD,0x3,0x7,0xA,0x0,0xE,0x2,0x4,
         0x9,0xB,0xC,0x0,0x3,0x6,0x7,0x5,0x4,0x8,0xE,0xF,0x1,0xA,0x2,0xD,
         0xC,0x6,0x5,0x2,0xB,0x0,0x9,0xD,0x3,0xE,0x7,0xA,0xF,0x4,0x1,0x8
    };
    
    private static byte[] ESbox_A = {
         0x9,0x6,0x3,0x2,0x8,0xB,0x1,0x7,0xA,0x4,0xE,0xF,0xC,0x0,0xD,0x5,
         0x3,0x7,0xE,0x9,0x8,0xA,0xF,0x0,0x5,0x2,0x6,0xC,0xB,0x4,0xD,0x1,
         0xE,0x4,0x6,0x2,0xB,0x3,0xD,0x8,0xC,0xF,0x5,0xA,0x0,0x7,0x1,0x9,
         0xE,0x7,0xA,0xC,0xD,0x1,0x3,0x9,0x0,0x2,0xB,0x4,0xF,0x8,0x5,0x6,
         0xB,0x5,0x1,0x9,0x8,0xD,0xF,0x0,0xE,0x4,0x2,0x3,0xC,0x7,0xA,0x6,
         0x3,0xA,0xD,0xC,0x1,0x2,0x0,0xB,0x7,0x5,0x9,0x4,0x8,0xF,0xE,0x6,
         0x1,0xD,0x2,0x9,0x7,0xA,0x6,0x0,0x8,0xC,0x4,0x5,0xF,0x3,0xB,0xE,
         0xB,0xA,0xF,0x5,0x0,0xC,0xE,0x8,0x6,0x2,0x3,0x9,0x1,0x7,0xD,0x4
    };
    
    private static byte[] ESbox_B = {
         0x8,0x4,0xB,0x1,0x3,0x5,0x0,0x9,0x2,0xE,0xA,0xC,0xD,0x6,0x7,0xF,
         0x0,0x1,0x2,0xA,0x4,0xD,0x5,0xC,0x9,0x7,0x3,0xF,0xB,0x8,0x6,0xE,
         0xE,0xC,0x0,0xA,0x9,0x2,0xD,0xB,0x7,0x5,0x8,0xF,0x3,0x6,0x1,0x4,
         0x7,0x5,0x0,0xD,0xB,0x6,0x1,0x2,0x3,0xA,0xC,0xF,0x4,0xE,0x9,0x8,
         0x2,0x7,0xC,0xF,0x9,0x5,0xA,0xB,0x1,0x4,0x0,0xD,0x6,0x8,0xE,0x3,
         0x8,0x3,0x2,0x6,0x4,0xD,0xE,0xB,0xC,0x1,0x7,0xF,0xA,0x0,0x9,0x5,
         0x5,0x2,0xA,0xB,0x9,0x1,0xC,0x3,0x7,0x4,0xD,0x0,0x6,0xF,0x8,0xE,
         0x0,0x4,0xB,0xE,0x8,0x3,0x7,0x1,0xA,0x2,0x9,0x6,0xF,0xD,0x5,0xC
    };
    
    private static byte[] ESbox_C = {
         0x1,0xB,0xC,0x2,0x9,0xD,0x0,0xF,0x4,0x5,0x8,0xE,0xA,0x7,0x6,0x3,
         0x0,0x1,0x7,0xD,0xB,0x4,0x5,0x2,0x8,0xE,0xF,0xC,0x9,0xA,0x6,0x3,
         0x8,0x2,0x5,0x0,0x4,0x9,0xF,0xA,0x3,0x7,0xC,0xD,0x6,0xE,0x1,0xB,
         0x3,0x6,0x0,0x1,0x5,0xD,0xA,0x8,0xB,0x2,0x9,0x7,0xE,0xF,0xC,0x4,
         0x8,0xD,0xB,0x0,0x4,0x5,0x1,0x2,0x9,0x3,0xC,0xE,0x6,0xF,0xA,0x7,
         0xC,0x9,0xB,0x1,0x8,0xE,0x2,0x4,0x7,0x3,0x6,0x5,0xA,0x0,0xF,0xD,
         0xA,0x9,0x6,0x8,0xD,0xE,0x2,0x0,0xF,0x3,0x5,0xB,0x4,0x1,0xC,0x7,
         0x7,0x4,0x0,0x5,0xA,0x2,0xF,0xE,0xC,0x6,0x1,0xB,0xD,0x9,0x3,0x8
    };
    
    private static byte[] ESbox_D = {
         0xF,0xC,0x2,0xA,0x6,0x4,0x5,0x0,0x7,0x9,0xE,0xD,0x1,0xB,0x8,0x3,
         0xB,0x6,0x3,0x4,0xC,0xF,0xE,0x2,0x7,0xD,0x8,0x0,0x5,0xA,0x9,0x1,
         0x1,0xC,0xB,0x0,0xF,0xE,0x6,0x5,0xA,0xD,0x4,0x8,0x9,0x3,0x7,0x2,
         0x1,0x5,0xE,0xC,0xA,0x7,0x0,0xD,0x6,0x2,0xB,0x4,0x9,0x3,0xF,0x8,
         0x0,0xC,0x8,0x9,0xD,0x2,0xA,0xB,0x7,0x3,0x6,0x5,0x4,0xE,0xF,0x1,
         0x8,0x0,0xF,0x3,0x2,0x5,0xE,0xB,0x1,0xA,0x4,0x7,0xC,0x9,0xD,0x6,
         0x3,0x0,0x6,0xF,0x1,0xE,0x9,0x2,0xD,0x8,0xC,0x4,0xB,0xA,0x5,0x7,
         0x1,0xA,0x6,0x8,0xF,0xB,0x0,0x4,0xC,0x3,0x5,0x9,0x7,0xD,0x2,0xE
    };
    
    //S-box for digest
    private static byte DSbox_Test[] = {
         0x4,0xA,0x9,0x2,0xD,0x8,0x0,0xE,0x6,0xB,0x1,0xC,0x7,0xF,0x5,0x3,
         0xE,0xB,0x4,0xC,0x6,0xD,0xF,0xA,0x2,0x3,0x8,0x1,0x0,0x7,0x5,0x9,
         0x5,0x8,0x1,0xD,0xA,0x3,0x4,0x2,0xE,0xF,0xC,0x7,0x6,0x0,0x9,0xB,
         0x7,0xD,0xA,0x1,0x0,0x8,0x9,0xF,0xE,0x4,0x6,0xC,0xB,0x2,0x5,0x3,
         0x6,0xC,0x7,0x1,0x5,0xF,0xD,0x8,0x4,0xA,0x9,0xE,0x0,0x3,0xB,0x2,
         0x4,0xB,0xA,0x0,0x7,0x2,0x1,0xD,0x3,0x6,0x8,0x5,0x9,0xC,0xF,0xE,
         0xD,0xB,0x4,0x1,0x3,0xF,0x5,0x9,0x0,0xA,0xE,0x7,0x6,0x8,0x2,0xC,
         0x1,0xF,0xD,0x0,0x5,0x7,0xA,0x4,0x9,0x2,0x3,0xE,0x6,0xB,0x8,0xC
    };
    
    private static byte DSbox_A[] = {
         0xA,0x4,0x5,0x6,0x8,0x1,0x3,0x7,0xD,0xC,0xE,0x0,0x9,0x2,0xB,0xF,
         0x5,0xF,0x4,0x0,0x2,0xD,0xB,0x9,0x1,0x7,0x6,0x3,0xC,0xE,0xA,0x8,
         0x7,0xF,0xC,0xE,0x9,0x4,0x1,0x0,0x3,0xB,0x5,0x2,0x6,0xA,0x8,0xD,
         0x4,0xA,0x7,0xC,0x0,0xF,0x2,0x8,0xE,0x1,0x6,0x5,0xD,0xB,0x9,0x3,
         0x7,0x6,0x4,0xB,0x9,0xC,0x2,0xA,0x1,0x8,0x0,0xE,0xF,0xD,0x3,0x5,
         0x7,0x6,0x2,0x4,0xD,0x9,0xF,0x0,0xA,0x1,0x5,0xB,0x8,0xE,0xC,0x3,
         0xD,0xE,0x4,0x1,0x7,0x0,0x5,0xA,0x3,0xC,0x8,0xF,0x6,0x2,0x9,0xB,
         0x1,0x3,0xA,0x9,0x5,0xB,0x4,0xF,0x8,0x6,0x7,0xE,0xD,0x0,0x2,0xC
    };

Bagaimana kita dapat menggunakan Sbox tersebut?, secara default Sbox yang digunakan adalah SBox private byte S[]. Seperti Script dibawah ini yang menggunakan Sbox default:

public class Gost_ChangeSbox {
	public static void main (String[] args) throws NoSuchAlgorithmException, NoSuchProviderException, NoSuchPaddingException, InvalidKeyException, ShortBufferException, IllegalBlockSizeException, BadPaddingException, InvalidAlgorithmParameterException {
		byte[]        input = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07};
		//GOST
				byte[] keyBytes = new byte[] { 
		        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
				}; //256 bytes
		        SecretKeySpec key = new SecretKeySpec(keyBytes, "GOST28147");
		      
      
        Cipher        cipher = Cipher.getInstance("GOST28147/ECB/NoPadding","BC");
        // encryption pass
        cipher.init(Cipher.ENCRYPT_MODE, key);
        byte[] cipherText = new byte[cipher.getOutputSize(input.length)];
        int ctLength = cipher.update(input, 0, input.length, cipherText, 0);
        ctLength += cipher.doFinal(cipherText, ctLength);
       
        // decryption pass
        cipher.init(Cipher.DECRYPT_MODE, key);
        byte[] plainText = new byte[cipher.getOutputSize(ctLength)];
        int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0);  
        ptLength += cipher.doFinal(plainText, ptLength);
      
	}
}

kita ingin menggunakan Sbox ESbox_A, maka kita perlu mengeset parameter terlebih dahulu, perhatikan script lengkapnya sebagai berikut:

public class Gost_ChangeSbox {
	public static void main (String[] args) throws NoSuchAlgorithmException, NoSuchProviderException, NoSuchPaddingException, InvalidKeyException, ShortBufferException, IllegalBlockSizeException, BadPaddingException, InvalidAlgorithmParameterException {
		byte[]        input = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07};
		//GOST
				byte[] keyBytes = new byte[] { 
		        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
				}; //256 bytes
		        SecretKeySpec key = new SecretKeySpec(keyBytes, "GOST28147");
		       
        Cipher        cipher = Cipher.getInstance("GOST28147/ECB/NoPadding","BC");
       
        // encryption pass
        GOST28147ParameterSpec paramss = new GOST28147ParameterSpec (GOST28147Engine.getSBox("E-A"));
        
        cipher.init(Cipher.ENCRYPT_MODE, key, paramss);
        //cipher.init(Cipher.ENCRYPT_MODE, key);
        byte[] cipherText = new byte[cipher.getOutputSize(input.length)];
        int ctLength = cipher.update(input, 0, input.length, cipherText, 0);
        ctLength += cipher.doFinal(cipherText, ctLength);
        
        // decryption pass
        cipher.init(Cipher.DECRYPT_MODE, key, paramss);
        byte[] plainText = new byte[cipher.getOutputSize(ctLength)];
        int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0);  
        ptLength += cipher.doFinal(plainText, ptLength);
       
	}
}


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Author: ridhobustami

orang ngak jelas

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