It is just a once off thing.

A better way to think of it is that the POW stage is an initial "fair" giveaway stage.  Once it is done, the checkpoint is part of the protocol.

The chain is defined as having a particular hash as genesis and that block 50000 hashes to .  The only difference is that it takes a while to find the 50000th block.

If you joined after the 50000th block, there is no difference between the hard-coding the genesis block into the client (which Bitcoin does too) and hard-coding the 50000th block.

It is fully p2p after the 50000th block.


There is only 1 checkpoint and it has to be signed by the original developer (or group of trusted individuals).  They promise to only sign one checkpoint.

The ISP can't fake that signature.  The checkpoint signature would be part of the protocol.

They can't really stop you from getting the signature.  It only happens once, and they would have to scan everything that goes to you to block it.  This would require blocking you from making any encrypted connection at all.  That isn't feasible.