Why the user's private keys are sent to your server ?
Hello Malyx, thank you for your question.
You can use your private key, keystore file, metamask to log into our exchange, just like every decentralized exchange offers this login, similar to myetherwallet. We can't collecting or saving anything from this details.
That's not true. Private keys are sent to the server, then you use a token to identify the user. So you store them: