I know how. It depends on what you have encrypted. If you don't know the encryption scheme then you've got some work ahead of you. Take the ceaser cypher for instance, to reverse the working of that, you simply do something like this:
public String shiftBack(String text)
long convert = 0;
String finalResult = "";
for (int i=0; i<text.length(); i++)
convert = (long)text.charAt(i) -3;
finalResult += (char)convert;
Of course if your trying to break some ecryption, the work is beyond the scope of me.
If it's for a well known program, chances are you will need to do some research on how to break it. My guess is that it's got some kind of 128 bit encryption scheme going, and the work for that would be HAAARRRDDD.
Good luck if the file was encrypted usign unlimited strenght encryption, which is available for java (if you live in the usa). You just have to download it seperately. Do you know what encryptions scheme was used? Because if the file was hashed then there is no way to retrieve it, except for brute force attack which will take days...weeks...years!!! (depending on the length), days for anything within 5-7 characters, good luck on anything longer! And if you are building a brute force method you definatly do not want to do it in java as it is too slow, use c++ as it is much faster
hey all and thaanx for the replys, but by the sound of it, its going too be way too hard to do and take too much time... so im gonna forget it :( sadly, but maybe later on i will try again when java speeds up abit lol :)