, ▁she ▁wins , ▁otherwise ▁Bob ▁wins ▁ ▁If ▁Alice ▁and ▁Bob ▁are ▁not ▁in ▁the ▁same ▁place ▁a ▁problem ▁ar ises . ▁Once ▁Alice ▁has ▁" called " ▁the ▁coin ▁f lip , ▁Bob ▁can ▁st ip ulate ▁the ▁f lip ▁" results " ▁to ▁be ▁whatever ▁is ▁most ▁des irable ▁for ▁him . ▁Similarly , ▁if ▁Alice ▁doesn ' t ▁announ ce ▁her ▁" call " ▁to ▁Bob , ▁after ▁Bob ▁f li ps ▁the ▁coin ▁and ▁announ ces ▁the ▁result , ▁Alice ▁can ▁report ▁that ▁she ▁called ▁whatever ▁result ▁is ▁most ▁des irable ▁for ▁her . ▁Alice ▁and ▁Bob ▁can ▁use ▁commit ments ▁in ▁a ▁procedure ▁that ▁will ▁allow ▁both ▁to ▁trust ▁the ▁outcome : ▁▁ ▁Alice ▁" c alls " ▁the ▁coin ▁f lip ▁but ▁only ▁tells ▁Bob ▁a ▁commit ment ▁to ▁her ▁call , ▁ ▁Bob ▁f li ps ▁the ▁coin ▁and ▁reports ▁the ▁result , ▁ ▁Alice ▁reve als ▁what ▁she ▁committed ▁to , ▁ ▁Bob ▁ver ifies ▁that ▁Alice ' s ▁call ▁matches ▁her ▁commit ment , ▁ ▁If ▁Alice ' s ▁revel ation ▁matches ▁the ▁coin ▁result ▁Bob ▁reported , ▁Alice ▁wins ▁ ▁For ▁Bob ▁to ▁be ▁able ▁to ▁ske w ▁the ▁results ▁to ▁his ▁favor , ▁he ▁must ▁be ▁able ▁to ▁understand ▁the ▁call ▁hidden ▁in ▁Alice ' s ▁commit ment . ▁If ▁the ▁commit ment ▁scheme ▁is ▁a ▁good ▁one , ▁Bob ▁cannot ▁ske w ▁the ▁results . ▁ ▁Similarly , ▁Alice ▁cannot ▁affect ▁the ▁result ▁if ▁she ▁cannot ▁change ▁the ▁value ▁she