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Chapter 8 Securing Information Systems 351

FIGURE 8.7 DIGITAL CERTIFICATES

Digital certificates help establish the identity of people or electronic assets. They protect online
transactions by providing secure, encrypted, online communication.

percent availability. In online transaction processing, transactions entered
online are immediately processed by the computer. Multitudinous changes to
databases, reporting, and requests for information occur each instant.
Fault-tolerant computer systems contain redundant hardware, software,
and power supply components that create an environment that provides
continuous, uninterrupted service. Fault-tolerant computers use special soft-
ware routines or self-checking logic built into their circuitry to detect hardware
failures and automatically switch to a backup device. Parts from these comput-
ers can be removed and repaired without disruption to the computer system.
Fault tolerance should be distinguished from high-availability comput-
ing. Both fault tolerance and high-availability computing try to minimize
downtime. Downtime refers to periods of time in which a system is not opera-
tional. However, high-availability computing helps firms recover quickly from a
system crash, whereas fault tolerance promises continuous availability and the
elimination of recovery time altogether.
High-availability computing environments are a minimum requirement for
firms with heavy e-commerce processing or for firms that depend on digital
networks for their internal operations. High-availability computing requires
backup servers, distribution of processing across multiple servers, high-capacity
storage, and good disaster recovery and business continuity plans. The firm’s
computing platform must be extremely robust with scalable processing power,
storage, and bandwidth.
Researchers are exploring ways to make computing systems recover even
more rapidly when mishaps occur, an approach called recovery-oriented
computing. This work includes designing systems that recover quickly, and
implementing capabilities and tools to help operators pinpoint the sources of
faults in multi-component systems and easily correct their mistakes.

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