javax.crypto.IllegalBlockSizeException: Input length not multiple of 8 bytes

Question

i am getting this error while decryption i have go through the similar posts but i did not get any help from there. I want to store an object directly in a file with encryption for that i have posted my question here. But while using stream i am getting the same error as i am getting with string.

package security;

import java.security.spec.KeySpec;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESedeKeySpec;
import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

/**
 * This class defines methods for encrypting and decrypting using the Triple DES
 * algorithm and for generating, reading and writing Triple DES keys. It also
 * defines a main() method that allows these methods to be used from the command
 * line.
 */
public class TripleDesEncryptionDecryption {
  /**
   * The program. The first argument must be -e, -d, or -g to encrypt,
   * decrypt, or generate a key. The second argument is the name of a file
   * from which the key is read or to which it is written for -g. The -e and
   * -d arguments cause the program to read from standard input and encrypt or
   * decrypt to standard output.
   */
    private static final String UNICODE_FORMAT = "UTF-8";
    public static final String DESEDE_ENCRYPTION_SCHEME = "DESede";
    private KeySpec myKeySpec;
    private SecretKeyFactory mySecretKeyFactory;
    private Cipher cipher;
    byte[] keyAsBytes;
    private String myEncryptionKey;
    private String myEncryptionScheme;
    SecretKey key;
    static String stringToEncrypt="";

    public void setKey(String myKey) throws Exception
    {
        myEncryptionKey = myKey ;
        myEncryptionScheme = DESEDE_ENCRYPTION_SCHEME;
        keyAsBytes = myEncryptionKey.getBytes(UNICODE_FORMAT);
        myKeySpec = new DESedeKeySpec(keyAsBytes);
        mySecretKeyFactory = SecretKeyFactory.getInstance(myEncryptionScheme);
        cipher = Cipher.getInstance("DESede/ECB/NoPadding");
        key = mySecretKeyFactory.generateSecret(myKeySpec);
    }

    /**
     * Method To Encrypt The String
     */
    public String encrypt(byte[] plainText) {
        String encryptedString = null;
        try {
            cipher.init(Cipher.ENCRYPT_MODE, key);
            //byte[] plainText = unencryptedString.getBytes(UNICODE_FORMAT);
            //byte[] encryptedText = cipher.doFinal(plainText);
            BASE64Encoder base64encoder = new BASE64Encoder();
            encryptedString = base64encoder.encode(plainText);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return encryptedString;
    }
    /**
     * Method To Decrypt An Ecrypted String
     */
    public String decrypt(String encryptedString) {
        String decryptedText=null;
        try {
            cipher.init(Cipher.DECRYPT_MODE, key);
            BASE64Decoder base64decoder = new BASE64Decoder();
            System.out.println(myEncryptionKey);
            byte[] encryptedText = base64decoder.decodeBuffer(encryptedString);
            byte[] plainText = cipher.doFinal(encryptedText);
            decryptedText= bytes2String(plainText);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return decryptedText;
    }
    /**
     * Returns String From An Array Of Bytes
     */
    private static String bytes2String(byte[] bytes) {
        StringBuffer stringBuffer = new StringBuffer();
        for (int i = 0; i < bytes.length; i++) {
            stringBuffer.append((char) bytes[i]);
        }
        return stringBuffer.toString();
    }

    /**
     * Testing The DESede Encryption And Decryption Technique
    */
    public static void main(String args []) throws Exception
    {
        TripleDesEncryptionDecryption myEncryptor= new TripleDesEncryptionDecryption();


        myEncryptor.setKey("[email protected]") ;

        System.out.println("tarun1234".getBytes());
        String encrypted=myEncryptor.encrypt("tarun".getBytes());
        String decrypted=myEncryptor.decrypt(encrypted);

        System.out.println("String To Encrypt: "+stringToEncrypt);
        System.out.println("Encrypted Value :" + encrypted);
        System.out.println("Decrypted Value :"+decrypted);
    }
}

Answer 1

I don't exactly know what you want to achieve, but I can at least explain the error you are getting.

DES and 3DES have a block-length of 64 bit. That means you must pass a plaintext which length is a multiple of 64-bits to the encryption-function. To achieve this you usually pad / fill up the last block of the plaintext with data of a certain pattern so that you can easily remove it again after decryption.

In your code you specify the encryption-parameters like this: DESede/ECB/NoPadding
So you explicitly opt to not automatically apply any padding.

---

To fix this, just specify a padding mode (for example PKCS5Padding) instead of NoPadding.

Note: The cipher-mode ECB is not secure at all! You should instead better use:

Cipher.getInstance("DESede/CBC/PKCS5Padding"); // or "AES" instead of "DESede"

(you must provide an additional IV though when using a mode like CBC or CTR)