In reply to Rick Wicklin.

Hi Rick. Nice to hear from you. I recall a SAS manual where it is suggested that large keys are preferable. But, you are the expert, so I'll take your word for it!
Very clever idea with the key. In reality, I'd probably use AES. I though of ways to make it harder to break the cipher by using different distribution and one of several different methods of generating the series, such as you discuss in several of your papers. By the way, did you get a chance to look at my "The Enigma Terrorists" book?