Friday, April 27, 2012

Java : Simple AES Cryptography example

Advanced Encryption Standard (AES) is a specification for the encryption of electronic data. It has been adopted by the U.S. government and is now used worldwide. It supersedes DES.[3] The algorithm described by AES is a symmetric-key algorithm, meaning the same key is used for both encrypting and decrypting the data. (To know more click here).

To run this example you will need below mentioned JAR files in classpath.
  • jce.jar
  • rt.jar

If you are using JDK 6 or higher version, These JAR files are implicitly present. You can cross verify in JRE folder. Probably in "C:\Program Files\Java\jre6\lib"

Hence C:\Program Files\Java\jre6\lib\jce.jar and C:\Program Files\Java\jre6\lib\rt.jar are implicitly set in your classpath. Below is the sample self explanatory Java program using AES Cipher. Directly you can run the program and see output.

Simple AES Cipher Example in java

/* SimpleCryptography.java */

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

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

public class SimpleCryptography {
    
    private String AlgoName = "AES";
    
    private String keyString = "Desire_SecretKey";
    
    public String encrypt(String sValue) throws Exception {
        
        SecretKeySpec skeySpec = new SecretKeySpec(keyString.getBytes(), AlgoName);
        Cipher cipher = Cipher.getInstance(AlgoName);
        
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        
        byte[] encrypted = cipher.doFinal(sValue.getBytes());
        
        BASE64Encoder bASE64Encoder = new BASE64Encoder();
        String enStr = bASE64Encoder.encodeBuffer(encrypted);    
        
        return enStr;
    }
    
    public String decrypt(String sValue) throws Exception {
        
        SecretKeySpec skeySpec = new SecretKeySpec(keyString.getBytes(), AlgoName);
        Cipher cipher = Cipher.getInstance(AlgoName);
        
        BASE64Decoder bASE64Decoder = new BASE64Decoder();
        byte decrytByt[] = bASE64Decoder.decodeBuffer(sValue);
        
        cipher.init(Cipher.DECRYPT_MODE, skeySpec);
        
        byte decrypted[] = cipher.doFinal(decrytByt);
        
        String deStr = new String(decrypted).trim();
        
        return deStr;
    }
    
    public static void main(String[] args) throws Exception {
        
        SimpleCryptography obj = new SimpleCryptography();
        
        String password = "MadanChaudhary";
        
        System.out.println("password : "+password);
        
        String encrypted_password = obj.encrypt(password);
        
        System.out.println("encrypted_password : "+encrypted_password);
        
        String decrypted_password = obj.decrypt(encrypted_password);
        
        System.out.println("decrypted_password : "+decrypted_password);

    }
}

Output :

password : MadanChaudhary
encrypted_password : F3VWPvsjsaqsqpMgBnxp/w==

decrypted_password : MadanChaudhary

Note : While compiling you may get below warnings, please ignore this for now.

SimpleCryptography.java:6: warning: sun.misc.BASE64Decoder is Sun proprietary AP
I and may be removed in a future release
import sun.misc.BASE64Decoder;
               ^
SimpleCryptography.java:7: warning: sun.misc.BASE64Encoder is Sun proprietary AP
I and may be removed in a future release
import sun.misc.BASE64Encoder;
               ^
SimpleCryptography.java:24: warning: sun.misc.BASE64Encoder is Sun proprietary A
PI and may be removed in a future release
        BASE64Encoder bASE64Encoder = new BASE64Encoder();
        ^
SimpleCryptography.java:24: warning: sun.misc.BASE64Encoder is Sun proprietary A
PI and may be removed in a future release
        BASE64Encoder bASE64Encoder = new BASE64Encoder();
                                          ^
SimpleCryptography.java:35: warning: sun.misc.BASE64Decoder is Sun proprietary A
PI and may be removed in a future release
        BASE64Decoder bASE64Decoder = new BASE64Decoder();
        ^
SimpleCryptography.java:35: warning: sun.misc.BASE64Decoder is Sun proprietary A
PI and may be removed in a future release
        BASE64Decoder bASE64Decoder = new BASE64Decoder();
                                          ^
6 warnings

Also if your AES key is invalid you may get below error.

Exception in thread "main" java.security.InvalidKeyException: Invalid AES key length: 15 bytes
        at com.sun.crypto.provider.AESCipher.engineGetKeySize(DashoA13*..)
        at javax.crypto.Cipher.b(DashoA13*..)
        at javax.crypto.Cipher.a(DashoA13*..)
        at javax.crypto.Cipher.a(DashoA13*..)
        at javax.crypto.Cipher.a(DashoA13*..)
        at javax.crypto.Cipher.init(DashoA13*..)
        at javax.crypto.Cipher.init(DashoA13*..)
        at SimpleCryptography.encrypt(SimpleCryptography.java:20)
        at SimpleCryptography.main(SimpleCryptography.java:55)

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