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Combining Cex and Dex is nonsense and pure trap, why create a seed for me that is connected to the internet and it's coming from an exchange, who will belive such that it's safe for me to use it as back up when I know that it will have a back door. Very soon, we will start to hear from customers that they have started to lose their coins that are been kept in exchanges.
Cex and Dex two different world, they should never coexist even for once.
But in fact, now many popular Exchange platforms such as Binance combine CEX and DEX and are now also available with Web3 which makes it easier for users to connect to Binance using the address created on Binance's Dex.
It all depends on whether people want to use it or not.
Problems with security or vulnerability to hacking, it's a choice of whether to use it or not.
Now new investors are no longer critical of CEX or DEX issues, they can only use what has been created and provided, especially with quite complete features.
But all do need to be aware and your key is not your asset. DWYOR.