In regular maps the starting player gets 3 keys and second player gets 4. On subsequent turns each player gets 3 keys.
On large maps, the starting player gets 4 keys and the second player gets 6. On subsequent turns each player then gets 5 keys. The is broken for 2 reasons:
Compare it to the small map gameplay above, breaking game theory imo, and
6 key phobs are significantly more powerful than 4 key phobs, which are also materially less powerful than 5 key phobs.