Yeah, I know I made Encoding and Decoding Blocks before. These are even better, and much more secure: Snap! Build Your Own Blocks Oh yeah, there even JS free. P.S. You can do multiline.
@bh you asked for this.
Yup, using bignums helps, but still only for would-be codebreakers who can't see your code. What you really want are encode/decode blocks that take a second input, the password. For example, let the password be a number from 1 to 100 instead of picking a random one.
Of course if you really want a secure cipher you have to go public-key.
Great minds think alike
I also used bignums and unicode to encrypt and decrypt. And I eventually multiply by a key and add another key to provide security. One can create the keys in various ways such as random or by converting text to more numbers.