The discussion of "compress and then encrypt, or vice-versa" led me to ponder the following question: many compression containers, like
rar support encrypting these containers. For example, when creating a
7z file in 7-Zip, the program lets you enter an encryption password.
For these file types, are the files compressed and then encrypted, as recommended in the aforementioned question, or the reverse? Or, is there some way that these can compress and encrypt the data at the same time?
When I create an encrypted 7z file, I can view the filenames inside of the encrypted archive, but I cannot view the contents of those files without entering the passphrase. How is this possible? As an aside, is there any way to encrypt a 7z or similar archive such that the file names and directory structure within are not visible without using the passphrase?
I would prefer answers with definitive sources/references, not just speculation. We can all make guesses about this, but if somebody can show me documentation proving that it works one way or another, that would be ideal.