I'm fine with made-up technology and technobabble, but Digital Fortress had one thing that didn't make any sense: the supposed reason the new encryption scheme

I'm fine with made-up technology and technobabble, but Digital Fortress had one thing that didn't make any sense: the supposed reason the new encryption scheme couldn't be cracked was "rotating cleartext" - that somehow the encrypted contents could magically change over time and the brute force cracking would have to start over.