On 9 August, the co-founder of IOHK and the creator of the Cardano protocol, Charles Hoskinson shot on Twitter against Vitalik Buterin's accusations in Ouroboros. In July, Buterin published some points regarding Ouroboros against Casper on the subreddit of Ethereum.
Team A: Ouroboros; used by Cardano
Team B: Casper; used by Ethereum
Both algorithms are based on the Proof of the Stake protocol.
In response to this, Hoskinson tweeted a post containing the official confutation of Cardano to Buterin. The blog is titled "How does Casper to appear with Ouroboros?". Here, Ouroboros has been defined as "a formally specified protocol and analyzed with mathematically proven security guarantees based on clearly specified assumptions"
Rebuttal to Vitalik: https://t.co/hNhyCLU6Kv
– Charles Hoskinson (@ IOHK_Charles) 9 August 2018
On the other hand, Cardano wrote that at the moment there are no published sources that provide a description of how Casper works. In addition, the blog said that Casper holds a weaker guarantee than Ouroboros on how much it is necessary to check the stake to make the protocol work smoothly. Against this, Vitalik Buterin replied to Twitter and replied on Hoskinson's tweet, saying:
Cardano said that "persistence and liveliness" are the two fundamental properties required for the establishment of any consensus protocol based on the PoS. While persistence determines the immutability and purpose of the ledger, the liveliness adds the verified transactions to that immutable ledger.
Under "Pole Assumptions", Cardano wrote that Ouroboros possesses the foundations of persistence and liveliness through hypothesis of an honest majority of all bets in the system. On the other hand, in Casper, honest parties control only a small part of the deposited pile. The opposite of Buterin, as stated by him, is:
"There is absolutely no (i) * incentive * ownership, (ii) hypothesis of network synchrony"
Cardano also mentioned, under "Network Assumptions" that Casper has not defined network settings in which it operates and follows a similar approach in pointing out the defense mechanisms against long-range attacks. In this regard, Buterin has openly denied the points mentioned on Casper and commented:
"This is just a lie, for example, page 4 of the Casper FFG document:" Plausible vibrancy means that regardless of previous events (eg cut events, **** delayed blocks ****, censorship attacks, etc.) ""
Here are a few other tweet-threads published by Buterin that oppose Cardano's refutation:
On the sucreddit of Ethereum, Buterin also said that a post on Reddit in which he tried to understand Cardano has not yet been followed. Although the Cardano team wrote the "hit" article, it did not answer all the questions asked by Buterin. He considered this as a pedantic approach to the question, rather than a sincere one to understand the Casper protocol.
The original post Reddit of Buterin can be seen here: