If your problem is actually that “you want to focus on something important for a while,” then I think you should reconsider whether an encryption scheme is really the next logical step to solving your original problem. Elaborately tying yourself in straightjackets may just distract you further from that “important thing” you initially cared about.
(In this above XKCD comic, replace “write a program” with “devise and implement an elaborate cryptographic strategy.”)
The ideal would be to obey a self-declaration of mind over matter: “you won’t be distracted!” But that’s easier said than done.
Then there’s logic: “compulsively checking information feeds and my inbox is actually making me less happy.”
Fear is a good motivator, too. “If I don’t focus on this important thing, then I’ll dishonor myself and/or lose my job and/or disappoint my significant other… ultimately, making me unhappy.”
Supervision is another: “I’d goof off, but this other person is in the room, and will bear witness to my transgression.” Go into the office, or create/find a shared workspace. To save on automobile-related costs while still controlling myself, I like to imagine there is an invisible camera observing me at all times, and to behave accordingly (and smile for it).
Alternatively, there’s acceptance: you realize you really would be happier by throwing everything else away; the “important thing” really wasn’t important, with your soul’s protests as evidence. You do that thing now — even if, in the worst case, you are judged by others, and you lose your home and wife. However, that distraction—now not a distraction, rather your priority—makes you happier than those things/people anyway.