Imagining for a moment that you even could get it to work...
Let's assume that the "passkey" is exclusively made up of alphanumerics? (no punctuation, and no non-printable characters).
There are 26 letters in the english alphabet in two different cases (upper and lower) for a total of 52 alphabetics. Ad in another 10 numerics and you're looking at 62 possibilities for each of the 24 positions.
6224 = 1.04 X 1043
Let's say you can get 30 GHash/s out of your cube.
1.04 X 1043 possibilities / 3.0 X 1010 hash/sec = 7.43 X 1032 sec to try all possibilities.
That's about 23571733000000000000000000 years to get through all the possibilities. (about 2.4 X 1025)
The age of the solar system is estimated to be only 4.6 X 109 years, so that's more than 5000000000000000 times more than how long the solar system has existed.
To have even a 0.01% chance of success you'll need to run the cube for more than 2357173300000000000000 years.
True, but the clue states 3 "words". This COULD mean any word, but the game is US built and has a Russian undertone (where this "puzzle" was found). So you could use dictionaries or rainbow tables to narrow down the combinations, correct? Plus your max word length would be 22 letters.