UnresolvedFarm keys FARMING METHOD ?

Anyone know some good way to farm keys fast in zombies ?
i try changing rounds to 100+, using speed to pass rounds faster, but nothing worth , oyu get most keys if play normaly with GOD mode and AMMO , and less keys when change round to 100+ or using speed time.
anyone know some good way to farm keys ??

NO ,i think maybe related time. i play 30+ use 20min ,i have 20 key, but i play 30+ use 1h ,i have 30+ key. so maybe related time. just maybe. just maybe.
my english so bad.

I need keys as well

Keys are not based on rounds or time spent.

It's based on XP or score.

I did two runs to rounds 31. One doing the easter egg and the other using traps to speed through. The one with higher XP gain (doing the easter egg) gave me 29 keys and the other only gave me 20 keys. 9 key difference even though they both ended at Round 31.