Domain 3

Question 1

Which of these is TRUE about 3DES K1?

Answer 1

It is a 64-bit block cipher with a 112-bit key strength.

Question 2

When we are talking about the Twofish encryption algorithm, which of these is TRUE?

Answer 2

It is a 128-bit block cipher with 128, 192 or 256-bit keys.

Question 3

We are talking about implementing new encryption in our organization. Which of these would be TRUE about IDEA?

Answer 3

IDEA (International Data Encryption Algorithm): Designed to replace DES. Symmetric, 128 bit key, 64 bit block size, considered safe. Not widely used now, since it is patented and slower than AES.

Question 4

We are looking at implementing a new type of symmetric encryption. Which of these symmetric encryption types are no longer considered secure, and should be something we should NOT consider?

Answer 4

RC4: Used by WEP/WPA/SSL/TLS. Pseudorandom keystream. No longer considered secure. Symmetric, Stream cipher, 40-2048 bit key length.

Question 5

If we have 100 users in our organization that are all needing to communicate securely with each other, would symmetric or asymmetric encryption use the highest number of encryption keys?

Answer 5

Symmetric would use 4950 keys (100x(100-1))/2, asymmetric uses 2 keys per person so 200 keys.

Question 6

If we are using Mandatory Access Control (MAC) and we are looking at the BIBA’s * integrity axiom, what can’t we do?

Answer 6

Write up.
BIBA: Integrity (Mandatory Access Control): * Integrity Axiom : “No Write UP”. Subjects with Secret clearance can’t write Secret information to Top Secret folders. We don’t want wrong or lacking lower level information to propagate to a higher level.

Question 7

Which of these symmetric encryption types are no longer considered secure?

Answer 7

3DES K3

3DES (Triple DES) K3 (keymode3) – Same key 3 times, just as insecure as DES (encrypt/decrypt/encrypt).

Question 8

What is happening when a brownout occurs?

Answer 8

We have a long low voltage period.

Question 9

Which of these is a type of asymmetric encryption?

Answer 9

RSA

RSA is asymmetric. 3DES, RC6 and Twofish are all symmetric forms of encryption.

Question 10

The order of the plaintext should be dispersed in the ciphertext. What is this called?

Answer 10

Diffusion

Diffusion is how the order of the plaintext should be “diffused” (dispersed) in the ciphertext.

Question 11

What is the relationship between plaintext and ciphertext is called?

Answer 11

Confusion

Confusion is the relationship between the plaintext and ciphertext; it should be as random (confusing) as possible.

Question 12

BIBA’s Invocation Property prohibits users from what?

Answer 12

No read and write up.

Invocation Property: “No Read or Write UP”. Subjects can never access or alter data on a higher level.

Question 13

Which is the MOST secure encryption type of these 4?

• DES
• Blowfish
• AES
• RC4

Answer 13

AES

DES, Blowfish and RC4 are no longer considered secure, AES is still considered secure.

Question 14

Which of these is a TRUE about hybrid encryption?

Answer 14

It uses private and public keys to share a symmetric session key.

Question 15

When a CPU can execute multiple processes concurrently, it is called what?

• multithreading
• multiprocessing
• multitasking

Answer 15

Multithreading

Multithreading is the ability of a central processing unit (CPU) or a single core in a multi-core processor to execute multiple processes or threads concurrently, appropriately supported by the operating system.

Question 16

Which historical type of encryption involved the sender switching letters a certain number of spots forwards or back in the alphabet, with the receiver doing the same in the opposite direction?

Answer 16

Caesar Cipher (Substitution) - Done by switching letters a certain numbers of spots in the alphabet. “Pass the exam” moved 3 back would be “Mxpp qeb buxj.”

Question 17

When we are rearranging the plaintext what is it called?

Answer 17

Permutation (transposition) provides confusion by rearranging the characters of the plaintext.

Question 18

Which of these are functions the CPU performs? (Select all that apply).

Answer 18

CPU (Central Processing Unit), uses Fetch, Decode, Execute, and Store. Fetch - Gets the instructions from memory into the processor. Decode - Internally decodes what it is instructed to do. Execute - Takes the add or subtract values from the registers. Store - Stores the result back into another register (retiring the instruction). Pipelining – Combining multiple steps into one process; can Fetch, Decode, Execute, Store in same clock cycle.

Question 19

Which of these would be a TRUE statement about symmetric encryption?

Answer 19

It is the strongest per bit.

Asymmetric vs Symmetric Encryption and Hybrid: Asymmetric Pros: It does not need a pre-shared key, only 2x users = total keys. Cons: It is much slower, it is weaker per bit. Symmetric: Pros: Much faster, stronger per bit. Cons: Needs a pre-shared key, n(n-1)/2 users, becomes unmanageable with many users.

Question 20

A historical type of encryption that was based on a set of disks with random letters; the sender and receiver would agree on the disk order. What is it called?

Answer 20

Bazeries.

The Jefferson Disk (Bazeries Cylinder) - is a cipher system using a set of wheels or disks, each with the 26 letters of the alphabet arranged around the edge. Jefferson (US president) invented it, and Bazeries improved it. The order of the letters is different for each disk and is usually scrambled in some random way. Each disk is marked with a unique number. A hole in the center of the disks allows them to be stacked on an axle. The disks are removable and can be mounted on the axle in any order desired. The order of the disks is the cipher key, and both sender and receiver must arrange the disks in the same predefined order. Jefferson’s device had 36 disks.

Question 21

Which of these rotary based encryption machines was NOT known to have been broken while it was in active use?

Answer 21

SIGABA.

SIGABA: A rotor machine used by the United States throughout World War II and into the 1950s, similar to the Enigma. It was more complex, and was built after examining the weaknesses of the Enigma. No successful cryptanalysis of the machine during its service lifetime is publicly known. It used 3x 5 sets of rotors.

Question 22

Prime number factorization is an example of what?

Answer 22

One way functions.
Prime Number Factorization: Factoring large Prime numbers using a one-way factorization - It is easy to multiply 2 numbers, but hard to discern the 2 numbers multiplied from the result.

Question 23

What historical encryption was written on a thin piece of parchment that was wrapped around a round stick of a certain diameter?

Answer 23

Spartan Scytale.

Spartan Scytale - Message written lengthwise on a long thin piece of parchment wrapped around a certain size round stick. By itself it would make no sense, but if rewrapped around a stick of the same diameter it would be decipherable.

Question 24

Which of these are types of symmetric encryption? (Select all that apply).
A. Diffie-Hellman (DH)
B. Twofish
C. Advanced Encryption Standard (AES)
D. Data Encryption Standard (DES)
C. Elliptic Curve Cryptography ECC

Answer 24

Twofish
AES
DES

Question 25

After the Second World War the US designed and built the SIGABA. How many rotors did it use?

Answer 25

15 A rotor machine used by the United States throughout World War II and into the 1950s, similar to the Enigma. It was more complex, and was built after examining the weaknesses of the Enigma. No successful cryptanalysis of the machine during its service lifetime is publicly known. It used 3x 5 sets of rotors.

Question 26

What handles all access between objects and subjects in the computer kernel?

Answer 26

Reference monitor. The Kernel At the core of the OS is the Kernel. At ring 0 (or 3), it interfaces between the operating system (and applications) and the hardware. Microkernels are modular kernels. The reference monitor is a core function of the kernel; it handles all access between subjects and objects. It is always on and can't be bypassed.

Question 27

Which type of fire extinguisher would you use on a metal fire?

Answer 27

Dry powder.

Question 28

If we want to implement a type of encryption that uses discrete logarithms, which of these could we choose?

Answer 28

Elliptic Curve Cryptography (ECC) is a one-way function that uses discrete Logarithms applied to elliptical curves. Much stronger per bit than normal discrete Logarithms.