Hello..it’s been a long time since my last post. Actually i am a bit busy with my project going to ITEX exhibition this friday.

Now i am going to share with you all an example of AES encryption. This AES encryption used password from user as a key. Firstly, let me tell you more about AES.

Strictly speaking, AES is not precisely Rijndael (although in practice they are used interchangeably) as Rijndael supports a larger range of block and key sizes; AES has a fixed block size of 128 bits and a key size of 128, 192, or 256 bits, whereas Rijndael can be specified with key and block sizes in any multiple of 32 bits, with a minimum of 128 bits and a maximum of 256 bits.

Due to the fixed block size of 128 bits, AES operates on a 4×4 array of bytes, termed the state (versions of Rijndael with a larger block size have additional columns in the state). Most AES calculations are done in a special finite field. [source: wikipedia]

PKCS5S2ParametersGenerator generator = new PKCS5S2ParametersGenerator();

byte[] salt = {
(byte)0xc7, (byte)0×73, (byte)0×21, (byte)0×8c,
(byte)0×7e, (byte)0xc8, (byte)0xee, (byte)0×99,
(byte)0xc7, (byte)0×73, (byte)0×21, (byte)0×8c,
(byte)0×7e, (byte)0xc8, (byte)0xee, (byte)0×99
};

int count = 16;

IvParameterSpec iv = new IvParameterSpec(salt);

generator.init(pBytes, salt, count);

ParametersWithIV params = (ParametersWithIV)
generator.generateDerivedParameters(128, 128);

KeyParameter keyParam = (KeyParameter) params.getParameters();

SecretKeySpec key = new SecretKeySpec(keyParam.getKey(), “AES”);

String password = “secretkey”;
String PT = “Attack at dawn”;

byte[] pBytes = password.getBytes();

Cipher cipher = Cipher.getInstance(”AES/CBC/PKCS5Padding”,”BC”);
cipher.init(Cipher.ENCRYPT_MODE,key,iv);

byte[] cipherText = cipher.doFinal(PT.getBytes(”ASCII”));
Base64 b64 = new Base64();

String b64ctxt = new String(Base64.encode(cipherText), “ASCII”);
String b64key = new String(Base64.encode(key.getEncoded()), “ASCII”);

System.out.println(”Ciphertext = ” + b64ctxt);
System.out.println(”B64 key = ” + b64key);

byte[] newCtxt = Base64.decode(b64ctxt);
cipher.init(Cipher.DECRYPT_MODE, key,iv);
byte[] plainBytes = cipher.doFinal(newCtxt);
String newPlainText = new String(plainBytes, “ASCII”);
System.out.println(”Plaintext = [” + newPlainText + “]”);

Thats all folks..Hope this would help. Just drop a comment if something is not right about the coding.