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 while
providing 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 local and CA certificates of its own as well as certificates of other
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.
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 PKI-based encryption and digital signature technologies for confidentiality.
E-mails require confidentiality, integrity, authentication, and non-repudiation. PKI can address these
needs. The secure E-mail protocol that is currently developing rapidly is Secure/Multipurpose Internet
Mail Extensions (S/MIME), which is based on PKI and allows for transfer of encrypted mails with
For Web security, two peers can establish a Secure Sockets Layer (SSL) connection first for
transparent and secure communications at the application layer. With PKI, SSL enables encrypted
communications between a browser and a server. Both the communication parties can verify the
identity of each other through digital certificates.
Operation of PKI
In a PKI-enabled network, an entity can request a local certificate from the CA and the device can check
the validity of certificates. Here is how it works:
An entity submits a certificate request to the RA.
The RA reviews the identity of the entity and then sends the identity information and the public key
with a digital signature to the CA.
The CA verifies the digital signature, approves the application, and issues a certificate.
The RA receives the certificate from the CA, sends it to the LDAP server to provide directory
navigation service, and notifies the entity that the certificate is successfully issued.
The entity retrieves the certificate. With the certificate, the entity can communicate with other
entities safely through encryption and digital signature.
The entity makes a request to the CA when it needs to revoke its certificate, while the CA approves
the request, updates the CRLs and publishes the CRLs on the LDAP server.
PKI Configuration Task List
Complete the following tasks to configure PKI: