javax.crypto.Cipher - How to obtain cipher text contaning the first 128 ASCII characters

Question

I have a requirement to implement in Java a method which takes a encrypts a String using AES128. (I am not interested in decrypting the output.) In order to implement this I have modified the example given here. Java AES 256 encryption

Here is my current implementation.

package com.test.demo;

import java.security.InvalidKeyException;
import java.security.Key;
import java.security.NoSuchAlgorithmException;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.SecretKeySpec;
import javax.xml.bind.DatatypeConverter;

import org.apache.commons.codec.binary.Base64;
import org.apache.log4j.Logger;

public class StringEncryptor {

    private static final Logger LOGGER = Logger.getLogger(StringEncryptor.class);

    public static String getEncryptedString(String input){

        if(input == null){
            return null;
        }

        String keyString = "C0BAE23DF8B51807B3E17D21925FADF2";//32 byte string
        byte[] keyValue = DatatypeConverter.parseHexBinary(keyString);
        Key key = new SecretKeySpec(keyValue, "AES");
        Cipher c1 = null;
        try {
            c1 = Cipher.getInstance("AES");
        } catch (NoSuchAlgorithmException | NoSuchPaddingException e) {
            LOGGER.error("error getting cypher", e);
            return null;
        }
        try {
            c1.init(Cipher.ENCRYPT_MODE, key);
        } catch (InvalidKeyException e) {
            LOGGER.error("error initalising cypher", e);
            return null;
        }

        byte[] encVal = null;
        try {
            encVal = c1.doFinal(input.getBytes());
        } catch (IllegalBlockSizeException | BadPaddingException e) {
            LOGGER.error("error performing encryption", e);
            return null;
        }
        String encryptedValue = Base64.encodeBase64String(encVal);

        return encryptedValue;
    }
}

The problem is, on examining test output, the String only contains characters [a-zA-Z+/]. I want my encrypted String to contain the full range of the first 128 ASCII characters.

I would be grateful for any suggestions. Many thanks.

score 1 · Accepted Answer · answered Jul 08 '15 at 16:07

You are using Base64 to encode your text, which uses only 64 ASCII characters.

I don't know of any popular encoding that uses the first 128 characters, since that would imply the use of the ASCII NUL character and various other control characters. If you are OK with just a plain binary string, you can simply remove the line

String encryptedValue = Base64.encodeBase64String(encVal);

javax.crypto.Cipher - How to obtain cipher text contaning the first 128 ASCII characters

1 Answers1