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Re: Cryptanalysis in QST
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That really sounds like a Playfair variant. Each party must have the key word(s) to encrypt and decrypt the message. Operationally that could boil down to each party having the same book available and sent the page/line/word numbers in the message header.
On Tue, Dec 10, 2019, 17:23 n5ib_2 <n5ib@...> wrote:
That is the "book code" or "poem code" that later, due to the efforts of Leo Marks (See "Between Silk and Cyanide") became the WOK (Worked Out Keys)