This script generates a binary value according to the tips of MrFreeDragon
he puts from 29 to 35 "1´s" in binary
But actually these tips are not very big help. Even if they are correct, the decrease in total number of combinations is not too much.
For example, for
64bit key the total range is
2^63, if we take only the keys with
29-35 quantity of "1"s , so the total combinations to test is
2^62.23 (total decrease of the range less than twice).
If we limit our range to exact
32 "1"s (32 "1"s and 32 "0"s), so the total amount of combinations will be
2^59.58 (decrease approx. by 10 times)