While physical coins sound like a good idea, they force you to trust the honesty of the creator of the coin. If I were trading on a regular basis, this would really eat into my profit margins. We can buy the most popular cryptocurrencies on Kraken or Coinbase, but the latter comes with a wider range available. You must sell using either a bank account or a USD account that will hold your money on Coinbase. Coinbase knows your addresses and balance at all times and can connect this with your identity and IP address. Add Comment. Whether you choose Kraken or Coinbase, you should not keep your currency in either of these online wallets for a long period of time.