Public key certificate

In email encryption, code signing, and e-signature systems, a certificate's subject is typically a person or organization.

The protocol requires the server to present a digital certificate, proving that it is the intended destination.

[clarification needed] The hostname must be publicly accessible, not using private addresses or reserved domains.

Once the certification path validation is successful, the client can establish an encrypted connection with the server.

Because most services provide access to individuals, rather than devices, most client certificates contain an email address or personal name rather than a hostname.

[5] While most web browsers support client certificates, the most common form of authentication on the Internet is a username and password pair.

Client certificates are more common in virtual private networks (VPN) and Remote Desktop Services, where they authenticate devices.

[8] Google Chrome version 58 (March 2017) removed support for checking the commonName field at all, instead only looking at the SANs.

[citation needed] Only a single level of subdomain matching is supported in accordance with RFC 2818.

As of 2011, partial wildcard support is optional, and is explicitly disallowed in SubjectAltName headers that are required for multi-name certificates.

[20] All major browsers have deliberately removed support for partial-wildcard certificates;[21][22] they will result in a "SSL_ERROR_BAD_CERT_DOMAIN" error.

Similarly, it is typical for standard libraries in programming languages to not support "partial-wildcard" certificates.

International domain names encoded in ASCII (A-label) are labels that are ASCII-encoded and begin with xn--.

Validated information about the website's owner (SSL Corp) is located in the Subject field.

Other CAs are trusted within a relatively small community, like a business, and are distributed by other mechanisms like Windows Group Policy.

The policies and processes a provider uses to decide which certificate authorities their software should trust are called root programs.

The most influential root programs are:[citation needed] Browsers other than Firefox generally use the operating system's facilities to decide which certificate authorities are trusted.

[29] Edge and Safari use their respective operating system trust stores as well, but each is only available on a single OS.

Root programs generally provide a set of valid purposes with the certificates they include.

[34] If revocation information is unavailable (either due to accident or an attack), clients must decide whether to fail-hard and treat a certificate as if it is revoked (and so degrade availability) or to fail-soft and treat it as unrevoked (and allow attackers to sidestep revocation).

The certificate request is an electronic document that contains the web site name, company information and the public key.

As an example, when a user connects to https://www.example.com/ with their browser, if the browser does not give any certificate warning message, then the user can be theoretically sure that interacting with https://www.example.com/ is equivalent to interacting with the entity in contact with the email address listed in the public registrar under "example.com", even though that email address may not be displayed anywhere on the web site.

A certificate provider will issue an organization validation (OV) class certificate to a purchaser if the purchaser can meet two criteria: the right to administratively manage the domain name in question, and perhaps, the organization's actual existence as a legal entity.

Until 2019, major browsers such as Chrome and Firefox generally offered users a visual indication of the legal identity when a site presented an EV certificate.

This was done by showing the legal name before the domain, and a bright green color to highlight the change.

Most browsers deprecated this feature[37][38] providing no visual difference to the user on the type of certificate used.

This change followed security concerns raised by forensic experts and successful attempts to purchase EV certificates to impersonate famous organizations, proving the inefficiency of these visual indicators and highlighting potential abuses.

All web browsers come with an extensive built-in list of trusted root certificates, many of which are controlled by organizations that may be unfamiliar to the user.

[43] In spite of the limitations described above, certificate-authenticated TLS is considered mandatory by all security guidelines whenever a web site hosts confidential information or performs material transactions.

[44] The National Institute of Standards and Technology (NIST) Computer Security Division[45] provides guidance documents for public key certificates: