The block subsidy halves every 210,000 blocks. Where could this number reasonably have come from? I'm not talking about the idea of a four year interval. 210,000 is quite close to four years given 10-minute blocks - let's just assume that's the ballpark Satoshi was after.
The most obvious problem is that 2,016 (the retargeting block interval) isn't a factor of 210,000. This puts the block subsidy halving and retargeting intervals out of sync.
For example, the subsidy halving interval might have been set at 209,664 blocks. At 10 minutes/block, this would have put the halving interval at very close to 4 years (~3.99).
Granted, retargeting and subsidy halving don't appear to be related. Nevertheless, it seems awkward to create unsynchronized adjustment events.
- Was Satoshi just trying to keep things simple by choosing 210,000, or is there something I'm missing?
- What attacks might be feasible under a synchronized halving schedule that wouldn't be possible under the existing one?