Elements of Networking Security: Encryption, Authentication, and Integrity 

Elements of Networking Security: Encryption, Authentication, and Integrity

A firewall system is a hardware/software configuration that sits at perimeter between a company's network and the Computer Security, controlling access into and out of the network. Encryption can be understood as follows:
the coding of data through an algorithm or transform table into apparently unintelligible garbage
used on both data stored on a server or as data is communicated through a network
a method of ensuring privacy of data and that only intended users may view the information
Encryption mechanisms rely on keys or passwords. The longer the password, the more difficult the encryption is to break. DES relies on a 56-bit key length, and some mechanisms have keys that are hundreds of bits long. There are two kinds of encryption mechanisms used private key and public key. Private-key encryption uses the same key to encode and decode the data. Public-key encryption uses one key to encode the data and another to decode the data. The name public key comes from a unique property of this type of encryption mechanism namely; one of the keys can be public without compromising the privacy of the message or the other key. In fact, usually a trusted recipient, perhaps a remote office network gateway, keeps a private key to decode data as it comes from the main office employ encryption to provide secure transmissions over public networks such as the Internet.
Authentication and Integrity
Authentication is simply making sure users are who they say they are. When using resources or sending messages in a large private network, not to mention the Internet, authentication is of the utmost importance. Integrity knows that the data sent has not been altered along the way. Of course, a message modified in any way would be highly suspect and should be completely discounted. Message integrity is maintained with digital signatures. A digital signature is a block of data at the end of a message that attests to the authenticity of the file. If any change is made to the file, the signature will not verify. Digital signatures perform both an authentication and message integrity function. Digital signature functionality is available in PGP and when using RSA encryption. Kerberos is an add-on system that can be used with any existing network. Kerberos validates a user through its authentication system and uses DES when communicating sensitive information such as passwords and an open network. In addition, Kerberos sessions have a limited lifespan, requiring users to login after a predetermined length of time and disallowing would-be intruders to replay a captured session and thus gain unauthorized entry.