The developer of the Bitcoin cash wallet application, Jonald Fyookball, once again criticized SegWit, believing that the segregated witness "actually removed an Integrity check in the Bitcoin book." He wrote that assuming a miner ignores the witness data of the transaction block, this eliminates the possibility of non-miners verifying their authenticity.
Fyookball, developer of Bitcoin cash wallet Electron Cash, had previously disagreed with SegWit. He believes that SegWit has weakened Bitcoin's security and made Bitcoin technically not like Bitcoin as defined by Satoshi Nakamoto in the 2008 White Paper. His statements are consistent with other Bitcoin cash supporters and developers.
A few days ago, he published an article on Yours.org expressing his thoughts.
Although the miners have been responsible for verifying the integrity of all past and present transactions, the emergence of SegWit means that they are more responsible. If the miners are careless, malicious, forced, or have experienced software bugs that caused the signature to “witness” unpublished, how can we verify that 100% of the transactions are valid? This is also the case when 51% of attacks occur - it only needs to happen once to destroy trust.
If the miner ignores the reason for the witness data can be accepted, the chain may continue without witness data. If it is later found incorrect, is the chain bifurcated? Or will it continue to be as it is?
This is similar to putting on belts and slings for many years to make sure that your trousers won't fall out, and then one day to relieve the belt and declare "I'm still wearing a sling, what will happen?"
Although this is a rare or even impossible situation, it is possible. "It is undeniable that the security model has changed," writes Fyookball. SegWit means users can prove their cryptocurrency hosting, but not the managed chain. This means removing an honest integrity check, which is critical for all databases, especially Bitcoin.
Not yet happening, but there is a possibility
Fyookball admits that so far he has not yet described the situation and said that he does not want to exaggerate this issue.
"There are always some trade-offs. Some people may think that SegWit is an acceptable trade-off. They think Bitcoin has a large enough number of archive nodes, so the lack of witness data is never a problem."
He concludes that it is ironic that Bitcoin core developers are driving non-mining “full node” operators and developers, but they are willing to take on additional responsibilities for miners. Some Bitcoin core supporters also discourage the use of SPV wallets (most mobile wallets) with a secure mode that does not have a full blockchain record.