CompTIA RC0-C02 Exam Questions & Answers

Correct Answer: BD

Correct Answer: DE

We can use dynamic disk pools (DDP) to increase availability and improve performance compared to traditional RAID. Multipathing also improves availability by creating multiple paths to the storage (in case one path fails) and it improves the

performance by aggregating the performance of the multiple paths. DDP dynamically distributes all data, spare capacity, and protection information across a pool of drives. Effectively, DDP is a new type of RAID level, built on RAID 6. It uses

an intelligent algorithm to define where each chunk of data should reside. In traditional RAID, drives are organized into arrays, and logical drives are written across stripes on the physical drives in the array. Hot spares contain no data until a

drive fails, leaving that spare capacity stranded and without a purpose. In the event of a drive failure, the data is recreated on the hot spare, significantly impacting the performance of all drives in the array during the rebuild process.

With DDP, each logical drive's data and spare capacity is distributed across all drives in the pool, so all drives contribute to the aggregate IO of the logical drive, and the spare capacity is available to all logical drives. In the event of a physical

drive failure, data is reconstructed throughout the disk pool. Basically, the data that had previously resided on the failed drive is redistributed across all drives in the pool. Recovery from a failed drive may be up to ten times faster than a rebuild

in a traditional RAID set, and the performance degradation is much less during the rebuild.

In computer storage, multipath I/O is a fault-tolerance and performance-enhancement technique that defines more than one physical path between the CPU in a computer system and its mass-storage devices through the buses, controllers,

switches, and bridge devices connecting them.

As an example, a SCSI hard disk drive may connect to two SCSI controllers on the same computer, or a disk may connect to two Fibre Channel ports. Should one controller, port or switch fail, the operating system can route the I/O through

the remaining controller, port or switch transparently and with no changes visible to the applications.

Correct Answer: A

In cryptography, the one-time pad (OTP) is an encryption technique that cannot be cracked if used correctly. In this technique, a plaintext is paired with a random secret key (also referred to as a one-time pad). Then, each bit or character of

the plaintext is encrypted by combining it with the corresponding bit or character from the pad using modular addition. If the key is truly random, is at least as long as the plaintext, is never reused in whole or in part, and is kept completely

secret, then the resulting ciphertext will be impossible to decrypt or break. However, practical problems have prevented one-time pads from being widely used.

The "pad" part of the name comes from early implementations where the key material was distributed as a pad of paper, so that the top sheet could be easily torn off and destroyed after use.

The one-time pad has serious drawbacks in practice because it requires:

Truly random (as opposed to pseudorandom) one-time pad values, which is a non-trivial requirement.

Secure generation and exchange of the one-time pad values, which must be at least as long as the message. (The security of the one-time pad is only as secure as the security of the one-time pad exchange).

Careful treatment to make sure that it continues to remain secret, and is disposed of correctly preventing any reuse in whole or part--hence "one time".

Because the pad, like all shared secrets, must be passed and kept secure, and the pad has to be at least as long as the message, there is often no point in using one-time padding, as one can simply send the plain text instead of the pad (as

both can be the same size and have to be sent securely).

Distributing very long one-time pad keys is inconvenient and usually poses a significant security risk. The pad is essentially the encryption key, but unlike keys for modern ciphers, it must be extremely long and is much too difficult for humans

to remember. Storage media such as thumb drives, DVD-Rs or personal digital audio players can be used to carry a very large one-time-pad from place to place in a non-suspicious way, but even so the need to transport the pad physically is

a burden compared to the key negotiation protocols of a modern public-key cryptosystem, and such media cannot reliably be erased securely by any means short of physical destruction (e.g., incineration). The key material must be securely

disposed of after use, to ensure the key material is never reused and to protect the messages sent. Because the key material must be transported from one endpoint to another, and persist until the message is sent or received, it can be more

vulnerable to forensic recovery than the transient plaintext it protects.