cloud computing Cloud computing is "a paradigm for enabling network access to a scalable and elastic pool of shareable physical or virtual resources with self-service provisioning and administration on-demand," according to International Organization for ...

, the term zero-knowledge (or occasionally no-knowledge or zero access) is a commonly used term for

online services An online service provider (OSP) can, for example, be an Internet service provider, an email provider, a news provider (press), an entertainment provider (music, movies), a search engine, an e-commerce site, an online banking site, a health site, ...

that store,

transfer Transfer may refer to: Arts and media * ''Transfer'' (2010 film), a German science-fiction movie directed by Damir Lukacevic and starring Zana Marjanović * ''Transfer'' (1966 film), a short film * ''Transfer'' (journal), in management studies * ...

or manipulate

data Data ( , ) are a collection of discrete or continuous values that convey information, describing the quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted for ...

with a high level of

confidentiality Confidentiality involves a set of rules or a promise sometimes executed through confidentiality agreements that limits the access to or places restrictions on the distribution of certain types of information. Legal confidentiality By law, la ...

, where the data is only accessible to the data's owner (the

client Client(s) or The Client may refer to: * Client (business) * Client (computing), hardware or software that accesses a remote service on another computer * Customer or client, a recipient of goods or services in return for monetary or other valuable ...

), and not to the service provider. However, unlike "

end-to-end encryption End-to-end encryption (E2EE) is a method of implementing a secure communication system where only communicating users can participate. No one else, including the system provider, telecom providers, Internet providers or malicious actors, can ...

", the term "zero-knowledge" does not imply any specific threat model or security notion, and its use is commonly frowned-upon by the security community. The term "zero-knowledge" was popularized by

backup In information technology, a backup, or data backup is a copy of computer data taken and stored elsewhere so that it may be used to restore the original after a data loss event. The verb form, referring to the process of doing so, is "wikt:back ...

service

SpiderOak SpiderOak Inc. is a US-based software company focused on satellite cybersecurity. The company began in 2006 as a producer of a collaboration tool, online backup and file hosting service that allows users to access and share data using a cloud- ...

, which later switched to using the term "no knowledge", acknowledging that the previous terminology was not technically accurate.

Disadvantages

Most

cloud storage Cloud storage is a model of computer data storage in which data, said to be on "the cloud", is stored remotely in logical pools and is accessible to users over a network, typically the Internet. The physical storage spans multiple servers (so ...

services keep a copy of the client's password on their servers, allowing clients who have lost their passwords to retrieve and decrypt their data using alternative means of

authentication Authentication (from ''authentikos'', "real, genuine", from αὐθέντης ''authentes'', "author") is the act of proving an Logical assertion, assertion, such as the Digital identity, identity of a computer system user. In contrast with iden ...

; but since zero-knowledge services ''do not'' store copies of clients' passwords, if a client loses their password then their data cannot be decrypted, making it practically unrecoverable. Most

services are also able to furnish access requests from

law enforcement Law enforcement is the activity of some members of the government or other social institutions who act in an organized manner to enforce the law by investigating, deterring, rehabilitating, or punishing people who violate the rules and norms gove ...

agencies for similar reasons; zero-knowledge services, however, are unable to do so, since their systems are designed to make clients' data inaccessible without the client's explicit cooperation.

References

{{reflist, * * * {{Cite news , last=Farivar , first=Cyrus , date=2016-10-04 , title=FBI demands Signal user data, but there's not much to hand over , language=en-us , work=Ars Technica , url=https://arstechnica.com/tech-policy/2016/10/fbi-demands-signal-user-data-but-theres-not-much-to-hand-over/ , access-date=2021-05-29 Privacy Computer security Backup software Secure communication Internet terminology