▁the ▁coin ' s ▁first ▁creation . ▁ ▁While ▁hash c ash ▁uses ▁the ▁S HA - 1 ▁hash ▁and ▁requires ▁the ▁first ▁ 2 0 ▁of ▁ 1 6 0 ▁hash ▁bits ▁to ▁be ▁zero , ▁bit co in ' s ▁proof ▁of ▁work ▁uses ▁two ▁success ive ▁S HA - 2 5 6 ▁hash es ▁and ▁originally ▁required ▁at ▁least ▁the ▁first ▁ 3 2 ▁of ▁ 2 5 6 ▁hash ▁bits ▁to ▁be ▁zero . ▁However ▁the ▁bit co in ▁network ▁period ically ▁res ets ▁the ▁difficulty ▁level ▁to ▁keep ▁the ▁average ▁rate ▁of ▁block ▁creation ▁at ▁ 6 ▁per ▁hour . ▁As ▁of ▁January ▁ 2 0 2 0 ▁block ▁# 6 1 4 5 2 5 ▁the ▁bit co in ▁network ▁has ▁respond ed ▁to ▁deploy ments ▁of ▁ever ▁faster ▁has hing ▁hardware ▁by ▁min ers ▁by ▁hard ening ▁the ▁requirement ▁to ▁first ▁ 7 4 ▁of ▁ 2 5 6 ▁hash ▁bits ▁must ▁be ▁zero . ▁ ▁Sp am ▁filters ▁Hash c ash ▁is ▁used ▁as ▁a ▁potential ▁solution ▁for ▁false ▁posit ives ▁with ▁autom ated ▁sp am ▁filtering ▁systems , ▁as ▁legit imate ▁users ▁will ▁rarely ▁be ▁incon ven ien ced ▁by ▁the ▁extra ▁time ▁it ▁takes ▁to ▁mine ▁a ▁stamp . ▁Sp am Ass ass in ▁has ▁been ▁able ▁to ▁check ▁for ▁Hash c ash ▁st amps ▁since ▁version ▁ 2 . 7 0 , ▁assigning ▁a ▁negative ▁score ▁( i . e . ▁less ▁likely ▁to ▁be ▁sp am ) ▁for ▁valid , ▁un