The validity of each cryptocurrency's coins is provided by a blockchain. A blockchain is a continuously growing list of records, called blocks, which are linked and secured using cryptography. Each block typically contains a hash pointer as a link to a previous block, a timestamp and transaction data. By design, blockchains are inherently resistant to modification of the data. It is "an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way". For use as a distributed ledger, a blockchain is typically managed by a peer-to-peer network collectively adhering to a protocol for validating new blocks. Once recorded, the data in any given block cannot be altered retroactively without the alteration of all subsequent blocks, which requires collusion of the network majority.
Assets are invested in any eligible U.S. dollar-denominated money market instruments as defined by applicable U.S. Securities and Exchange Commission regulations (Rule 2a-7 of the Investment Company Act of 1940), including all types listed above as well as commercial paper, certificates of deposit, corporate notes, and other private instruments from domestic and foreign issuers, as well as repurchase and potentially reverse repurchase agreements.
Money market mutual funds own a well-diversified pool of high quality, short-dated, interest-paying securities, and pass along the income earned on those securities (after fees) to the funds’ shareholders. When the yields on the securities in which money market mutual funds invest are quite low, the yields that the funds are passing along to their shareholders are also quite low. The interest rate policy of the Federal Reserve (the Fed) is a key driver for money market rates.
In February 2014 the world's largest bitcoin exchange, Mt. Gox, declared bankruptcy. The company stated that it had lost nearly $473 million of their customers' bitcoins likely due to theft. This was equivalent to approximately 750,000 bitcoins, or about 7% of all the bitcoins in existence. The price of a bitcoin fell from a high of about $1,160 in December to under $400 in February.
Fund yields are typically somewhat higher than bank savings accounts, but of course these are different products with differing risks (e.g., money fund accounts are not insured and are not deposit accounts). Since Retail funds generally have higher servicing needs and thus expenses than Institutional funds, their yields are generally lower than Institutional funds.
If this sounds similar to banks’ high-yield savings accounts or money market accounts, it is. The largest difference lies in the ability for yields on money market mutual funds to rise proportionately with interest rates. For example, as interest rates have risen, the yields on most bank money market accounts (which are set by the banks themselves) have stayed relatively flat, while money market mutual fund yields have increased.