Turing, DermotDesenclos, CamillePierrot, Cécile2026-06-152026-06-152026-06-221736- 6305https://hdl.handle.net/10062/122068German diplomatic signals enciphered in the Floradora double-additive system were broken at the end of 1942 as a result of Anglo-American collaboration. The American contribution was a novel and ingenious system of machine search for likely additive combinations, which allowed the choice of additives to be revealed. The paper suggests a reconstruction of the machine methodology, which used punched-card sorting and collation.enAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttps://creativecommons.org/licenses/by/4.0/Floradora cipherSuperenciphered codePunched-card machine codebreakingBletchley ParkArticle