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I don't quite get frequency analysis..

I see percentages and else, when I tried to do a frequency analysis on a pictogram cipher, the only letter I was able to analyze was the letter A.

Any step-by-step tutorial on this?

I did count, but why are there decimal numbers for certain frequencies? enter image description here

Like this picture, downloaded from the Wikipedia page.

Do mathematics have anything to do in this, such as dividing?

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Any course material or book with a title like introduction to cryptography (or similar) will address this topic and provide examples. Alternatives are: Frequency analysis and substitution cipher.

The basic steps are:

  • Decide on what you want to count: Usually first you look at single symbols first. And then bigrams. But there are other possibilities (bascially any pattern you can imagine)
  • Count the appearances
  • Put them into relation of the possible maximum count. That's a frequency.

The expression "pictogram cipher" doesn't say anything about the actual encryption mechanism. Using arbitrary symbols or pictures instead of numbers is just a form of encoding, and pretty much irrelevant, as long as you can distinguish them somehow.

However, in general we assume that it is known what kind of cipher we have. And based on that, there are different ways to do frequency analysis. Under the tag you can find a lot of questions to this topic. For example Possible ways to crack simple hand ciphers might be interesting to read.

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