i + r / b + f - h . ▁ ▁i ▁is ▁the ▁number ▁of ▁initial ▁r ounds ▁ ▁r ▁is ▁the ▁number ▁of ▁r ounds ▁per ▁block ▁ ▁b ▁is ▁the ▁block ▁size ▁in ▁bytes , ▁defined ▁for ▁{ 1 , ▁ 2 , ▁ 3 , ▁... ▁ 1 2 8 } ▁ ▁f ▁is ▁the ▁number ▁of ▁final ▁r ounds ▁ ▁h ▁is ▁the ▁size ▁of ▁the ▁hash ▁output ▁in ▁bits , ▁defined ▁for ▁{ 8 , ▁ 1 6 , ▁ 2 4 , ▁ 3 2 , ▁... ▁ 5 1 2 } ▁In ▁the ▁original ▁N IST ▁submission , ▁i ▁and ▁f ▁was ▁fixed ▁to ▁ 1 0 r . ▁The ▁ob sole te ▁notation ▁C ube Has hr / b - h ▁indicates ▁i ▁and ▁f ▁being ▁implicitly ▁ 1 0 r . ▁ ▁The ▁internal ▁state ▁is ▁defined ▁as ▁a ▁five - dimensional ▁array ▁of ▁words ▁( four - byte ▁integers ), ▁ 0 - 1 ▁in ▁both ▁dimensions . ▁The ▁words ▁are ▁referred ▁to ▁with ▁their ▁coordinates ▁[ 0 0 0 0 0 ] ▁to ▁[ 1 1 1 1 1 ]. ▁The ▁words ▁are ▁treated ▁as ▁little - end ian . ▁ ▁The ▁internal ▁state ▁is ▁initialized ▁by ▁setting ▁the ▁first ▁three ▁words ▁([ 0 0 0 0 0 ], ▁[ 0 0 0 0 1 ], ▁[ 0 0 0 1 0 ]) ▁to ▁h / 8 , ▁b , ▁and ▁r ▁respectively , ▁all ▁other ▁words ▁to ▁zero . ▁