Read the full thread on Battle.net
Kerrigan 		December 1st, 2012 at 1:23am http://us.battle.net/d3/en/blog/7597724
"Players will be able to encounter the Keywardens in any difficulty, but only in Inferno and with a full five stacks of Nephalem Valor will they have a chance to drop pieces of the Infernal Machine. While Monster Power is not required, each level will increase the drop rate of both the keys and the plans by 10%, all the way up to a guaranteed 100% drop chance at Monster Power 10."

I thought the key drop rate is
mp0 = 5%
mp1 = 15% (5% + 10%)
mp2 = 25% (5% + 10% + 10%)
mp3 = 35%
mp4 = 45%
mp5 = 55%
mp6 = 65%
mp7 = 75%
mp8 = 85%
mp9 = 95%
mp10 = 100%

But on diablo forum, d2jsp forum, and etc people are saying the drop rates are
mp0 = 5%
mp1 = 10%
mp2 = 20%
mp3 = 30%
mp4 = 40%
mp5 = 50%
mp6 = 60%
mp7 = 70%
mp8 = 80%
mp9 = 90%
mp10 = 100%

I farm mp1 and the key drop rate seems to be 10%....

blue plz confirm this
Vaeflare 		December 1st, 2012 at 2:10am As other players have noted, the drop rate of keys and the plans is 5% on MP0, 10% on MP1, and 20% on MP2, all the way up through a 100% drop rate on MP10.