By Hannah Lang (Reuters) -One of the top decentralized cryptocurrency trading platforms, dYdX, is preparing to enter the U.S. market by the end of the year, in a shift for the derivatives-focused exchange that was previously not available to American users, the president of dYdX told Reuters in an interview. Unlike centralized exchanges like Coinbase and Kraken that act as the intermediary between buyers and sellers, decentralized platforms like dYdX aim to cut out the middleman and allow users to transa ...