Linux – How to hide a code from theself until a specified time

Essentially, what I need is some way to generate and store a random string (20 characters long, say) for some period of time, such that there is no way for me to recover the string until the end of that period. I am running standard Ubuntu 12.10.

Things that make this hard:

• I have root access.
• The computer might shut down and start up during the period.
• There needs to be no way for me to recover the string before the period ends.
• I'll have no internet access for the duration of the period.

The reason I need to do this is that I have an addiction to internet porn. Most of the time I can control it, but I get cravings late at night. This is even harder because I use a computer for my work and I work from home. So lately I've started removing /sbin/dhclient, which disables internet connectivity (until I can get a liveCD and copy the file back, but that takes a while). What I want to do instead is to generate a password for dhclient (by encrypting dhclient, or just creating a zipfile with that password), and then only have the password given back to me the next morning. Basically I'm trying to find a commitment device, a bit like an alcoholic pouring his liquor into the sink.

Some possible avenues of attack:

• Run a program that generates the string and stores it in memory, waits for n seconds, then prints the string. This won't work because the process would be killed if the computer restarted, and I might look in the program's memory to find the string.
• Let the program change the root password to the randomly-generated string, removing root access from me; let it store the string in a file that only root has r/w access to, and let root repeatedly run a program which checks whether the period is over, and if so, give me the string (and thus root access). This sounds like it would work, but I can get around it by changing the time in the BIOS.
• An idea I just had: write one program that removes root access and stores the password in a file that requires root to read. Then let root use cron to run a program every minute that checks for the existence of a file called "delayed_root_request". Every time it runs, if delayed_root_request exists, it increments a number stored in a "root_timer" file that only root can read/write. (If that doesn't exist, it creates it and makes it contain "0".) When the number in root_timer reaches something like 60*8=480, it gives me read access to the file that stores the root password and thus root access. So I can run a script that removes root access, stores the randomly-generated password in a root-access-only file, and breaks dhclient. When I want internet access back, I create the file "delayed_root_request" and have to wait 8 hours for the password. If at any time during those 8 hours I decide root access would just make me procrastinate, I just delete the file and I have to start the count over. If the computer restarts, the counting just pauses. I'd have to give GRUB a password (e.g. http://sourceforge.net/projects/grubpass/). I can still get in with optical media, or just taking out the hard drive, but I can make that inconvenient by deleting all copies of the Ubuntu iso file that I have, and I can give away all my liveCDs (and won't be able to make more without internet access).

There might be a really easy way to do this that I'm missing – please tell me any ideas you have.

Any help with this will really be appreciated!