function EncryptStr(plainText,key,mode) // key should be 256 bit
{
	mode = ( (typeof optional == "undefined") ? "ECB" : mode ); // optional parameter

    var keyByteArr = hexToByteArray(key);
    var cypherByteArr = rijndaelEncrypt(plainText,keyByteArr,mode);
    var cypherText = byteArrayToHex(cypherByteArr);

    return cypherText;
}

function DecryptStr(cypherText,key,mode) // key should be 256 bit
{
	mode = ( (typeof optional == "undefined") ? "ECB" : mode ); // optional parameter

    var keyByteArr = hexToByteArray(key);
    var cypherTextByteArr = hexToByteArray(cypherText);
    var plainTextByteArr = rijndaelDecrypt(cypherTextByteArr,keyByteArr,mode);
    var plainText = byteArrayToString(plainTextByteArr);

    return plainText;
}