Review on Qtum by Jerry Siegel
Qtum Overview
Qtum is basically Bitcoin on PoS combined with Ethereum. Developers came up with the idea to effectively (not so much) combine bitcoin-like transactions with ethereum-like smart-contracts.
Proof-of-Stake combined with UTXO is a pretty interesting idea, but only in theory. They using same transaction output mechanisms (UTXO) like Bitcoin, but confirming the network consensus by validators with higher stakes (PoS), not higher hashing power (PoW).
They also utilised the Virtual Machine from Ethereum (EVM), and modified it to be able to work with Bitcoin-like ledger. QTUM Foundation claims that they’ve been the first chain that enables dApps to work on PoS with UTXO technology, which they inherited from BTC. But there’s some shortcomings to that.
Vulnerabilities:
UTXO accounting mechanism is time-tested only in Proof-of-Work, but it hasn't been properly stress-tested with Proof-of-Stake protocols. Just like in Bitcoin, Qtum nodes are required to store UTXO database in RAM (random access memory) or disk memory. I’ve read an interesting report, that discovers vulnerabilities to this type of networks, for example “Fake Stake” attack. This attack can be done by any sophomore hacker: it filling up victim’s node disk or RAM with bogus data and subsequently causes severe data overload and leads to node crash. This report states that “Fake Stake” is very easy to perform, thus fundamentally undermine the development team’s design.
Conclusion:
I just don’t see any reason why any dApp developer should build applications on Qtum, instead of Ethereum. Qtum is using the same Solidity language, which was created by Ethereum. So why should any developer use this EVM copy instead of original Ethereum solution? Besides, there are some very serious vulnerabilities with UTXO + PoS chains, like “Fake Stake” attack, “Spent Stake” and many more. And I’m not even talking about the network scalability if (BIG IF) there will be any broad usage of Qtum dApps.
So my overall opinion is that this project needs to come up with something much more secure and create much more reliable blockchain solutions.
Pros
- Interesting idea with combining Bitcoin-like transactions with Ethereum-like smart-contracts
Cons
- Network is very vulnerable for hacker attacks, for example the possibility of overloading PoS nodes with bogus data
- Not enough marketing and PR, feels like they stuck in 2018
