li pping , ▁zero - know ledge ▁proofs , ▁and ▁secure ▁computation . ▁ ▁A ▁way ▁to ▁visual ize ▁a ▁commit ment ▁scheme ▁is ▁to ▁think ▁of ▁a ▁sender ▁as ▁putting ▁a ▁message ▁in ▁a ▁locked ▁box , ▁and ▁giving ▁the ▁box ▁to ▁a ▁receiver . ▁The ▁message ▁in ▁the ▁box ▁is ▁hidden ▁from ▁the ▁receiver , ▁who ▁cannot ▁open ▁the ▁lock ▁themselves . ▁Since ▁the ▁receiver ▁has ▁the ▁box , ▁the ▁message ▁inside ▁cannot ▁be ▁changed — mer ely ▁revealed ▁if ▁the ▁sender ▁cho oses ▁to ▁give ▁them ▁the ▁key ▁at ▁some ▁later ▁time . ▁ ▁Inter actions ▁in ▁a ▁commit ment ▁scheme ▁take ▁place ▁in ▁two ▁phases : ▁▁ ▁the ▁commit ▁phase ▁during ▁which ▁a ▁value ▁is ▁chosen ▁and ▁specified ▁ ▁the ▁reve al ▁phase ▁during ▁which ▁the ▁value ▁is ▁revealed ▁and ▁checked ▁ ▁In ▁simple ▁protocol s , ▁the ▁commit ▁phase ▁consists ▁of ▁a ▁single ▁message ▁from ▁the ▁sender ▁to ▁the ▁receiver . ▁This ▁message ▁is ▁called ▁the ▁commit ment . ▁It ▁is ▁essential ▁that ▁the ▁specific ▁value ▁chosen ▁cannot ▁be ▁known ▁by ▁the ▁receiver ▁at ▁that ▁time ▁( this ▁is ▁called ▁the ▁hiding ▁property ). ▁A ▁simple ▁reve al ▁phase ▁would ▁consist ▁of ▁a ▁single ▁message , ▁the ▁opening , ▁from ▁the ▁sender ▁to ▁the ▁receiver , ▁followed ▁by ▁a ▁check ▁performed ▁by ▁the ▁receiver . ▁The ▁value ▁chosen ▁during ▁the ▁commit ▁phase ▁must ▁be ▁the ▁only ▁one ▁that ▁the ▁sender ▁can ▁compute ▁and ▁that ▁valid ates ▁during ▁the ▁reve al ▁phase ▁( this ▁is ▁called ▁the ▁binding ▁property