Why we pivoted then
F11.1-F11.4 are closed. F8 is ninth in the ranking, after F11; the ranking is unchanged.
What happened before
- 0189: the US Army's M-94 cylinder with its 25 published discs in any order, any cipher row and any group start: no setting fits K4 or its copies.
- 0190: the SOE poem code with runs of K1-K3 and Morse words as the key: as on the copies.
- 0191: the CIA's 1970s key box, with K1-K3 and Carter's book written into a box and read by columns: no setting fits.
- 0192: Friedman's keyed alphabet box on every dictionary word: no setting fits.
- Blocked: the Jefferson wheel and M-138-A strips (their alphabets are not to hand); free word picks and free tables (too many to list).
The change we believe is needed
- F8.1 next: Hill with an unknown letter numbering. Counting first: 2x2 gives 22 equations (about 103 bits) against about 96-98 bits of unknowns, so a 5-7 bit surplus and an exact test is possible. 3x3 is 21-32 bits short, so it is blocked with that number.
- After F8, F5 (Gromark: F5.2), then F9.