Why we pivoted then
F2.4, the one item reopened in F2, is closed. F4 and F10 come next in the ranking but have no open item, so the next family with work is F11 (eighth), with F11.5, the poem code as SOE agents used it. The ranking is unchanged.
What happened before
- 0205: SOE's Dutch section padded each message with random letters at both ends. Padding at the end moves nothing and padding at the start moves the known words along the copper; with a repeating key or a key that slides by a fixed step, nothing fits below length 26 for any start run 0-12, on K4 as on its scrambled copies.
The change we believe is needed
- F11.5: five words picked anywhere in a remembered text, twice, as the two keys of a double transposition, then the table. First decide whether the known letters can decide it at all, and at what cost, before writing any search.