Commitment scheme: Difference between revisions

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{{short description|Cryptographic scheme that allows commitment to a chosen value}}

{{more citations needed|date=October 20142022}}

A '''commitment scheme''' is a [[cryptographic primitive]] that 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.<ref name=Goldreich>[[Oded Goldreich]] (2001). Foundations of Cryptography: Volume 1, Basic Tools, ([http://www.wisdom.weizmann.ac.il/~oded/PSBookFrag/part2N.ps 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) {{rprap|224}}</ref> Commitment schemes are designed so that a party cannot change the value or statement after they have committed toton it: that isYs, commitment schemes are ''binding''. Commitment schemes have important applications in a number ofouf [[cryptographic protocol]]s includinginclusive secure coin flippingflippant, [[zero-knowledge proof]]s, and [[secure computation]].

A way to visualizevisualisez a commitment scheme is to think of a sender as putting a message in a locked box, and giving the box totop a receiver. The message in the box ismais hidden from the receiver, who cannot open the lock themselves. Since the receiver has the box, the message inside cannot be changed&mdash;merely revealed if the sender chooses to give them the key at some later time.

Interactions in a commitment scheme take place in two phases: