Cryptography and Network Security”, 4/e, by William Stallings,

Cryptography and Network Security Background

• Information Security requirements have changed in recent times
• traditionally provided by physical and administrative mechanisms
• computer use requires automated tools to protect files and other stored information
• use of networks and communications links requires measures to protect data during transmission

The requirements of information security within an organization have undergone two major changes in the last several decades. Before the widespread use of data processing equipment,the security of information felt to be valuable to an organization was provided primarily by physical (eg. rugged filing cabinets with locks) and administrative mechanisms (eg. Personnel screening procedures during hiring process).

Growing computer use implies a need for automated tools for protecting files and other information stored on it. This is especially the case for a shared system, such as a time-sharing system, and even more so for systems that can be accessed over a public telephone network, data network, or the Internet.

The second major change that affected security is the introduction of distributed systems and the use of networks and communications facilities for carrying data between terminal user and computer and between computer and computer. Network security measures are needed to protect data during their transmission.