All decentralized exchanges are safe because they operate on blockchain. They will have no access to your private key, don’t hold your personal information and account balance. All trades happen not on a centralized server but run on a distributed ledger.  I’ve checked out Ethen, they have a smart contract for trading https://etherscan.io/address/0xf4c27b8b002389864ac214cb13bfeef4cc5c4e8d#code, no registration, and an open code for withdrawing tokens https://ethenmarket.github.io/. Means your funds are safe.