Public Key Infrastructure (PKI) uses asymmetric key encryption between parties. The originator encrypts information using the intended recipient's "public" key in order to get confidentiality of the data being sent. The recipients use their own "private" key to decrypt the information. The "Infrastructure" of this methodology ensures that:
Correct Answer: C
Through the use of Public Key Infrastructure (PKI) the recipient's identity can be positively verified by the sender. The sender of the message knows he is using a Public Key that belongs to a specific user. He can validate through the Certification Authority (CA) that a public key is in fact the valid public key of the receiver and the receiver is really who he claims to be. By using the public key of the recipient, only the recipient using the matching private key will be able to decrypt the message. When you wish to achieve confidentiality, you encrypt the message with the recipient public key. If the sender would wish to prove to the recipient that he is really who he claims to be then the sender would apply a digital signature on the message before encrypting it with the public key of the receiver. This would provide Confidentiality and Authenticity of the message. A PKI (Public Key Infrastructure) enables users of an insecure public network, such as the Internet, to securely and privately exchange data through the use of public key-pairs that are obtained and shared through a trusted authority, usually referred to as a Certificate Authority. The PKI provides for digital certificates that can vouch for the identity of individuals or organizations, and for directory services that can store, and when necessary, revoke those digital certificates. A PKI is the underlying technology that addresses the issue of trust in a normally untrusted environment. The following answers are incorrect: The sender and recipient have reached a mutual agreement on the encryption key exchange that they will use. Is incorrect because through the use of Public Key Infrastructure (PKI), the parties do not have to have a mutual agreement. They have a trusted 3rd party Certificate Authority to perform the verification of the sender. The channels through which the information flows are secure. Is incorrect because the use of Public Key Infrastructure (PKI) does nothing to secure the channels. The sender of the message is the only other person with access to the recipient's private key. Is incorrect because the sender does not have access to the recipient's private key though Public Key Infrastructure (PKI). Reference(s) used for this question: OIG CBK Cryptography (pages 253 - 254)
Question 537
Which backup method copies only files that have changed since the last full backup, but does not clear the archive bit?
Correct Answer: A
Explanation/Reference: One of the key item to understand regarding backup is the archive bit. The archive bit is used to determine what files have been backuped already. The archive bit is set if a file is modified or a new file is created, this indicates to the backup program that it has to be saved on the next backup. When a full backup is performed the archive bit will be cleared indicating that the files were backup. This allows backup programs to do an incremental or differential backup that only backs up the changes to the filesystem since the last time the bit was cleared Full Backup (or Reference Backup) A Full backup will backup all the files and folders on the drive every time you run the full backup. The archive bit is cleared on all files indicating they were all backuped. Advantages: All files from the selected drives and folders are backed up to one backup set. In the event you need to restore files, they are easily restored from the single backup set. Disadvantages: A full backup is more time consuming than other backup options. Full backups require more disk, tape, or network drive space. Incremental Backup An incremental backup provides a backup of files that have changed or are new since the last incremental backup. For the first incremental backup, all files in the file set are backed up (just as in a full backup). If you use the same file set to perform a incremental backup later, only the files that have changed are backed up. If you use the same file set for a third backup, only the files that have changed since the second backup are backed up, and so on. Incremental backup will clear the archive bit. Advantages: Backup time is faster than full backups. Incremental backups require less disk, tape, or network drive space. You can keep several versions of the same files on different backup sets. Disadvantages: In order to restore all the files, you must have all of the incremental backups available. It may take longer to restore a specific file since you must search more than one backup set to find the latest version of a file. Differential Backup A differential backup provides a backup of files that have changed since a full backup was performed. A differential backup typically saves only the files that are different or new since the last full backup. Together, a full backup and a differential backup include all the files on your computer, changed and unchanged. Differential backup do not clear the archive bits. Advantages: Differential backups require even less disk, tape, or network drive space than incremental backups. Backup time is faster than full or incremental backups. Disadvantages: Restoring all your files may take considerably longer since you may have to restore both the last differential and full backup. Restoring an individual file may take longer since you have to locate the file on either the differential or full backup. For more info see: http://support.microsoft.com/kb/136621 Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 69.
Question 538
What is the most secure way to dispose of information on a CD-ROM?
Correct Answer: D
Explanation/Reference: First you have to realize that the question is specifically talking about a CDROM. The information stored on a CDROM is not in electro magnetic format, so a degausser woud be inneffective. You cannot sanitize a CDROM but you might be able to sanitize a RW/CDROM. A CDROM is a write once device and cannot be overwritten like a hard disk or other magnetic device. Physical Damage would not be enough as information could still be extracted in a lab from the undamaged portion of the media or even from the pieces after the physical damage has been done. Physical Destruction using a shredder, your microwave oven, melting it, would be very effective and the best choice for a non magnetic media such as a CDROM. Source: TIPTON, Hal, (ISC)2, Introduction to the CISSP Exam presentation.
Question 539
Physically securing backup tapes from unauthorized access is obviously a security concern and is considered a function of the:
Correct Answer: A
Section: Risk, Response and Recovery Explanation/Reference: Physically securing the tapes from unauthorized access is obviously a security concern and is considered a function of the Operations Security Domain. Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 71.
Question 540
What type of cable is used with 100Base-TX Fast Ethernet?
Correct Answer: C
This is the type of cabling recommended for 100Base-TX networks. Fiber-optic cable is incorrect. Incorrect media type for 100Base-TX -- 100Base-FX would denote fiber optic cabling. "Category 3 or 4 unshielded twisted-pair (UTP)" is incorrect. These types are not recommended for 100Mbps operation. RG-58 cable is incorrect. Incorrect media type for 100Base-TX. References CBK, p. 428 AIO3, p. 455
