Can someone explain, how the new "miners can volunteer to raise their share difficulty"-protocol change works? I don't understand how cheating is prevented.
Can't you just mine in secret and for example find a difficulty 1000 share, and then connect to the p2pool network and send: "hey, my address is 1abcsomething and I'm mining difficulty 1000 and here is a share"? And then afterwards mine in secret a difficulty 650 share and connect to the p2pool network and send: "My address is 1xyzsomethingdifferent and I'm mining difficulty 650 and here is a share"?
How can you define a difficulty in advance, if you can simply reconnect with a new identity?
I'm sure I'm missing something here. Please enlighten me

How would that be different from connecting as 1abcsomething, saying "I'm mining at difficulty 1" and then submitting the diff=650 and diff=1000 shares? Doesn't p2pool take the actual share difficulty into account when calculating payouts?