Root certificate
Encyclopedia
In cryptography
and computer security
, a root certificate is either an unsigned public key certificate
or a self-signed certificate
that identifies the Root Certificate Authority
(CA). A root certificate is part of a public key infrastructure
scheme. The most common commercial variety is based on the ITU-T
X.509
standard, which normally includes a digital signature
from a certificate authority
(CA).
Digital certificates are verified using a chain of trust
. The trust anchor
for the digital certificate is the Root Certificate Authority (CA).
A certificate authority
can issue multiple certificates in the form of a tree structure
. A root certificate is the top-most certificate of the tree, the private key of which is used to "sign" other certificates. All certificates immediately below the root certificate inherit the trustworthiness of the root certificate - a signature by a root certificate is somewhat analogous to "notarizing" an identity in the physical world. Certificates further down the tree also depend on the trustworthiness of the intermediates (often known as "subordinate certification authorities").
Many software applications assume these root certificates are trustworthy on the user's behalf. For example, a Web browser
uses them to verify identities within SSL/TLS
secure connections. However, this implies that the user trusts their browser's publisher, the certificate authorities it trusts, and any intermediates the certificate authority may have issued a certificate-issuing-certificate, to faithfully verify the identity and intentions of all parties that own the certificates. This (transitive
) trust in a root certificate is the usual case and is integral to the X.509 certificate chain model.
The root certificate is usually made trustworthy by some mechanism other than a certificate, such as by secure physical distribution. For example, some of the most well-known root certificates are distributed in the Internet browsers by their manufacturers.
Cryptography
Cryptography is the practice and study of techniques for secure communication in the presence of third parties...
and computer security
Computer security
Computer security is a branch of computer technology known as information security as applied to computers and networks. The objective of computer security includes protection of information and property from theft, corruption, or natural disaster, while allowing the information and property to...
, a root certificate is either an unsigned public key certificate
Public key certificate
In cryptography, a public key certificate is an electronic document which uses a digital signature to bind a public key with an identity — information such as the name of a person or an organization, their address, and so forth...
or a self-signed certificate
Self-signed certificate
In cryptography and computer security, a self-signed certificate is an identity certificate that is signed by its own creator. That is, the person that created the certificate also signed off on its legitimacy....
that identifies the Root Certificate Authority
Certificate authority
In cryptography, a certificate authority, or certification authority, is an entity that issues digital certificates. The digital certificate certifies the ownership of a public key by the named subject of the certificate...
(CA). A root certificate is part of a public key infrastructure
Public key infrastructure
Public Key Infrastructure is a set of hardware, software, people, policies, and procedures needed to create, manage, distribute, use, store, and revoke digital certificates. In cryptography, a PKI is an arrangement that binds public keys with respective user identities by means of a certificate...
scheme. The most common commercial variety is based on the ITU-T
ITU-T
The ITU Telecommunication Standardization Sector is one of the three sectors of the International Telecommunication Union ; it coordinates standards for telecommunications....
X.509
X.509
In cryptography, X.509 is an ITU-T standard for a public key infrastructure and Privilege Management Infrastructure . X.509 specifies, amongst other things, standard formats for public key certificates, certificate revocation lists, attribute certificates, and a certification path validation...
standard, which normally includes a digital signature
Digital signature
A digital signature or digital signature scheme is a mathematical scheme for demonstrating the authenticity of a digital message or document. A valid digital signature gives a recipient reason to believe that the message was created by a known sender, and that it was not altered in transit...
from a certificate authority
Certificate authority
In cryptography, a certificate authority, or certification authority, is an entity that issues digital certificates. The digital certificate certifies the ownership of a public key by the named subject of the certificate...
(CA).
Digital certificates are verified using a chain of trust
Chain of trust
In computer security, a chain of trust is established by validating each component of hardware and software from the bottom up. It is intended to ensure that only trusted software and hardware can be used while still remaining flexible.-Introduction:...
. The trust anchor
Trust Anchor
In cryptography, a trust anchor is an authoritative entity represented via a public key and associated data. It is used in the context of public key infrastructures, X.509 digital certificates and DNSSEC....
for the digital certificate is the Root Certificate Authority (CA).
A certificate authority
Certificate authority
In cryptography, a certificate authority, or certification authority, is an entity that issues digital certificates. The digital certificate certifies the ownership of a public key by the named subject of the certificate...
can issue multiple certificates in the form of a tree structure
Tree structure
A tree structure is a way of representing the hierarchical nature of a structure in a graphical form. It is named a "tree structure" because the classic representation resembles a tree, even though the chart is generally upside down compared to an actual tree, with the "root" at the top and the...
. A root certificate is the top-most certificate of the tree, the private key of which is used to "sign" other certificates. All certificates immediately below the root certificate inherit the trustworthiness of the root certificate - a signature by a root certificate is somewhat analogous to "notarizing" an identity in the physical world. Certificates further down the tree also depend on the trustworthiness of the intermediates (often known as "subordinate certification authorities").
Many software applications assume these root certificates are trustworthy on the user's behalf. For example, a Web browser
Web browser
A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier and may be a web page, image, video, or other piece of content...
uses them to verify identities within SSL/TLS
Transport Layer Security
Transport Layer Security and its predecessor, Secure Sockets Layer , are cryptographic protocols that provide communication security over the Internet...
secure connections. However, this implies that the user trusts their browser's publisher, the certificate authorities it trusts, and any intermediates the certificate authority may have issued a certificate-issuing-certificate, to faithfully verify the identity and intentions of all parties that own the certificates. This (transitive
Transitive relation
In mathematics, a binary relation R over a set X is transitive if whenever an element a is related to an element b, and b is in turn related to an element c, then a is also related to c....
) trust in a root certificate is the usual case and is integral to the X.509 certificate chain model.
The root certificate is usually made trustworthy by some mechanism other than a certificate, such as by secure physical distribution. For example, some of the most well-known root certificates are distributed in the Internet browsers by their manufacturers.