ENCRYPTION
Introduction
Often there has been a need to protect information from 'prying eyes'. In the electronic age, information that could otherwise benefit or educate a group or individual can also be used against such groups or individuals. Industrial espionage among highly competitive businesses often requires that extensive security measures be put into place. And, those who wish to exercise their personal freedom, outside of the oppressive nature of governments, may also wish to encrypt certain information to avoid suffering the penalties of going against the wishes of those who attempt to control.
Still, the methods of data encryption and decryption are relatively straightforward, and easily mastered. I have been doing data …show more content…

Further, if you use an 'XOR mask' in combination with this ('flipping' the bits in certain positions from 1 to 0, or 0 to 1) you end up making the code breaking process even more difficult. The best combination would also use 'pseudo random' effects, the easiest of which would involve a simple sequence like Fibonacci numbers. The sequence '1,1,2,3,5,...' is easily generated by adding the previous 2 numbers in the sequence to get the next. Doing modular arithmetic on the result (i.e. Fib. sequence mod 3 to get rotation factor) and operating on multiple byte sequences (using a prime number of bytes for rotation is usually a good guideline) will make the code breaker's job even more difficult, adding the 'pseudo-random' effect that is easily reproduced by your decryption program.
In some cases, you may want to detect whether data has been tampered with, and encrypt some kind of 'checksum' into the data stream itself. This is useful not only for authorization codes but for programs themselves. A virus that infects such a 'protected' program would no doubt neglect the encryption algorithm and authorization/checksum signature. The program could then check itself each time it loads, and thus detect the presence of file corruption. Naturally, such a method would have to be kept VERY secret, as virus programmers represent the worst of the code breakers: