A cryptocurrency (or crypto currency) is a digital asset designed to work as a medium of exchange that uses strong cryptography to secure financial transactions, control the creation of additional units, and verify the transfer of assets.[1][2][3] Cryptocurrencies are a kind of alternative currency and digital currency (of which virtual currency is a subset). Cryptocurrencies use decentralized control[4] as opposed to centralized digital currency and central banking systems.[5] The decentralized control of each cryptocurrency works through distributed ledger technology, typically a blockchain, that serves as a public financial transaction database.[6][7]
As of May 2018, over 1,800 cryptocurrency specifications existed.[29] Within a cryptocurrency system, the safety, integrity and balance of ledgers is maintained by a community of mutually distrustful parties referred to as miners: who use their computers to help validate and timestamp transactions, adding them to the ledger in accordance with a particular timestamping scheme.[16]

The above futures curve shows that in the short term (< 1month) bitcoin-USD futures prices tend to be at or higher than the respective spot prices, with the highest premium to spot reached for futures maturing in approximately 9 days. In the mid term (1-3 months), bitcoin futures prices increase rapidly with mid prices at a premium of approximately 2% compared to the spot price. In the long term (>3months), premiums are positive and prices increase with a relatively stable velocity. Long term prices are at a slightly higher level compared to mid-term maturities. The absolute difference between long-term and short-term premium is positive, revealing an overall positive view about bitcoin among investors for the future. To summarize, this curve reflects modest investor optimism in the short term, due to a possibly high level of volatility around the launch of U.S.-listed bitcoin futures contracts, and an increasingly positive view on bitcoin-USD rates in the medium and long term. In the distant future (>3months) the curve may reflect a belief that the long-term true value of bitcoin will be at a higher level than today, possibly due to increased institutional participation and the maturation of digital assets as a potential asset class.

Mortgage-backed securities are most commonly issued or guaranteed by GNMA, FNMA or the Federal Home Loan Mortgage Corporation (“FHLMC”), but may also be issued or guaranteed by other private issuers. GNMA is a government-owned corporation that is an agency of the U.S. Department of Housing and Urban Development. It guarantees, with the full faith and credit of the United States, full and timely payment of all monthly principal and interest on its mortgage-backed securities. FNMA is a publicly owned, government-sponsored corporation that mostly packages mortgages backed by the Federal Housing Administration, but also sells some non-governmentally backed mortgages. Pass-through securities issued by FNMA are guaranteed as to timely payment of principal and interest only by FNMA. The FHLMC is a publicly chartered agency that buys qualifying residential mortgages from lenders, re-packages them and provides certain guarantees. The corporation’s stock is owned by savings institutions across the United States and is held in trust by the Federal Home Loan Bank System. Pass-through securities issued by the FHLMC are guaranteed as to timely payment of principal and interest only by the FHLMC.
Making money arbitraging bitcoin futures can be extremely simple. Futures contracts typically trade at a premium, and all you have to do, starting with USD, is buy bitcoin at Spot price and sell futures of the same amount at premium price. Then just wait until expiration to make your arb profit in bitcoin (which you can then put in USD). Whether it's a weekly, monthly, quarterly, or any futures contract, as long as it's in a premium, you lock in the sale price and earn the arbitrage profit.