If we’re going to talk about PRNG’s and Stream Ciphers then we need to at least mention

Block Ciphers.

I’m not saying this with the intent of making a case for block ciphering in K4.  It’s just nice to complete a general set of ideas with some vague sense of completeness.  PRNG, Stream ciphers and Block ciphers are on a different plane entirely from the old school analog methods or even the mechanical ciphering.  Despite that, there are some haunting similarities if one accepts that numeric substitution/encryption algogrithms have replaced the alphabetical systems of pencil and paper cryptography.  They are not separate entities but more products or stages of the evolution of cryptography and the later incarnations will contain a remnant of their predecessors for better or worse.

I don’t think K4 is a block cipher.  I also didn’t know what a block cipher was when I started all this so hopefully the information will prove useful to anyone who finds themselves in the same ignorance.  It will take more than a webpage with some paragraphs describing it to make me comfortable with all the ins-and-outs but I’ve read enough to be convinced that it doesn’t seem probable that K4 uses something like this.  Possible, but not probable, not probable at all.  If anyone devotes any effort to trying though, I would be interested to hear how it goes.