Prevention

• Disable or block any unused network services.

• Observe your system performance and establish baselines for ordinary activity. Use the baseline to gauge unusual levels of disk activity, CPU usage, or network traffic.

• Routinely examine your physical security with respect to your current needs (for example, servers, routers, unattended terminals, network access points).

6.2 Security Technologies

There are many methods to strengthen the security of the computer systems or a network of computer systems. In this section, you will learn the various ways computer systems are secured via encryption and authentication.

Reading Sequence: 6.2.1 Encryption. Learning Goal: Obtain understanding of data encryption methods.  Parsons/Oja, Chapter 5 - Section E. Remark: A general overview on encryption.  6.2.2 Applications of Encryption. Learning Goal: Become aware of uses of encryption in software applications as well as hardware devices such as DVD movies and cellular phones. 6.2.3 Authentication. Learning Goal: Knowledge of different methods used for authentication. This includes digital signatures, secure-socket layer (SSL) protocol, smart cards, and Biometrics.

                                      

Assessments: Multiple-Choice Quiz 23

6.2.1 Encryption

• Substitution Cipher

• Transmitting the Key

• Private Key Encryption Scheme

• Public Key Encryption Scheme

• Hybrid Encryption Schemes

Because unauthorized individuals may be "listening" to your data packets, information transmitted over a computer network is not always secure. There are many points in a computer network where communications can be intercepted. To address this problem, sensitive information must be encrypted prior to transmission, and then decrypted by the receiver. Encryption is the process of transforming information so it is unintelligible to eavesdroppers. Decryption is the process of transforming encrypted information so that it is intelligible to the intended recipient. A message to be encrypted is known as plaintext, and the encrypted version is called ciphertext. (A cipher is a secret code.) In order to encrypt a message in a way that the receiver can decrypt it again, there must be a key, or password, that determines how the encryption is done.

Communication via secret code has a long history, dating back at least to the ancient Greeks. Spurred by the need for greater security, an entire subfield of mathematics and computer science has grown up around cryptography. Cryptography algorithms are mathematical functions used for encryption or decryption. These mathematical calculations can be quite complicated, because they must eliminate any detectable patterns in the ciphertext that could make the code easy to break. One popular encryption algorithm for use in electronic commerce is DES, which stands for Data Encryption Standard. It was developed by the US government for applications, including secure communication applications, between government and financial institutions. Another popular encryption algorithm for computers, especially for Internet applications, is RC4. It was developed by a private company, RSA Security, Inc.

To learn more about the basics of cryptography, a good source of online information is the Cryptography FAQ.

In the remainder of this section, we will first look at some simple encryption schemes, and see why they are not good enough to meet today's security requirements. Then we will examine some encryption schemes being used today.