===== Public Key =====
[[dido:public:ra:xapend:xapend.a_glossary:start| Return to Glossary ]]

==== Definition 1 ====
A **Public Key**((
Elaine Barker,
NIST,
__Recommendation for Key Management: Part 1 - General__,
NIST Special Publication 800-57 Part 1, Revision 5,
May 2020,
Accessed 18 January 2022,
[[https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57pt1r5.pdf]]
)).
is a cryptographic key used with a **Public Key** [[dido:public:ra:xapend:xapend.a_glossary:c:cryptographic_algorithm]]
that is uniquely associated with an entity and that may be made public.
In an asymmetric-key (**Public Key**) cryptosystem, the **Public Key** has a
corresponding [[dido:public:ra:xapend:xapend.a_glossary:p:private_key#definition_1 | Private Key]]. The **Public Key** may be known by anyone
and, depending on the algorithm, may be used, for example:

  - Verify a digital signature that was generated using the corresponding [[dido:public:ra:xapend:xapend.a_glossary:p:private_key#definition_1 | Private Key]],
  - Encrypt keys that can be decrypted using the corresponding [[dido:public:ra:xapend:xapend.a_glossary:p:private_key#definition_1 | Private Key]], or
  - Compute a shared secret during a key-agreement transaction.

==== Definition 2 ====

In [[dido:public:ra:xapend:xapend.a_glossary:c:cryptography|cryptography]], a **Public Key** is a large numerical value that is used to encrypt data. The [[dido:public:ra:xapend:xapend.a_glossary:k:key|key]] can be generated by a software program, but more often, it is provided by a trusted, designated authority and made available to everyone through a publicly accessible repository or directory.

A **Public Key** is also used to encrypt a message or check the legitimacy of a [[dido:public:ra:xapend:xapend.a_glossary:d:digital_signature|digital signature]]. It is accompanied by a corresponding [[dido:public:ra:xapend:xapend.a_glossary:p:private_key|private key]], which is known only to its owner. Private keys are used to decrypt messages that were created with the corresponding **Public Key** or to create signatures. In other words, a **Public Key** locks up data from unauthorized use, while a private key is used to unlock it.

**Public Keys** are available from a [[dido:public:ra:xapend:xapend.a_glossary:c:ca]], which issues [[dido:public:ra:xapend:xapend.a_glossary:d:digital_certificate]] that prove the owner's identity and contain the owner's **Public Key**. **Public Keys** are created using an asymmetric algorithm, which pairs the **Public Key** with an associated private key. The most common algorithms used to generate **Public Key** are Rivest-Shamir-Adleman, elliptic curve cryptography, and Digital Signature Algorithm.

A **Public Key** can be given to any person with whom an individual wants to communicate, whereas a private key belongs to the individual it was created for and isn't shared. The **Public Key** is typically stored on a [[dido:public:ra:xapend:xapend.a_glossary:p:pki]] [[dido:public:ra:xapend:xapend.a_glossary:s:server|server]] and is used to encrypt data securely before it is sent over the [[dido:public:ra:xapend:xapend.a_glossary:i:internet|internet]].

Source: [[https://searchsecurity.techtarget.com/definition/public-key ]]


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