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Comment by rocqua | Hacker News Reader

The hard part is generally figuring out what cipher is being used. Once you know that, and the cipher is old, modern crypt analysis would probably easily crack it.

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.

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> 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.

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.

As I recall one of the benefits of spoken Navajo was the difficulty of distinguishing it from a bad radio signal of some other language.

It had a lot of advantages. A big one being the extremely small number of people who spoke it and who lived exclusively in North America.

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.

It also was not a written language, until more recent times, therefor there was virtually no literary base for a code breaker to draw from.

http://www.lapahie.com/Dine_Bizaad_Right_Btfm.cfm

Sorta, but it’s not as though there were tons of options for affordable, near-realtime communications then.

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.

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