You're still discussing Fontana's motivations, but I see no signs that you read his book.
If you had read my blog in its entirety (and the comments I posted earlier in this thread), you would see that I pointed out that Fontana WROTE A BOOK on memory systems (mnemonics), and on ciphers, using his deliberately-mnemonic cipher.
Instead of all this speculation about his motivations, all you have to do is read his book, which I cited in my blog with a couple of diagrams as examples (Secretum BNF NAL 635).
I should think that an entire book that combines the topics of mnemonics and ciphers counts as motivation and explanation from him for developing and demonstrating his cipher.
Except for the contents and some of the section titles, the entire 150-page book is in cipher. In addition to being mnemonic in overall design, I noticed as I was reading it that he keeps abbreviations to a minimum even though they were copiously used in the 15th century. This, in addition to the mnemonics, suggests that the text was meant to be readable for anyone who has worked out (or been briefed on) the mnemonics.
To put it another way... he demonstrated that if you create the cipher using a mnemonic system you can comfortably write and read an entire book written with that cipher.
If you had read my blog in its entirety (and the comments I posted earlier in this thread), you would see that I pointed out that Fontana WROTE A BOOK on memory systems (mnemonics), and on ciphers, using his deliberately-mnemonic cipher.
Instead of all this speculation about his motivations, all you have to do is read his book, which I cited in my blog with a couple of diagrams as examples (Secretum BNF NAL 635).
I should think that an entire book that combines the topics of mnemonics and ciphers counts as motivation and explanation from him for developing and demonstrating his cipher.
Except for the contents and some of the section titles, the entire 150-page book is in cipher. In addition to being mnemonic in overall design, I noticed as I was reading it that he keeps abbreviations to a minimum even though they were copiously used in the 15th century. This, in addition to the mnemonics, suggests that the text was meant to be readable for anyone who has worked out (or been briefed on) the mnemonics.
To put it another way... he demonstrated that if you create the cipher using a mnemonic system you can comfortably write and read an entire book written with that cipher.