10.5 SECURITY ISSUES

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Security is of paramount importance because systems are prone to attacks. The various security threats can be the following:

Interruption: The intended recipient is not allowed to receive the data— this is an attack on the availability of the system.

Interception: The intended recipient receives the data, but unauthorized persons also receive the data—this is an attack on the confidentiality of the data.

Modification: An unauthorized person receives the data, modifies it, and then sends it to the intended recipient—this is an attack on the integrity of the data.

Fabrication: An unauthorized person generates the data and sends it to a person—this is an attack on the authenticity of the system.

To overcome these security threats, the data has to be encrypted. Encryption is a mechanism wherein the user data is transformed using an encryption key. Only those who have the encryption key can decrypt the data.

There are two possibilities: link encryption and end-to-end encryption. In link encryption, at the transmitting end, the data is encrypted and sent over the communication link. At the receiving end of the link, the data is decrypted. In end-to-end encryption, the user encrypts the data and sends it over the communication link, and the recipient decrypts the data. To provide high security, both types of encryption can be employed. Note that encryption does not increase the data rate (or bandwidth). Length of the encryption key decides how safe the encryption mechanism is. Though 56- and 64-bit keys were used in earlier days, now 512- and 1024-bit keys are being used for highly secure communication systems.

The major security threats are: interruption, interception, modification, and fabrication. The data is encrypted at the transmitting end to overcome these security threats. At the receiving end, the data is decrypted.

We will study security issues in detail in Chapter 38, "Information Security."

Note

For encryption, there will be an encryption algorithm and an encryption key. The encryption algorithm specifies the procedure for modifying the data using an encryption key. The algorithm can be made public (known to everyone), but the encryption key is kept secret.

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