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+--- Thread: Historical ciphers, when they were introduced and their effect (/thread-4712.html)
RE: Historical ciphers, when they were introduced and their effect - Rafal - 20-05-2025
And I'd like to add one thing. All these ciphers are not similar at all to Voynich Manuscript. The most similar way I can think of would be just coding letters as Roman numerals.
Actually I have seen such cipher, most probably older than Voynich Manuscript.
I don't remember where I have found it but have a look:
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RE: Historical ciphers, when they were introduced and their effect - ReneZ - 20-05-2025
(20-05-2025, 04:28 PM)Koen G Wrote: You are not allowed to view links. Register or Login to view.Conclusion: all known ciphers that have actually been used before the late 15th century make the plaintext even less like Voynichese than would be the case with simple substitution.
That seems largely correct to me.
Let's also not forget that this text has primarily attracted cryptographers and cryptologists, right from the very start. This is therefore perhaps the most trodden area of all. Unfortunately, we don't seem to have any detailed explanations of all the things that have been studied, and why they failed...
RE: Historical ciphers, when they were introduced and their effect - MarcoP - 21-05-2025
(20-05-2025, 10:28 PM)Rafal Wrote: You are not allowed to view links. Register or Login to view.And I'd like to add one thing. All these ciphers are not similar at all to Voynich Manuscript. The most similar way I can think of would be just coding letters as Roman numerals.
Actually I have seen such cipher, most probably older than Voynich Manuscript.
I don't remember where I have found it but have a look:
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The text is transcribed here: You are not allowed to view links. Register or Login to view.
Bede is describing the Greek system to encode numbers. They use all the alphabet to represent numbers (rather than only a few letters, as the Roman system). Bede discusses a system to represent numbers with finger gestures. If one knows both the gesture system and the Greek numbering system, they automatically also have a way to encode the whole alphabet with fingers. So this is about encoding a text with gestures, not a verbose cipher where Greek letters are written by longer Roman numbers.
RE: Historical ciphers, when they were introduced and their effect - Mark Knowles - 21-05-2025
The 1424 Milanese cipher that I referred to uses roman numeral encoding for some substitutions. I have not seen this in later Milanese ciphers, but then that period appears to be a very dynamic time in Milanese cryptography.
RE: Historical ciphers, when they were introduced and their effect - Rafal - 21-05-2025
Thank you for the explanation and the link, Marco. I have always wanted to read that text
So it's both about Greek way of writing numbers and so called monastic sign languages:
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Yet I would say that it's not completely useless for Voynich Manuscript. It shows that people in medieval ages were conscious about different numeric systems. In Roman numerals only few letters are used like I, V, X, L, C, D, M. But in other systems (Greek, Hebrew, Slavonic) every letter is used and every letter means some number.
So if letters may mean numbers then numbers may mean letters, right?
And you can code letters with numbers. And Voynich vords are similar to Roman numbers.Today a lot of ciphers use numbers and such numeric ciphers appeared already in the 1500s. See the great website Cryptiana for such stuff ( You are not allowed to view links. Register or Login to view. )
But in the 1400s there were no numeric ciphers or almost no numeric ciphers. They became a standard when Arabic numbers became a standard. Voynich Manuscript seems out of place here, like someone was coding words with some mutated Roman numerals.
RE: Historical ciphers, when they were introduced and their effect - Mark Knowles - 21-05-2025
(21-05-2025, 12:39 PM)Rafal Wrote: You are not allowed to view links. Register or Login to view.Thank you for the explanation and the link, Marco. I have always wanted to read that text
So it's both about Greek way of writing numbers and so called monastic sign languages:
You are not allowed to view links. Register or Login to view.
You are not allowed to view links. Register or Login to view.
Yet I would say that it's not completely useless for Voynich Manuscript. It shows that people in medieval ages were conscious about different numeric systems. In Roman numerals only few letters are used like I, V, X, L, C, D, M. But in other systems (Greek, Hebrew, Slavonic) every letter is used and every letter means some number.
So if letters may mean numbers then numbers may mean letters, right?
Today a lot of ciphers use numbers and such numeric ciphers appeared already in the 1500s. See the great website Cryptiana for such stuff ( You are not allowed to view links. Register or Login to view. )
But in the 1400s there were no numeric ciphers or almost no numeric ciphers. They became a standard when Arabic numbers became a standard. Voynich Manuscript seems out of place here, like someone was coding words with some mutated Roman numerals.
Arabic numerals were used as symbols in 15th century ciphers. I don't think it was the adoption of Arabic numerals more widely that explain the increased use of numbers within ciphers. There was a natural shift over time from elaborate invented symbols in ciphers, e.g. in Paolo Guinigi's cipher ledger, to the more straightforward, simple and logical use of numbers.
It is a interesting question as to whether the style of symbols used in the Voynich manuscript can be used to date it.
RE: Historical ciphers, when they were introduced and their effect - R. Sale - 21-05-2025
If the trickery in the VMs illustrations includes everything from code shifts to heraldic canting, to intentional dualism, why should the language be any less? In the early 1400's, if the VMs language is rational, the author is a savant. If the language is not translatable, nothing has changed.
The three interpretive systems overlaid on the 4 x 17 symbol sequence (f57v) are an opening to further investigation. They show at least an acquaintance with Greek. There are three glyphs between lambda and omicron. The presence of proper structure is an objective demonstration of identity. And likewise, for the medieval and Latin numeral interpretations.
Perhaps there is a way to reconstruct something like a Polybius' square. The sixth symbol is a quincunx.
RE: Historical ciphers, when they were introduced and their effect - kckluge - 21-05-2025
(20-05-2025, 02:13 PM)Koen G Wrote: You are not allowed to view links. Register or Login to view.2) Introduce nulls.
--> even LESS like Voynichese
- Some extra characters in the ciphertext don't correspond to anything. This can be used to obscure the most frequent characters, break up common bigrams etc.
- Existed before the 15th century (?)
- Effects: larger glyph set, increased entropy (sometimes or always?)
3) Homophonic cipher
--> even LESS like Voynichese
- Each plaintext letter can be replaced by multiple ciphertext symbols. Hides frequency -> harder to crack
- Existed before the 15th century (?)
- Effects: larger glyph set; I would expect higher entropy but I'm not sure.
In the case of nulls entropy can at least *potentially* decrease (consider the reductio ad absurdum case where 99% of the text is a single null character, although the Copiale may well be a real world example).
In the case of homophones, I believe the following is a correct proof that the 1st order entropy must be higher than that of the underlying text:
* Consider the contribution of letter 'x' to the entropy, p(x) * -log(p(x))
* Without loss of generality, represent 'x' in the cipher with two homophones 'y' and 'z', so p(y) + p(z) = p(x) --> p(y) = p(x) - p(z)
* For p(x) > p(z) > 0, -log(p(z)) and -log(p(x) - p(z)) > -log(p(x))
* -log(p(z)) > -log(p(x)) --> p(z) * -log(p(z)) > p(z) * -log(p(x))
* -log(p(x) - p(z)) > -log(p(x)) --> (p(x) - p(z)) * -log(p(x) - p(z)) > (p(x) - p(z)) * -log(p(x))
* --> (p(x) - p(z)) * -log(p(x) - p(z)) + p(z) * -log(p(z)) > (p(x) - p(z)) * -log(p(x)) + p(z) * -log(p(x))
* --> (p(x) - p(z)) * -log(p(x) - p(z)) + p(z) * -log(p(z)) > p(x) * -log(p(x))
I'm pretty sure that proof should generalize to the unconditional 2nd order entropy, but I'd have to think longer and harder than I'm prepared to do at the moment to see if there's a proof that the conditional 2nd order entropy must also be larger...
RE: Historical ciphers, when they were introduced and their effect - kckluge - 21-05-2025
(20-05-2025, 04:28 PM)Koen G Wrote: You are not allowed to view links. Register or Login to view.Conclusion: all known ciphers that have actually been used before the late 15th century make the plaintext even less like Voynichese than would be the case with simple substitution. Any proposed cipher methods that do produce Voynichese-like properties are therefore hypothetical.
Or at the very least anachronistic.
There is undoubtedly utility (if only for the benefit of relative newcomers) to going through how the Voynich text doesn't look like what you get if you apply known varieties of early 15th century ciphers to a natural language, but in some sense (if the text is an enciphered natural language) I think that's looking at the question backwards. If the text is an enciphered natural language, then the text has to be engaged with on its own terms, no matter how anachronistic the result of doing that may be. I think an approach more along the lines of William Friedman's "Synoptic Tables for the Solution of Ciphers" (You are not allowed to view links. Register or Login to view.) is more likely to be productive, i.e. how do the properties of the text constrain what type of cipher (if any) we could be looking at? At some point going down that road gets you to "not like anything we know was in use in the early 15th century (at least in Western Europe)" as a side effect of the analysis.
RE: Historical ciphers, when they were introduced and their effect - Koen G - 21-05-2025
Just for clarity, I didn't mean hypothetical in a dismissive way. Plenty of ciphers are probably the only attestation of their exact method. But it's still interesting to note that, if it is a cipher, it swims against the tide.