My code instead uses a different library written by myself for the LBC project.
In your code how many keys can you generate per minute?
About 16.7 MKeys/s, 1 GKeys/min.
Let's say 2^24 Keys/s.
To compute 2 lists of 2^28 keys, it takes 2 * 2^4 seconds, about 30 seconds. That is the time it took to retrieve the key #57.