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So in that sense, this approach is pretty cool. The biggest question mark is though ... if you are just checking the zkSNARK to see whether there exists a transaction chain all the way back to the genesis block, you are exposed to all sorts of attacks: the simplest one is most likely to just create a private side chain where you create a state that you want to spoof to someone else, and somehow submit this state along with perfectly valid zk-SNARKs to your victim. How in this world can he know that state is invalid and that there exists a different state with a "greater cumulative difficulty" containing the same coins spent to someone else (longest chain approach)? I cannot think of any way, but like I said, probably I am just not understanding it correctly