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A simple encryption scheme

Basically this scheme uses variable offsets, but it generates the bytes on the fly. They aren't truly random, but there aren't any obvious patterns and the output passes all the NIST tests.

Since a simple password can be used to do the de/encryption it is much easier to hand off to the recipient and any good password generator can create one.

Since only part of the generated sub keys are used, it becomes very difficult if not impossible to reverse engineer the sub key to find the previous or next sub key.

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Make a given number odd or even

There are times when you need to make sure your counter starts at an odd or even number.

Even is pretty simple - counter = counter + modulus(counter). If counter is even it stays, if it's odd it gets incremented by 1.

Odd is a bit more complicated - counter = counter + modulus(counter + 1), If counter is odd it stays, if it's even it gets incremented by 1.

if you're in danger of counter being the max value you can always subtract instead.

These basic algorithms should work for any language that has a modulus operator/function.

I've included a simple example in C#.