Engineering your own voynich

[oshfdk]

Could it be that there are different encryption rules for words in mixed case and others for all lower case, maybe even for camel case (uppercase in middle)?

This is exactly the problem with short cithertexts, anything is possible. Normally I would try to break an unknown cipher by iterating over various methods of encryption and trying to exclude them one by one as quickly as possible. So, instead of looking for ways to support a particular method, one looks for ways to prove it wrong and move on. With a long ciphertext it's quite easy to identify unrealistic or highly improbable examples in the ciphertext for most methods of encryption, until you stumble upon the right one. With a short ciphertext it's impossible to find counterexamples, so you have to perform a deep search of methods, following each of them to its logical end. This is slow and tedious, and this is what I think most authors of experiments like "let me design a cipher that looks like Voynichese and you try to break it" don't really understand. Design the cipher, ok, but do provide some 50 kilobytes of ciphertext and then we can run some meaningful statistical attacks like those we can run on Voynichese. Inventing a cipher that is virtually unbreakable from just a few lines of ciphertext is not very hard and doesn't prove any point.