1 9 8 9 ▁while ▁working ▁at ▁X ero x ' s ▁Pal o ▁Al to ▁Research ▁Center . ▁Al ong ▁with ▁S ne f ru , ▁a ▁crypt ographic ▁hash ▁function , ▁the ▁ci ph ers ▁were ▁named ▁after ▁the ▁Egypt ian ▁Ph ara oh s ▁Kh uf u , ▁Kh af re ▁and ▁S ne fer u . ▁ ▁Under ▁a ▁volunt ary ▁scheme , ▁X ero x ▁submitted ▁Kh uf u ▁and ▁Kh af re ▁to ▁the ▁US ▁National ▁Security ▁Agency ▁( NS A ) ▁prior ▁to ▁publication . ▁NS A ▁requested ▁that ▁X ero x ▁not ▁publish ▁the ▁algorithms , ▁cit ing ▁concerns ▁about ▁national ▁security . ▁X ero x , ▁a ▁large ▁contract or ▁to ▁the ▁US ▁government , ▁comp lied . ▁However , ▁a ▁rev iewer ▁of ▁the ▁paper ▁passed ▁a ▁copy ▁to ▁John ▁Gil more , ▁who ▁made ▁it ▁available ▁via ▁the ▁sci . c rypt ▁news group . ▁It ▁would ▁appear ▁this ▁was ▁against ▁Mer k le ' s ▁wishes . ▁The ▁scheme ▁was ▁subsequently ▁published ▁at ▁the ▁ 1 9 9 0 ▁C RY P TO ▁conference ▁( M erk le , ▁ 1 9 9 0 ). ▁ ▁Kh uf u ▁and ▁Kh af re ▁were ▁pat ented ▁by ▁X ero x ; ▁issued ▁on ▁March ▁ 2 6 , ▁ 1 9 9 1 . ▁ ▁Kh uf u ▁ ▁Kh uf u ▁is ▁a ▁ 6 4 - bit ▁block ▁ci pher ▁which , ▁unus ually , ▁uses ▁keys ▁of ▁size