It was introduced under the name "Solitaire", "Pontifex" was used initially as a temporary code-word when characters couldn't speak freely.
I've always wondered if just using plain RC4 (adapted to a card deck) would be simpler (and probably more secure). Adding two-digit (0..52) numbers by hand is easy for almost everyone, and RC4's swap step is no more involved than the `cut` operation of Solitaire. The only downside is that it requires user to keep track of `i` and `j` - two additional two-digit numbers (in memory, because writing anything down is against the threat model of characters in the story). I agree it's error-prone. But, assuming temporarily writing things down with pen and paper is OK according to my threat model, I think RC4 would work nicely.
Of course Bruce is the world-class expert in cryptography and I'm not, so you should probably ignore my grumbling here :).
edit: To be clear I mean someone with a better understanding of cryptography than me. I don't doubt the author's expertise.
Fortunately, many major newspapers distribute keys each day.
And there are so many to chose from https://vineyardgazette.com/news/2021/09/20/bridge-column-se...
NORTH S A 6 3 H Q 2 D Q 10 8 7 4 2 C K 5 WEST EAST S 7 S J 10 9 2 H J 10 9 8 5 H K 7 6 4 3 D A J 6 3 D K 9 C J 10 8 C A 9 SOUTH S K Q 8 5 4 H A D 5 C Q 7 6 4 3 2
I made a random number generator in Automate that takes takes the end digits that are really just noise and put that into a random seed.