▁enough ▁because ▁it ▁ex cludes ▁protocol s ▁that ▁explo it ▁the ▁principle ▁of ▁no - super l um inal ▁sign alling . ▁Kent ▁provided ▁the ▁first ▁un condition ally ▁secure ▁bit ▁commit ment ▁protocol ▁in ▁the ▁setting ▁of ▁relativ istic ▁crypt ography . ▁Vari ous ▁protocol s ▁for ▁bit ▁commit ment ▁have ▁been ▁de vised ▁by ▁Kent ▁and ▁others . ▁Ex perimental ▁demonstr ations ▁of ▁relativ istic ▁bit ▁commit ment ▁have ▁been ▁implemented . ▁ ▁Co in ▁toss ing ▁In ▁strong ▁coin ▁toss ing , ▁Alice ▁and ▁Bob ▁are ▁at ▁different ▁locations ▁and ▁they ▁wish ▁to ▁toss ▁a ▁coin ▁in ▁such ▁a ▁way ▁that ▁Alice ▁is ▁guaranteed ▁that ▁Bob ▁cannot ▁bias ▁the ▁outcome , ▁and ▁Bob ▁is ▁guaranteed ▁that ▁Alice ▁cannot ▁bias ▁the ▁outcome ▁either . ▁It ▁was ▁shown ▁by ▁Lo ▁and ▁Ch au ▁that ▁ideal ▁strong ▁coin ▁toss ing ▁is ▁impossible ▁to ▁achieve ▁with ▁un cond itional ▁security ▁based ▁only ▁on ▁the ▁laws ▁of ▁quantum ▁physics . ▁However , ▁Kent ▁over c ame ▁this ▁no - go ▁theorem ▁by ▁providing ▁a ▁relativ istic ▁protocol ▁for ▁strong ▁coin ▁toss ing ▁that ▁is ▁un condition ally ▁secure . ▁This ▁protocol ▁is ▁concept ually ▁very ▁simple ▁and ▁is ▁illustrated ▁here ▁as ▁an ▁example ▁of ▁a ▁protocol ▁in ▁relativ istic ▁crypt ography . ▁ ▁In ▁Kent ’ s ▁coin ▁toss ing ▁protocol , ▁Alice ▁has ▁two ▁agents ▁A 0 ▁and ▁A 1 , ▁and ▁Bob ▁has ▁two ▁agents ▁B 0 ▁and ▁B 1 . ▁A i ▁and ▁Bi ▁are ▁at ▁location ▁Li , ▁for ▁. ▁Let