CompTIA Security_ Deluxe Study Guide_ SY0-201 - Emmett Dulaney [176]
Palm, Motorola, Cisco, and others have implemented, or are implementing, the ECC system for security. Palm handhelds can now form secure connections to applications running on other systems using wireless or other means. Motorola recently released its new development system for the next generation of cellular phones; this system implements ECC and other protocols as an integral part of the toolkit. You can expect that ECC will be commonly implemented in cellular devices in the near future.
El Gamal El Gamal is an algorithm used for transmitting digital signatures and key exchanges. The method is based on calculating logarithms. The process used is similar to the Diffie-Hellman key exchange and is based on the characteristics of logarithmic numbers and calculations. The El Gamal algorithm was first published in 1985. The Digital Signature Algorithm (DSA) is based on El Gamal.
Using Cryptographic Systems
A cryptographic system is a system, method, or process that is used to provide encryption and decryption. It may be a hardware, software, or manually performed process. Cryptographic systems exist for the same reasons that security exists: to provide confidentiality, integrity, authentication, nonrepudiation, and access control. The following sections discuss these issues within the framework of cryptographic systems.
Confidentiality
One of the major reasons to implement a cryptographic system is to ensure the confidentiality of the information being used. Confidentiality may be intended to prevent the unauthorized disclosure of information in a local network or to prevent the unauthorized disclosure of information across a network. A cryptographic system must do this effectively in order to be of value.
The need to keep records secure from internal disclosure may be just as great as the need to keep records secure from outside attacks. The effectiveness of a cryptographic system in preventing unauthorized decryption is referred to as its strength: A strong cryptographic system is difficult to crack. Strength is also referred to as the algorithm’s work factor: The work factor describes an estimate of the amount of time and effort that would be needed to break a system.
The system may be considered weak if it allows weak keys, has defects in its design, or is easily decrypted. Many systems available today are more than adequate for business and personal use, but they are inadequate for sensitive military or governmental applications.
Integrity
The second major reason for implementing a cryptographic system involves providing assurance that a message wasn’t modified during transmission. Modification may render a message unintelligible or, even worse, inaccurate. Imagine the consequences if record alterations weren’t discovered in medical records involving drug prescriptions. If a message is tampered with, the encryption system should have a mechanism to indicate that the message has been corrupted or altered.
Integrity can be accomplished by adding information such as checksums or redundant data that can be used as part of the decryption process. Figure 7.6 gives a simple example of how integrity can be validated in a message. Notice that data about the message length and the number of vowels in the message are included in the message.
FIGURE 7.6 A simple integrity-checking process for an encrypted message
These two additions to the message provide a two-way check on the integrity of the message. In this case, the message has somehow become corrupted or invalidated. The original message had 12 characters; the decrypted message has 13 characters. Of course, the processes used in a real system are much more complicated. The addition of this information could be considered a signature of a sort.
A common method of verifying integrity involves adding a message authentication code (MAC) to the message. The MAC is derived from the message and a key. In Figure