IOTA is cryptocurrency that uses a Tangle instead of a “blockchain”. From https://learn.iota.org/faqs, “The Tangle as implemented in IOTA is the first public distributed ledger to achieve scalability, no fee transactions, as well as quantum-computing protection”. In this article, I will try to investigate how they achieve this claim and see how correct their claim is.
I’m going to skip the “quantum-computing protection” part here because I’m not well versed in the topic, but let’s cover the two important topics. IOTA is proposing that the Tangle is a ledger that has “no fee transactions” and “achieves scalability”. These are two very contradictory statements because if there is no fee, there is nothing that prevents someone from spamming the network, and thus you have a ledger that grows out of control. Some shills have used “infinite scaling” ( https://www.iotasupport.org ) as a tagline, which is also a funny oxymoron.
So how does the IOTA Tangle work? When creating a transaction in IOTA, you must assemble any two transactions that came before it, and attach a small proof of work to it. Therefore, the creation of a transaction necessitates a creation of a very small block with two other transactions on it. This proof of work is a small constant (presumably so that it works on small devices to enable the Internet-of-things) and does not adjust to the network hash rate.
This raises an obvious question: so if the proof of work is a small constant, how does IOTA deal with the fact that someone with a lot of hashing power can spam the network with a bunch of transactions? The Tangle will quickly grow out of control preventing anybody from validating the full ledger. Oddly enough, the whitepaper https://iota.org/IOTA_Whitepaper.pdf makes only a single sentence mention of this attack and how it plans to deal with this. Here is the sentence: “To avoid spamming and other attack styles, it is assumed that no entity can generate an abundance of transactions with “acceptable” weights in a short period of time.”
Ehh… what? What kind of crazy assumption is that? So basically what the whitepaper is saying is that the proof of work has to be difficult enough to prevent spamming, even though the difficulty does not adjust automatically. This means that the Tangle has to hard fork every time there is some drastic change in the network hash rate. Anybody who’s ever mined a cryptocurency knows that the network hash rate can abruptly change at any time, so this assumption is just plain wrong. Another problem with this assumption is that if the proof of work is difficult enough to prevent spamming, it will also be too difficult for your typical Internet of things(the single application that IOTA is supposed to be for) device to solve.
After some looking and asking around, there seems to be another solution that IOTA is using to prevent spam attacks. The solution is the usual suspect when IOTA is being criticized and that is the central coordinator. IOTA’s central coordinator “decides” what is a spam transaction and removes it from being propagated through the network…. hmm doesn’t sound decentralized to me. I was going to bring this up with an IOTA developer, but it seems like I’m not the only one with this concern. Reddit user polayo expressed the same concerns about IOTA’s scaling when IOTA held its AMA, and an IOTA developer actually answered this question himself.
His answer basically states “We don’t have an answer right now. We are going to research this, but for now snapshots is our answer”. So there you have it. One of the main developers of IOTA is admitting that the Tangle does not achieve scalability in its current state. Their two excuses are that a) they are relying on “snapshots” and b) its part of some ongoing research which nobody knows about and they are not going to disclose (if you believe this, I have some Bitconnects to sell you).
“Snapshots” describe the state of a ledger at a certain time without you having to download the entire ledger. They are centralized solutions that relies on trust. Every time you download a snapshot you are putting yourself at diverging from consensus because you have to trust that you are getting the correct snapshot. Scaling is extremely easy when it doesn’t have to be trustless. Every cryptocurrency, including Bitcoin, scales just as well as IOTA’s Tangle if it relied on snapshots and hand-waved away the fact that snapshots are not trust-less (services like blockchain.info are essentially snapshotting services and no one's seriously proposing it as a scaling solution for Bitcoin).
Skimming through the IOTA roadmap, https://blog.iota.org/iota-development-roadmap-74741f37ed01 , they refer to snapshots several times but there is nothing in place to tell us how they will remove their dependencies from snapshots. There is also no plan whatsoever to deprecate their central coordinator which they rely on heavily to keep the network going.
In summary, when you strip away the fancy tech jargon like Directed Acylic Graphs, Internet of Things, and Tangle, what the IOTA whitepaper proposes is simple and fundamentally impossible. They are basically proposing that a blockchain with no difficulty adjustment can scale. When they actually implemented their system, they realized that this was impossible for an actual decentralized system so they implemented a centralized solution to fix it.
TLDR:
Does IOTA achieve better scalability compared to other cryptocurrencies? No.
Does IOTA achieve better scalability compared to other cryptocurrencies? No.
Does it heavily rely on a centralized coordinator? Yes.
Is there any plan in place to remove dependencies from the coordinator? No.
