Couldn’t you use HMAC with shared secret key to authenticate messages while keeping plausible deniability? Since the key is only supposed to be known to the 2 parties, the recipient can deduce that a message was actually sent by the sender if he did not create it himself. I think that’s what OTR was using.

DroidFS can open existing volumes. Just click on the “+” button in the bottom right corner, then on the folder icon, and then select the volume directory.

To type with only one finger, there’s 8Vim.