Monoalphabetic cipher using different languages in the same plaintext Today I learned the principle of the monoalphabetic cipher. It's simple to decrypt a ciphertext written all in the same language (english for example) because I can use the syntactic properties as well as letters' frequency. What about writing a message using different languages in the same text? 


  Il gatto è salito sull'albero. I don't know how to bring it down! 


In this way I don't have any clues on how to decrypt the message, right? The only information that could help me should be the knowledge of which languages are in use.

Thank you very much for your time.
I don't think that this will make cracking the code that much harder. You could not use statistical "most popular letter" anymore, but I don't think that in English or Italian there are that many words that are exactly five letters and letters 3 and 4 are identical like in "gatto". We could also check what four and three letter words that share the same final two letters sometimes appear next to each other like in "know how".

And what if someone knows that the message is about a cat? He just has to check for that word in two languages, and he will get three (or in this case four) bits of the key.