[Kerckhoffs's principle][1] is named after a publication over 130 years old. Yet it is still something that is commonly misunderstood and challenged by newcomers to cryptography. [This question from Open Source Stack Exchange seems typical][2], and one answer to it implies that at some point, cryptographers in general "got it" and it has become a cornerstone of modern cipher design.

This seemed interesting to me - was the principle for Kerckhoffs's original paper (originally design principle 2 from a list of 6 according to Wikipedia) broadly accepted from the moment of publishing, or has it taken time, specific events and/or the failure of many electronic designs before attaining its current importance?

I searched for "violations of Kerckhoffs's principle" and found a few modern examples (e.g. [MiFare being hacked][3]), where essentially the cipher was weak - and easily understood to be weak at the time it was made - but kept secret in the vain hope that reverse-engineering it would be too much of a challenge. However, I didn't find anything I could relate to history such as a series of "secret" ciphers failing badly in the 1990s for instance. So I'm starting to think the principle really has been well-understood ever since it was published, just not followed in practice by some institutions that should have known better had they asked any cryptanalyst. Therefore one way re-framing my question might be "Has there ever been a time in modern (computer-based) cryptographic practice where Kerckhoffs's principle was not considered as important as it is today?"

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I tried to use [Google ngrams][4] to get a sense of when terms may have become popular, and didn't notice any spiking, but a steady rise in term frequency for e.g. "security through obscurity" from 1970's to present day. Does that point to use of Kerckhoff's principle as a norm (or even just as a label), due to increased academic study of cryptography? This has been suggested in comments. Is there better evidence for that than my ad-hoc searching?

  [1]: https://en.wikipedia.org/wiki/Kerckhoffs%27s_principle
  [2]: http://opensource.stackexchange.com/questions/207/how-is-open-source-encryption-safe
  [3]: http://www.cnet.com/uk/news/d-day-for-rfid-based-transit-card-systems/
  [4]: https://books.google.com/ngrams