Bouncy castle light weight api encryption for j2me - Given final block not properly padded - encryption

Question

i have used sha256 for secret key generation and took first 16 digit for AES 128 encryption. i am getting correct encrypted and decrypted data when it is 16 or below 16 string. if it is above 16 char string i am getting 16 char with some unwanted characters. (Eg: abcdefghijklmnop5#�D�!�&M�\~C��) can anybody help me to sort this issue. please see below for code.
i have encrypted using j2me code and tried to decrypt using the given online aes crypto site (http://aesencryption.net/). i guess it is having some padding issue but i am not able to figure it out.
public static String getSHA256(String key) {
SHA256Digest digester = new SHA256Digest();
byte[] retValue = new byte[digester.getDigestSize()];
digester.update(key.getBytes(), 0, key.length());
digester.doFinal(retValue,0);
byteToStr = new String(Hex.encode(retValue));
System.out.println("byteToStr === " + byteToStr);
byteToStr = byteToStr.substring(0, 16);
System.out.println("byteToStr after subString === " + byteToStr);
return byteToStr;
}
public static byte[] cipherData(BufferedBlockCipher cipher, byte[] data)
throws Exception {
int minSize = cipher.getOutputSize(data.length);
System.out.println("min Size = "+minSize);
byte[] outBuf = new byte[minSize];
int length1 = cipher.processBytes(data, 0, data.length, outBuf, 0);
int length2 = cipher.doFinal(outBuf, length1);
System.out.println("length1 = "+length1 +"/ length2 = "+length2);
int actualLength = length1 + length2;
System.out.println("actualLength = "+actualLength);
byte[] result = new byte[actualLength];
System.arraycopy(outBuf, 0, result, 0, result.length);
return result;
}
public static byte[] decrypt(byte[] cipher, byte[] key/* , byte[] iv */)
throws Exception {
/*
* PaddedBufferedBlockCipher aes = new PaddedBufferedBlockCipher( new
* CBCBlockCipher(new AESEngine())); CipherParameters ivAndKey = new
* ParametersWithIV(new KeyParameter(key), iv); aes.init(false,
* ivAndKey); return cipherData(aes, cipher);
*/
BufferedBlockCipher decryptCipher = new PaddedBufferedBlockCipher(
new CBCBlockCipher(new AESEngine()));
KeyParameter keyDecrypt = new KeyParameter(key);
decryptCipher.init(false, keyDecrypt);
return cipherData(decryptCipher, cipher);
}
public static byte[] encrypt(byte[] plain, byte[] key/* , byte[] iv */)
throws Exception {
/*
* PaddedBufferedBlockCipher aes = new PaddedBufferedBlockCipher( new
* CBCBlockCipher(new AESEngine())); CipherParameters ivAndKey = new
* ParametersWithIV(new KeyParameter(key), iv);
*/
BufferedBlockCipher encryptCipher = new PaddedBufferedBlockCipher(
new CBCBlockCipher(new AESEngine()));
KeyParameter keyEncrypt = new KeyParameter(key);
encryptCipher.init(true, keyEncrypt);
return cipherData(encryptCipher, plain);
}
public static String encryptMe(String plain) {
byte[] plainStr = plain.getBytes();
byte[] keyStr = getSHA256(key).getBytes();
// byte[] ivStr = iv.getBytes();//
System.out.println("key str = "+Strings.fromByteArray(keyStr));
try {
byte[] encBytes = encrypt(plainStr, keyStr/*
* , ivStr
*/);
strEncResult= Base64.toBase64String(encBytes);
//byte[] encbase = Base64.encode(encBytes);
//strEncResult = new String(encbase,"ISO-8859-1");
} catch (Exception e) {
e.printStackTrace();
}
return strEncResult;
}
public static String decryptMe(String cipherText) {
try {
byte[] dcrByte = Base64.decode(cipherText);
byte[] dec = decrypt(dcrByte, getSHA256(key).getBytes()/*
* ,iv.getBytes
* ()
*/);
strDcrResult = Strings.fromByteArray(dec);
//strDcrResult = new String(dec,"ISO-8859-1");
} catch (Exception e) {
e.printStackTrace();
}
return strDcrResult;
}