TheCodeBreakers
third digit, 3, and then ran along that line in the table, taking his other
keydigits from the production figures for Belgium, France, Great Britain,
and so on for 1931 and succeeding years: 134, 534, 517, and so on.
These digits he wrote beneath the checkerboard encipherment and added
them with noncarrying addition to produce the cipher:
checkerboard 91983431094110066948319910127 "plain" key
31345345171831281196110418847
cipher 22228776165941247033429328964
The encipherer divided this into groups of five, 22228 77616 59412
47033 42932 8964, with perhaps a 0 at the end to fill out the group. He
then composed an indicator group to tell the decipherer where to find the
key: 11 for the row, 3 for the column, 71 for the page (hundreds figures
were omitted; presumably the decipherer would have to try page 71 or
271 if page 171's key did not make sense). To conceal this indicator
group, 11371, the encipherer added to it, by noncarrying addition, the
annaabi.ee 
