Typo in Madness’ “A book on classical cryptography”?

[Shinglington]

Also, in the Cadenus example encryption. The final encryption seems to have used a slightly different last few letters of the plaintext (I get “WHATEVV” as the last bit, instead of “WUTEVUH”.
Is this an intentional “error”? Or if it’s a genuine mistake, maybe should be corrected

[Shinglington]

I’m not sure where to ask about this, but as I’m going through all the transposition ciphers in Madness’ Book on Classical Cryptography (which I wish I had found out about at the start of the challenge, but that’s my bad for not looking hard enough for resources), under the Cadenus hill climbing attack, one of the key modifications is to “change one member of the child shift key to a random number in 0, …, 25”.

I might be wrong, but should it be “random number in 0, …, 24” since cadenus “alphabet” has 25 letters which means a shift of 25 is the same as shift of 0?

Sorry if this is the wrong place to report this, but not sure how to contact Madness about it directly. (sorry if there were clear contact details that I missed)

Please let me know if I’m mistaken here.

[madness]

Thanks. Both now fixed in the github version. Harry should update his copy.

“(which I wish I had found out about at the start of the challenge, but that’s my bad for not looking hard enough for resources)”
Preparation is the key to success.

[madness]

@Harry should also update his copy of Gaines. Please. The children deserve better.

[I did try, but WordPress won’t allow us to upload the nice epub version you provided, Madness. I tried converting that to PDF, but it came out as bad as the current version. I considered linking to a  hosted copy elsewhere but haven’t had time to sort that out, sorry. Harry]

[madness]

[Thanks Madness! Uploaded the new version. Best wishes, Harry]

[Mariya07]

thanks

[HeirToTheSpare]

Hey @madness (hopefully you still see this although the cipher challenge isn’t currently active)

Going through your book now – currently on Unit 9 (Tetragram Frequency), but I’m a bit stumped, and I wondered if you could explain what you meant here in a bit more detail?

I half-understood this equation [F= ∑_tetragrams f log f_English], but I don’t understand this sentence at all:
“Note that to calculate this, we do not have to find the frequencies of every tetragram in the piece of text; instead, we merely perform the sum over the text with a one in place of f and later divide by the number of terms in the sum. ”

I thought that the equation meant you ARE in fact going through every single occuring tetragram (e.g. XXXX) in a piece of text, and adding together the number of times XXXX occurs by the logarithm of the corresponding XXXX counts taken from my corpus

Could you provide a further breakdown of what to do?

Thank you!

HtsS

(PS. Your book is a godsend)

[Author]

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