Editing Secret sharing (section)

{{short description|Method for sharing a secret in a way that requires multiple parties to collaborate to recover it}}
{{for|cases when the whole secret is known by all participants|shared secret}}
{{more citations needed|date=February 2019}}

'''Secret sharing''' (also called '''secret splitting''') refers to methods for distributing a [[secrecy|secret]] among a group, in such a way that no individual holds any intelligible information about the secret, but when a sufficient number of individuals combine their 'shares', the secret may be reconstructed. Whereas ''insecure'' secret sharing allows an attacker to gain more information with each share, ''secure'' secret sharing is 'all or nothing' (where 'all' means the necessary number of shares).

In one type of secret sharing scheme there is one ''dealer'' and ''n'' ''players''. The dealer gives a share of the secret to the players, but only when specific conditions are fulfilled will the players be able to reconstruct the secret from their shares. The dealer accomplishes this by giving each player a share in such a way that any group of ''t'' (for ''threshold'') or more players can together reconstruct the secret but no group of fewer than ''t'' players can. Such a system is called a {{nowrap|(''t'', ''n'')}}-threshold scheme (sometimes it is written as an {{nowrap|(''n'', ''t'')}}-threshold scheme).

Secret sharing was invented independently by [[Adi Shamir]]<ref>{{cite journal |last1=Shamir |first1=Adi |title=How to share a secret |journal=Communications of the ACM |date=1 November 1979 |volume=22 |issue=11 |pages=612–613 |doi=10.1145/359168.359176 |s2cid=16321225 |url=https://cs.jhu.edu/~sdoshi/crypto/papers/shamirturing.pdf |url-status=live |archive-url=https://web.archive.org/web/20170810232803/http://cs.jhu.edu/~sdoshi/crypto/papers/shamirturing.pdf |archive-date=2017-08-10}}</ref> and [[George Blakley]]<ref>{{cite journal |last1=Blakley |first1=G.R. |title=Safeguarding Cryptographic Keys |journal=Managing Requirements Knowledge, International Workshop on (AFIPS) |volume=48 |pages=313–317 |date=1979 |doi=10.1109/AFIPS.1979.98 |s2cid=38199738 |url=https://pdfs.semanticscholar.org/32d2/1ccc21a807627fcb21ea829d1acdab23be12.pdf |archive-url=https://web.archive.org/web/20180628164048/https://pdfs.semanticscholar.org/32d2/1ccc21a807627fcb21ea829d1acdab23be12.pdf |url-status=dead |archive-date=2018-06-28 }}</ref> in 1979.
[[File:Visual crypto animation demo.gif|frame|right|A demonstration of [[visual cryptography]]: when two same-sized [[binary image]]s of apparently random black-and-white pixels are superimposed, the [[Wikipedia]] logo appears]]