Why Is My Java 3DES Encryption/Decryption Failing?

Troubleshooting 3DES Encryption/Decryption in Java

Problem:

Unable to successfully encrypt and decrypt a string using 3DES encryption due to recurring errors in code implementation.

Solution:

To address the issue, let's analyze the provided code:

public class TripleDESTest {

    // ...

    public byte[] encrypt(String message) {
        // ...

        final byte[] plainTextBytes = message.getBytes("utf-8");
        final byte[] cipherText = cipher.doFinal(plainTextBytes);
        final String encodedCipherText = new sun.misc.BASE64Encoder().encode(cipherText);

        return cipherText;    
    }

    // ...
}

Base64 Encoding Misconception:

Initially, the code included the line final String encodedCipherText = new sun.misc.BASE64Encoder().encode(cipherText); for Base64 encoding the ciphertext before returning it. However, since Base64 encoding wasn't being used in the decryption method, the ciphertext should be returned directly as a byte array.

Printing Raw Byte Arrays:

The code prints both the encrypted and decrypted data as byte arrays: System.out.println(codedtext); and System.out.println(decodedtext);. This doesn't provide meaningful output as byte arrays don't render as human-readable values. To display the actual decrypted text, convert it to a string using new String(plainText, "UTF-8").

Corrected Code:

import java.security.MessageDigest;
import java.util.Arrays;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class TripleDESTest {

    public static void main(String[] args) throws Exception {

        String text = "kyle boon";

        byte[] codedtext = new TripleDESTest().encrypt(text);
        String decodedtext = new TripleDESTest().decrypt(codedtext);

        System.out.println(decodedtext);
    }

    public byte[] encrypt(String message) throws Exception {
        final MessageDigest md = MessageDigest.getInstance("md5");
        final byte[] digestOfPassword = md.digest("HG58YZ3CR9"
                .getBytes("utf-8"));
        final byte[] keyBytes = Arrays.copyOf(digestOfPassword, 24);
        for (int j = 0, k = 16; j < 8;) {
            keyBytes[k++] = keyBytes[j++];
        }

        final SecretKey key = new SecretKeySpec(keyBytes, "DESede");
        final IvParameterSpec iv = new IvParameterSpec(new byte[8]);
        final Cipher cipher = Cipher.getInstance("DESede/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, key, iv);

        final byte[] plainTextBytes = message.getBytes("utf-8");
        final byte[] cipherText = cipher.doFinal(plainTextBytes);

        return cipherText;
    }

    public String decrypt(byte[] message) throws Exception {
        final MessageDigest md = MessageDigest.getInstance("md5");
        final byte[] digestOfPassword = md.digest("HG58YZ3CR9"
                .getBytes("utf-8"));
        final byte[] keyBytes = Arrays.copyOf(digestOfPassword, 24);
        for (int j = 0, k = 16; j < 8;) {
            keyBytes[k++] = keyBytes[j++];
        }

        final SecretKey key = new SecretKeySpec(keyBytes, "DESede");
        final IvParameterSpec iv = new IvParameterSpec(new byte[8]);
        final Cipher decipher = Cipher.getInstance("DESede/CBC/PKCS5Padding");
        decipher.init(Cipher.DECRYPT_MODE, key, iv);

        final byte[] plainText = decipher.doFinal(message);

        return new String(plainText, "UTF-8");
    }
}

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