A known mistery
> First, and contrary to what ABC says, this code is not very sophisticated. It is a monoalphabetic substitution system with homophones to which a set of terms of agreed language has been added. I have a handful of Spanish codes of the time and I can assure you that there are more sophisticated codes than this one. For example, the so-called Clave de los Capitulaciones is similar in form and structure, being at least ten years older; and the General Figure of the Catholic Kings, dated similar to that of the Great Captain, had no less than 670 terms in agreed language.
> Third, these types of keys were already vulnerable to cryptanalytic attacks at that time. Manias such as encrypting only part of the letter, or repeating the used encrypted terms, made them relatively easy to decipher by unauthorized users.
There's also a pictures of what the deciphered key looks like both in the 1800s version on old paper and the CNI's version on graph paper which is interesting.
2018 = http://elprofedefisica.naukas.com/files/2018/02/Clave-Gran-C...
Interestingly, to break the code he relied on a code-breaking manual written by one of his own ancestors, Cicco Simonetta ! When I first learned about this, I thought it was incredibly silly that he didn't ask a modern cryptographer for help. But in some ways, Cicco's manual, written around the same time, is more useful: it focuses on precisely the kind of codes that would have been used for the letter, and the techniques it describes are reasonably effective (essentially frequency analysis, with some specific tricks for documents written in Latin or Italian). And it is certainly more narratively satisfying that he ended up breaking it on his own, following his ancestor's manual!
If you want to know more, he wrote a book on the subject:
And as another fun bit of trivia, he ended up consulting on the historical aspects of Assassin's Creed II, which takes place in Florence around the time of the Pazzi conspiracy!
On a side note, (as long as they mention Rosetta Stone) does writing in another language count as a form of cryptography? If so, it should likewise be trivial to crack any remaining unknown ancient scripts.
But I'm probably being ignorant somewhere here.
This is down to kerchoffs principle, which states that you should not rely on the secrecy of what cipher is being used, only on the secrecy of the key.
As such, writing in another language is not cryptography.
There is a name for hiding info by depending on the method being unknown: steganography.
This includes different using different languages (see the navaho code talkers), or hiding data in the less significant bits of an image, or hiding a message in the first letter of every sentence and so forth.
Since "language as cryptography" breaks Kerchoff's Principle, doesn't that just make it bad cryptography? Shouldn't that make it all the easier to use cryptanalysis to translate it?
Unrelated point: I thought Steganography was the art of hiding the _fact_ of encryption. If a Japanese analyst hears someone talking in Navajo, it's no secret that some unknown message is being conveyed.
It’s also hard to overstate how obscure Navajo was. Young and Morgan developed a writing system for it in 1937, and the first dictionary was developed as part of the war effort (and thus not publicly available) in the 1940s. The Navy estimated that ~30 non-Navajos spoke the language at the time.
It’s thus pretty unlikely that “this is Navajo” would have been an Axis analyst’s first guess—-and even if it were, there were minimal resources available. The language is pretty far from Japanese or German, which also doesn’t help.
On top of all that, the messages being sent weren’t literal Navajo—-there was sort of a substitution code that used common Navajo words to stand in for military items. The Japanese actually captured a [Navajo solider](https://en.m.wikipedia.org/wiki/Joe_Kieyoomia) but he could not undertatand the transmitted messages.
They could also have “fun” and make it very hard to crack. For example they could call a submarine a “metal fish” one day and a “sea snake” the next day and leave everybody scratching their heads. As a native speaker they could use subtle context to convey the message and that turns out to be extremely difficult for an outsider to grasp.
Modern encryption is fast and flexible but there are old ciphers that are just as strong when used correctly.
Modern cryptography is strong due to mainly a few key aspects, randomness which enables us to generate true or near true random keys, key exchange/distribution (electronic communications and various key exchange algorithms like DH) and non alphabetical plain text and keys.
However when used correctly a polyalphabetic cipher like a running key cipher does produce a One Time Pad which is effectively impossible to crack through non exhaustive means.
Supposing by poly-alphabetic cipher you mean a substitution mechanism based on multiple alphabets (https://en.wikipedia.org/wiki/Polyalphabetic_cipher) (e.g. Enigma). This class does not provide information theoretic security. OTP does - it literally defined the notion.
>> Modern cryptography is strong due to mainly a few key aspects, randomness which enables us to generate true or near true random keys, key exchange/distribution (electronic communications and various key exchange algorithms like DH) and non alphabetical plain text and keys.
Maybe I am misunderstanding the statement you want to make here, but modern cryptography is strong because it is based on i) notion of information theoretic security ii) notion of computational security. The latter, upon which e.g. the Diffie-Hellman key exchange or RSA are built, states that distinguishing the output of the function from a particular distribution, can be used to solve problems we consider intractable (either on average or in the worst case).
I am not sure to what you are referring to when stating:
>> Modern encryption is fast and flexible but there are old ciphers that are just as strong when used correctly.
To my knowledge that is not correct, but I am curious. (Shannon's analysis was the first rigorous treatment and bootstrapped the field.)
Modern cryptoanalysis still requires large corpus' of data to work through.
For an example of the work it takes to break classical cipher methods, consider the Kryptos sculpture (its a sculpture at the CIA headquarters with 4 enciphered texts on it).
It was unveiled in 1990. The forth puzzle is still unsolved.
I think this is the key I was missing. Like, it's a catastrophe if something is degraded to RC4, but we can't break something from 500 years ago. But I guess for modern communications you automatically get a very large corpus if you just wait for a little bit.
>it should likewise be trivial to crack any remaining unknown ancient scripts
That doesn't follow. Part of successfully decrypting a message is knowing when you have the right answer. That doesn't apply if you're looking at a limited dataset (or claytablet set), and you have no idea about the context the texts were written in.
It also wasn’t just haphazardly deployed like a DIY crypto system inside some app might be. There were tests and working groups and stuff like that.
And do not forget the Voynich manuscript , from the 15th century, which still remains un-decyphered.
Strongly recommend this textbook https://www.amazon.com/Story-Decipherment-Egyptian-Hieroglyp...
Its all about deciphering ancient languages. It doesn't quite get as far as the very recent breakthroughs e.g. Inca knots.
 - https://en.wikipedia.org/wiki/Linear_A
Edit: Link to the actual Archives entry: http://discovery.nationalarchives.gov.uk/details/r/C12056