Thread

GPT-6 Astra Solves a WWI German Radio Cipher

400 points · 180 comments · nsoonhui

FabHK · 1789812360 · focus · HN ↗
Isn't that a very simple substitution cipher (any clear text letter is substituted by two letters of cipher text, with a fixed one-to-one correspondence)? And aren't they all amenable to very simple cryptanalysis, at least if the encrypted text is long enough, by counting how often certain letters appear, and then trying to plug in reasonable guesses?
<a href="https://en.wikipedia.org/wiki/Substitution_cipher" rel="nofollow">https://en.wikipedia.org/wiki/Substitution_cipher
1. jgrahamc · 1789813332 · focus · HN ↗
  It is not a simple substitution using the polybius square with pairs of letters from ADFGVX mapping to 25 letters of the alphabet.
  The first step is to take each letter and turn it into a pair of letters from ADFGVX but the second step is then a keyed columnar transposition.
  1. FabHK · 1789840570 · focus · HN ↗
    Ah, thanks, seems that's in the second part, but not very well explained.

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