Since "discovering" of the alphabet and writing people have tried to conseal sensitive information from the prying eyes. In XX century technical progress moved forward enourmously leaving no chance to the old, manual methods of encryption. Even now, speed of the computers doubles every year and a half forcing developers to find more and more sophisticated methods of encryption. Now we can't speak of the absolutely secure algorithms, we can just assume that the cost of breaking the system will be higher than the cost of the data consealed.

However there's one mathematically proven unbreakable method of encryption - so called One-Time Pad. It is said that a communication line between Kremlin and White House is (or was?) protected by OTP. It uses a key, which lenght is equal to the message length, so, knowing a part of it wouldn't help much supposing you have a cryptographically strong key and never use the same key twice otherwise it will be broken in a split of a second. Well, you might ask if there's such a method out there, why it is not being widely used? The answer is quite obvious - the key must be as long as a message itself and must be used only once that is more of a hindrance to general everyday use. Where to keep the key if you use it to protect files on a local computer? How to exchange keys if you send files over the net? How to generate lenghty strong keys? That makes OTP a hard bargain. Yet if you use it to protect your data it would be much easier to phisically "extract" the key, for example they might torture you, why not? :-)

Here is an encryption program that utilise OTP. It is designed for Windows'98 and I will not expect it to run on Windows'95 although you may try. It assumes that you have a floppy (disk A:) with a key file named 'key.dat' (a sample key file is here). It prompts the user for a password used to calculate the offset in the key file, so it's possible to use the same key file more than once. Encryption and decryption are symmetric. There's no need to pile up complex computation since OTP totally depends on the key. Please, don't be fooled with the size of the program - it's written in pure assembly language that's why it's so small. However the speed of processing is rather low, floppies are not as fast as we want'em to be! Here you can download a source code. It is free, for more details please reffer to the GNU public licence.