Page 216 - DCAP403_Operating System

Unit 11: System Security

Figure 11.1: Denial of Service Attack Notes

11.5 Cryptography as a Security Tools

Internet provides essential communication between tens of millions of people and is being
increasingly used as a tool for commerce, security becomes a tremendously important issue to
deal with.
There are many aspects to security and many applications, ranging from secure commerce and
payments to private communications and protecting passwords. One essential aspect for secure
communications is that of cryptography.
When your computer sends the information out, it scrambles it by using some key. This scrambled
information would be gibberish to anyone who didn’t have the correct key to unscramble it at
the other end.
When the information reaches its destination, it gets unscrambled by using the key. This lets the
person or website read the information correctly at the other end.
Websites that use an encrypted connection use something called SSL (Secure Sockets Layer) to
secure the information going back and forth. This is how websites like Amazon or your bank can
ensure your private information like passwords and credit card numbers are safe from prying
eyes.
Cryptography can play many different roles in user authentication. Cryptographic authentication
systems provide authentication capabilities through the use of cryptographic keys known or
possessed only by authorized entities.

Cryptography also supports authentication through its widespread use in other authentication
systems.

Example: Password systems often employ cryptography to encrypt stored password

files, card/token system often employ cryptography to protect sensitive stored information,
and hand-held password generators often employ cryptography to generate random, dynamic
passwords.

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