Long position of BTCHASH means longing the block mining reward in BTC, while shorting the mining difficulty, as the block mining reward is negatively proportional to the mining difficulty. Long 1 BTCHASH at a certain maturity date means long the block mining reward for 1 PH/s hash rate for the next difficulty resetting period (2016 blocks, roughly 14 days) following the maturity date. Note that BTCHASH only include the block reward, or 6.25 BTC per block at the moment, but not the transaction fees in each block. Electricity and other operational cost are also omitted.

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