Set Miller-Rabin rounds based on bitsize

[adamantike]

Number of rounds now depends on bitsize, according to FIPS 186-4. It runs for (minimum + 1) rounds.

[coveralls]

Coverage decreased (-0.6%) to 90.292% when pulling 29f7b0a on adamantike:miller-rabin-rounds into e5839ee on sybrenstuvel:master.

[sybrenstuvel]

Please refactor so that determining the number of rounds needed is in its own function, and add unittests.

It's also quite a lot of code for something that's essentially:

if bitsize >= 1536:
    return 3
if bitsize >= 1024:
    return 4
if bitsize >= 512:
    return 7
return 10

[coveralls]

Coverage increased (+0.1%) to 91.462% when pulling 85275a9 on adamantike:miller-rabin-rounds into 96eaa5e on sybrenstuvel:master.

[coveralls]

Coverage increased (+0.1%) to 91.462% when pulling 85275a9 on adamantike:miller-rabin-rounds into 96eaa5e on sybrenstuvel:master.

[adamantike]

That was my first approach, but I kind of over-thought it by trying not to add new if ...: return... blocks when adding new cases in the future. Actually, being k = 3 the current minimum, there won't be a lot new cases :P

[sybrenstuvel]

Great! Merged in 38a7255