What does it mean that "the tangle is network-bound instead of hash-power-bound like blockchain"?

Question

Can someone explain me in a very simple way what should an attacker do to double spend in IOTA?

In the whitepaper I read that a double spend transaction should outweigh the legitimate subtangle. Supposing all transactions have the same weight, malicious transaction should be confirmed by more transactions than the honest one. Why doesn't spamming the network with a lot of transactions confirming the double spend work?

Why is the IOTA tangle said to be network-bound instead of hash power bound? Does it mean that i can issue enough transactions confirming the double spend because of weak proof-of-work but i will never be able to spread them across the nodes quickly enough because network is a bottleneck?

Answer 1

The IOTA Tangle more network-bound than hash-power-bound because in order to perform an attack, you need to meet three conditions:

• X [any number] percentage of network hash rate (depending on Y 34% may not be enough)
• Omnipresence
  You have to know how a big section of the network topology (know which nodes are neighbours of which nodes)
• Y percentage of omnipotence (being neighboured to a certain percentage of the right (Omnipresence) full nodes)

(If you have a lot of X, you need less of Y and vice versa)

Whereas in blockchains, you would only need enough hash power to generate your own blocks faster than the rest of the network.
Furthermore, there is an economic incentive (block reward) in Bitcoin. This encourages hash-power-monopolies.

Details