Encrypt password for oneself on paper Assume the following:

You have to encrypt a file (ZIP-file) containing import information. This file should be password-protected and you want to leave yourself the password encrypted (on paper, maybe bury it somewhere in your yard, hide it behind the walls, you name it). How could you encrypt it so that you might be able to recover it? You might as well assume extreme situations like suffering a stroke (and recovering) or becoming enemy of the state and thus being pursued by government agencies. Apart from a secure physical location (six feet under) it should also be logically secured.

Some thoughts:


tabula recta might work -> how long could passwords be (more than 24 characters?)
the information to decrypt the password should be self-containing -> hinting to things only you yourself know or something similar
or does it make no difference if I buried a flash drive somewhere?


Thank you for your thoughts on this one.

Update 2017/12/31:

I checked the key sharing schemes article on Wikipedia. Actually this is slightly beyond the scope of my question - although I like the idea of splitting the key!

I am more concerned about proper encryption. I would really like to find a way to create a proper key and encrypt a password.
Key management is always an issue, and you could write books about it.

I'd myself create two keys by splitting one off a normal symmetric key. This key I would print out on paper and store in a secure location such as a physical (fireproof) safe. I'd store the other part in another secure location, such as a bank, referring to the bank from the safe (you know where your own safe is, but will you remember the details of the bank?). To decrypt you can re-establish the key and then decrypt the password.

There are literally hundreds of other ways of accomplishing the same thing though. Which one is most secure depends on the situation and threats. In the end this is about balancing convenience and security. You can have a look at key sharing schemes to have some more ideas for splitting and securing keys. If security is a real issue you should be just using keys, no passwords - they are simply too easy to guess or too difficult to remember. 

I'd not store the keys on flash - there is too much chance of it losing too much charge. Burying anything is not a good idea at all; somebody may accidentally or purposefully find it and with the amount of trash we generate, it will not be a great archeological find far into the future - please do not bury your electronics. Besides the chance of damage is just too likely when you bury anything.