[-Ramirez-]

It's easy now that you've given that much information... Well... easy to get the second one. All you need is a way to get the checksum on the first and you're set.

The second one is:
"This is a test string. No, you don't win anything. Sit back down and pay attention." ...obviously

I just figured out the first one's checksum as well. The first time through the post, I didn't even see you had given the digit length and the first 4 digits. Anyway, the checksum becomes 14259735 and gives you the string of "This is a simple text string designed to show how this encryption system operates. It pads out strings with lots of random characters based on a user-defined checksum. Isn't that fun?"

I'm not sure if you expected people to be able to create a script to figure out the checksum... as that's rather impossible, since the script won't have a clue what to look for. As for deciphering the string with the correct checksum, I made a script to do that. If you want me to post it, I will.