I'm not too convinced about the plausible deniability here, could someone that has reviewed their tech comment on the following:

- Encryption works by blocks and do not generally hide the size of the plaintext.

- Once I get the encrypted material, I thus approximatively know the size of the original file within a few bytes (uncertainty is due to padding to block size).

- I collect a few candidates files with size in the right range (There might be only one but it's still deniable).

Knowing your login information and the algorithm used to "derive the key from the login information", can't I encrypt the candidate and test against the encrypted material ?