Re: Seriation

On Mon, 3 Feb 2025 10:17:24 +0000, Richard Heathfield wrote:

#define UPPER "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
#define LOWER "abcdefghijklmnopqrstuvwxyz"
#define DIGIT "0123456789"
#define PUNCT "!\"$%^&*()_-+={}[]#~'@;:/?.>,<\|"
 
which isn't particularly wide, but any encryption of any of those
characters will *always* produce a character drawn from the same set.
When faced with something *not* from that set, SCOS leaves it unchanged.
So I think I'm right in saying that by the above definition SCOS /is/
closed.

Yes, as I recall, and as a rather sloppy adversary unaware of your
implementation, my character set ran from char(33) ! to char(126) ~. I
think it was the gap between char(95) _ and char(97) a which caused me the
most trouble. char(96) is top left on a QWERTY keyboard. I never use it,
but it gets used as an apostrophe in some text on the web. As a result
some of my checks failed to do what I expected and I didn't feel confident
posting SCOS-based ciphers.

Happy days though.
--
David Entwistle