X.500 Security Feature

The X.500 protocol was approved in 1988 before it got enhanced in 1993 under the International Telecommunications Union (ITU).The purpose is to provide an international standard for directory systems. The protocol consists of a Client-Server communicating via the Open Systems Interconnection (OSI) networking model. The Client is called the Directory Service Agent (DUA) and the Server is called the Directory System Agent (DSA).

Some of the protocol used in X.500 are:

• LDAP - Lightweight Directory Access Protocol
• DAP - Directory Access Protocol
• DSP - Directory System Protocol
• DISP - Directory Information Shadowing Protocol

 Security

The X.500 protocol uses the X.509 Public Key Infrastructure (PKI) specification (i.e. digital certificates) for authentication. The X.500 protocol provides for database replication. This means that directory data can be replicated or copies distributed to multiple servers for the purpose of load distribution and system contingency.

 

A typical X.500 session may proceed like the following:

• Client: Connects and requests access to the server; this is called the Binding operation.
• Server: Server authenticates the client and completes the binding operation.
• Client: Requests a service from the server, such as search for an entry in the directory, and presents any parameter data.
• Server: Performs service and may connect to another X.500 server then communicates a response.
• Client: Receives response and unbinds or terminates the connection. 

Reference
http://www.collectionscanada.gc.ca/iso/ill/document/ill_directory/X_500andLDAP.pdf