[Cryptography] DAG vs Blockchain

[Valentin Pasquale]

"However isn't mining the thing that incentivizes increased computing power to verify the blockchain and protect against a 51% attack?"

Actually, you can "mine" with stack of coin (that's PoS of dPoS). Ethereum is trying to implement this kind of mining

"Would DAGs be less secure against attackers with lots of computing power *because* there is no mining?"

Same, if a system is based on something (let say mining) then yes dag is easier to attack. With hashgraph you need to be 34%. But some people claim every distributed system is vulnerable to a 34% attack, consisting in setting up a firewall separating honest miners in two groups, and then attack of the group. Such a firewall can be pretty hard to set, so blockchain is more secure.
But dag is designed to be "fast" and therefore isn't based on mining but rather on stack or reputation (for permissioned systems, a group of founders can have 20% of the reputation they share when they invite people in). Moreover I think proof of stake or proof of work achieve the same level of security regardless of how one can attack it (PoS can be insecure if they are massive hacks, and PoW can be insecure if one guy achieve to improve the "mining algorithm" and sell it. Personally I prefer proof of work)

TLWR : "No". Yes.
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