Do you mean Bitcoin or cryptocurrencies generally? For the Bitcoin protocol itself, then I don't believe there are any trustless solutions. The protocol delibe

Do you mean Bitcoin or cryptocurrencies generally? For the Bitcoin protocol itself, then I don't believe there are any trustless solutions. The protocol deliberately promotes pooling with no disincentive to growth. As such, you have two options. One is fundamentally change the protocol to not incentivise large pools. This may be possible but it's not really Bitcoin at that point (unless you consider it just a brand in which case all bets are off). The other option, and is essentially the current one, is to rely on the fact that the big mining pools are incentivised to not, publicly, screw up the block chain. Obviously, there's nothing trustless about this but, as long as the motives of the miners is overwhelmingly financial, this will probably work fine.