Encrypted files in an encrypted partition or folder
In short: does storing these encrypted files in an encrypted partition/folder create the same potential weaknesses as cascade encryption? If not, what of encrypting a .tar of encrypted documents?


An encrypted file inside an encrypted container is a cascade of ciphers, almost by definition.

Is that a problem? Not really. A cascade of ciphers shouldn't be weaker than a single layer of encryption, unless something is wrong – e.g. the keys are not independent.

Concerns about cascades are mostly theoretical – I wouldn't expect the cascade to ever be weaker when you have two different ciphers. There is no easy way to prove that for real world ciphers, however, and there's always the risk of sidechannel attacks and bugs, so it isn't something to recommend as a way to strengthen a system.

In your case it's still the best thing to do, since you don't want all those files to be visible decrypted when the filesystem is mounted.