I'm glad you found my optimizations to be helpful. As for the encryption, go for it, although keep in mind the age old encryption adage: The third party is always a step ahead.
For example, under the circumstances that your program was somehow compressed and uneditable, there would still be a way around it by writing a program to run through all of the keys of the calculator as seeds for rand, and then dividing those results by the rand result. The program would then check to see if the results matched, and if they did, the encryption would be broken.
They would have the rand result which the list is divided by, so all they have to do is multiply list pass by the rand result which resulted in a match.
Although one could make the point that one would first have to know the algorithm you were using to encrypt your list via rand, it is also important to remember that if your algorithm is only successful as long as the algorithm itself remains confidential, then the entire system will be made as weak as if the algorithm was public, which is actually advised in order to avoid the installation of a weak algorithm. For instance, had you not posted the mechanism of your system, I would not have pointed out this flaw, and say we were actually talking about extremely confidential and important information that needed to be encrypted, and you had used this algorithm, then the hacker would have been able to get in and access anything that you had encrypted with that particular algorithm, and maybe even more. Of course, all of this is for the sake of discussion, because most people are not well versed in cryptology/cryptography and hacking, and most likely you do not have exceedingly important information on your calculator, and anyway they could still just edit it. So, in terms of "real-world" algorithms, your encryption method could be fatal, but in terms of TI-BASIC, great job. That's one of the coolest TI-BASIC encryption algorithms I've seen. So like I said, go for it.