> For the complete documentation index, see [llms.txt](https://dev.ishare.eu/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dev.ishare.eu/version-3.0/introduction/specific-technical-standards/x.509.md).

# X.509

In cryptography, X.509 is a standard defining the format of public key certificates. X.. 509 certificates are used in many Internet protocols, including TLS/SSL, which is the basis for HTTPS, the secure protocol for browsing the web. They are also used in offline applications, like electronic signatures. An X.509 certificate contains a public key and an identity (a hostname, an organisation, or an individual), and is either signed by a certificate authority or self-signed. When a certificate is signed by a trusted certificate authority, or validated by other means, someone holding that certificate can rely on the public key it contains to establish secure communications with another party, or validate documents digitally signed by the corresponding private key. The most recent version of this specification can be found at [tools.ietf.org (RFC 5280)](https://tools.ietf.org/html/rfc5280).

X. 509 is used in iSHARE as a standard defining the format of public key certificates.


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