The first computer networks were used to send e-mails and share files and printers between researchers and corporate employees. In such a scenario security was not given much thought. Now the computer networks (especially the Internet) are used by millions for banking, shopping and filing their tax returns, and network security has become a major problem. Network security can be divided into four areas.. . .
The first computer networks were used to send e-mails and share files and printers between researchers and corporate employees. In such a scenario security was not given much thought. Now the computer networks (especially the Internet) are used by millions for banking, shopping and filing their tax returns, and network security has become a major problem. Network security can be divided into four areas.

Why do we need an authentication service? An authentication service verifies the identity of the communication partner. Authentication is a fundamental building block of a secure network environment. If a server knows for certain the identity of its client, it can decide whether to provide it a particular service (for example.. printing facility) or not, whether to give the user special privileges etc. As an aside authentication and authorization are different. If user Foo says "delete file bar", then the problem of verifying whether the command came from Foo is authentication. The problem of verifying whether Foo has permission to delete file bar is authorization.

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