a.PKI architecture
Entity
An entity is an end user of PKI products or services, such as a person, an organization, a device like a router or a switch, or a process running on a computer.
CA
A certificate authority (CA) is a trusted authority responsible for issuing and managing digital certificates. A CA issues certificates, specifies the validity periods of certificates, and revokes certificates as needed by publishing CRLs.
RA
A registration authority (RA) is an extended part of a CA or an independent authority. An RA can implement functions including identity authentication, CRL management, key pair generation and key pair backup. It only examines the qualifications of users; it does not sign certificates. Sometimes, a CA assumes the registration management responsibility and no independent RA exists. The PKI standard recommends that an independent RA be used for registration management to achieve higher security of application systems.
PKI repository
A PKI repository can be a Lightweight Directory Access Protocol (LDAP) server or a common database. It stores and manages information like certificate requests, certificates, keys, CRLs and logs, and it provides a simple query function.
LDAP is a protocol for accessing and managing PKI information. An LDAP server stores user information and digital certificates from the RA server and provides directory navigation service. From an LDAP server, an entity can retrieve digital certificates of its own and other entities.
Applications of PKI
The PKI technology can satisfy the security requirements of online transactions. As an infrastructure, PKI has a wide range of applications. Here are some application examples.
VPN
A virtual private network (VPN) is a private data communication network built on the public communication infrastructure. A VPN can leverage network layer security protocols (for instance, IPSec) in conjunction with
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