This seems like a thoroughly thought out version of a DAG (directed acyclic graph) based currency. I don't have time to go through it with a fine toothed comb, but I'm curious about others' reactions.<p>There are well known problems with DAGs: lack of incentive to run full nodes, tip choice attacks, flooding/spam attacks if there are no fees, and many and varied types of Sybil attacks.<p>For flooding or spam a transaction proof of work isn't enough. Not only does it "waste" a lot of energy (though at the edge nodes where it's less visible than mining farms) which negates part of the purported benefit of a DAG, but it's vulnerable to ASICs or botnets. If you can short a cryptocurrency on any major exchange that supports short selling then it will get attacked with the goal not of stealing coins or censoring transactions but of just destroying it.<p>Tip choice attacks combined with Sybil attacks can be very sophisticated. Tip choice is "random" but randomness cannot be verified. 3, 18, 593, 3, 3, now prove those were not random numbers modulus 1024. You can't of course. So I can non-randomly choose the transactions I link to. If I combine this with some sophisticated analysis of the network's transaction structure and physical topology I might be able to skew the network in some disastrous way over time in ways that would be completely undetectable since my apparently "random" tip/link choices were not in fact random. Then I can do something like short the coin and do something nasty to the network.<p>Attackers can be very <i>very</i> creative, and attacks only get better.<p>Last but not least: there is no mining mechanism in a DAG coin, or at least I've never heard of how one could be done. This means DAG coins are "Big Bang" coins that begin with all the money that will ever exist. This is problematic from an economic point of view and opens a huge can of worms around what is done with that money and how it is distributed to initial holders.