Have a problem when encrypt by RSA

[ba thong]

I have a method

public static byte[] EncryptByPublicKey(byte[] text, PublicKey key) {
        //byte[] encryptText = null;
 
        try {
            Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
            cipher.init(Cipher.ENCRYPT_MODE, key);
            return cipher.doFinal(text);
        }
        catch (Exception e){
            System.out.println("Err " + e.toString());
        }
 
        return null;
    }

I write a class test this method

public static void main(String[] args){
        PublicKey pub = ReadPublicKey("publicReceiver.k");
 
        String message = "abc";
 
        String encryptText = 
                    new String(EncryptByPublicKey(message.getBytes(), pub));
        System.out.println(encryptText);
 
    }

when I execute the minutes each are different results for each
help me please, thanks a lot of

[Ulf Dittmer]

Does "ReadPublicKey("publicReceiver.k")" return the same result each time it is called? If not, then all bets are off.

Note that encrypted stuff is binary data, not text - so an operation like "new String(encrypted stuff)" does not make sense, and will lead to unexpected results.

What do you mean by "when I execute the minutes" - are you running this code several times within a few minutes, or what?

[ba thong]

Ulf Dittmer wrote:Does "ReadPublicKey("publicReceiver.k")" return the same result each time it is called? If not, then all bets are off.

Ok it here

public static PublicKey ReadPublicKey(String filename){
        try {
            ObjectInputStream objInput =
                    new ObjectInputStream( new BufferedInputStream(new FileInputStream(filename)));

            BigInteger m = (BigInteger)objInput.readObject();
            BigInteger e = (BigInteger)objInput.readObject();
            /*
            System.out.println("---Public Key");
            System.out.println("m " + m);
            System.out.println("e " + e);*/
            
            RSAPublicKeySpec pub = new RSAPublicKeySpec(m, e);
            
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            PublicKey publicKey = keyFactory.generatePublic(pub);
            return publicKey;
        }
        catch (Exception exp){
            System.out.println("Err " + exp.toString());
            return null;
        }
    }

Note that encrypted stuff is binary data, not text - so an operation like "new String(encrypted stuff)" does not make sense, and will lead to unexpected results.

I have two method so that show result encrypt and decrypt format String

public static String ArrayByteToString(byte[] bytes)
    {
        BASE64Encoder b64 = new BASE64Encoder();
        return b64.encode(bytes);
    }

    public static byte[] StringToArrayByte(String text) throws IOException
    {
        BASE64Decoder b64 = new BASE64Decoder();
        return b64.decodeBuffer(text);
    }

I continue test, when i write

public static void main(String[] args){
        PublicKey pub = ReadPublicKey("publicReceiver.k");

        String message = "abc";

        byte[] data1 = EncryptByPublicKey(message.getBytes(), pub);
        System.out.println(ArrayByteToString(data1));

        byte[] data2 = EncryptByPublicKey(message.getBytes(), pub);
        System.out.println(ArrayByteToString(data2));

        
    }

The result is data1 unlike data2 !! Why ??? hixhix.