Question

My recent turn-on is using BinaryFormatter instead of some database product. I have an idea to write simple 64bit number into hardware dongle, and encrypt my files with it – via simple XOR operation. Just so it can’t be readable at some other end. Do I derive from Stream, or what?

I know I can simply put that number into the file and check against it on reading, but… I’ll feel better if it’s XORed all the way.

Answer 1

I’m not going to comment on XOR encryption, that’s too silly. Lets focus on practical guidance to implement your custom stream. You should derive it from Stream so it has a familiar interface to the user. Right-click “Stream”, Implement Abstract Class. You can leave most of the NotImplementedException throws in place, streams are commonly crippled like this. Add a private FileStream member, it will do the hard work. Then add:

• A contructor that takes a string argument, the path to the file. Construct the FileStream with it.
• Implement CanWrite, return true.
• Implement the Write() method. Do whatever you need to do to the byte[] that the client passed. You typically need your own byte[] buffer, call Flush() if it is getting too large. Or FileStream.Write() directly if you don’t need a buffer.
• Implement the Flush method. Call FileStream.Write() for your buffer, then its Flush().
• Implement Close and Dispose(), call the corresponding FileStream method.