 in cryptography, a commitment scheme allows one to commit to a chosen value (or chosen statement) while keeping it hidden to others, with the ability to reveal the committed value later.oded goldreich (2001). foundations of cryptography: volume 1, basic tools, (draft available from author's site). cambridge university press. isbn 0-521-79172-3. (see also http://www.wisdom.weizmann.ac.il/~oded/foc-book.html)  commitment schemes are designed so that a party cannot change the value or statement after they have committed to it: that is, commitment schemes are binding. commitment schemes have important applications in a number of cryptographic protocols including secure coin flipping, zero-knowledge proofs, and secure computation. commitment schemes and their possible applications can be demonstrated with a simple example: say that two people want to play rock-paper-scissors by email. the problem with trying to do so, is that one player may simply wait until they receive the other's email of, say, "rock" and then quickly reply with, say, "paper", winning the game. this problem can be overcome by commitment schemes. at the beginning of the game, each player commits to rock, paper, or scissors. after they have done so, each reveals the choice that they committed to earlier. it is not possible to cheat because as mentioned, commitment schemes are binding. interactions in a commitment scheme take place in two phases: # the commit phase during which a value is chosen and specified # the reveal phase during which the value is revealed and checked in simple protocols, the commit phase consists of a single message from the sender to the receiver. this message is called the commitment. 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 reveal 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 validates during the reveal phase (this is called the binding property). the concept of commitment schemes was first formalized by gilles brassard, david chaum, and claude crepeau in 1988,gilles brassard, david chaum, and claude crepeau, minimum disclosure proofs of knowledge, journal of computer and system sciences, vol. 37, pp. 156â189, 1988. but the concept was used without being treated formally prior to that.claude crÃ©peau, commitment, mcgill.ca, accessed april 11, 2008 the notion of 
Cryptographic_primitives Public-key_cryptography Secret_sharing Zero-knowledge_protocols