EtherDelata Exchange is truly decentralized. Metamask browser wallet is used to store your crypto assets, all private keys are stored locally in your computer. The trading logics implemented in smart contract launched in Ethereum virtual machine. BUT you can trade only those tokens created in the same contract, i.e. almost all ERC20 tokens and Ether. We utilize all this functionality AND also allow cross-chain trading using atomic swaps. For example, you can change ETH into BTC and at the same time still have your keys stored in your computer. Unfortunately, Metamask can only operate Ethereum blockchain and its test nets (Ropsten, for instance). That’s why we will create our own browser extension for Google Chrome. The extension can be activated in any browser on Chromium engine (Yandex browser). Well known in crypto community Brave browser will soon move to this engine. In addition, EtherDelta Exchange works very slowly due to constant requests to the smart contract. We provide high-speed operating by using Lightning Network protocol. So operating speed will only depend on your Internet connection and will equal operating speed of any centralized exchange.
If we talk about DEX Exchange we can safely say it is a centralized platform. When you add funds to your account wallet you send your assets to cold wallets of the Exchange. There are three server systems responsible for the safety of your funds. In return of your real funds you get credits – assets of Waves blockchain. These three servers are also responsible for the reverse conversion. You trade credits, not your crypto assets. Credits should equal real cryptocurrency price which they don’t. And nothing stops Alexander Ivanov from taking your real assets and shutting down the server, leaving you with the credits. Developers of DEX platform call their Exchange decentralized just because it uses blockchain for trading.
Different between centralize and decentralized - the most important difference is where is users coins. Centralized - keep all coins on their wallets and one day they can disappear with users money. Decentralized (truly decentralized) do not keep any users assets, users trade directly from their own browser wallets.