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Network Security FAQ: Cryptography

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Network Security FAQ: Cryptography

Q1. How many possible keys are there for an 8-bit key?
a. 8
b. 82
c. 28
d. 65,536

Answer: c. There are 8 bits in that key, and all those bits can have two different values. To calculate the possible keys, multiply 2 by 2 by 2one time for every bit, or 28.

Q2. Which type of cipher typically acts on small units of data?
a. Block cipher
b. Stream cipher

Answer: b. Stream ciphers encrypt the bits of the message one at a time, and block ciphers take a number of bits and encrypt them as a single unit.

Q3. What is the maximum key length available with 3DES?
a. 56 bits
b. 168 bits
c. 160 bits
d. 112 bits
e. 128 bits

Answer: b. The maximum key length available with 3DES is 168 bits.

Q4. The AES has a variable key length. True or False?

Answer: True. AES can use 128-, 192-, or 256-bit keys to encrypt data blocks.

Q5. The security of the Diffie-Hellman algorithm is based on which of the following?
a. The secrecy of public values
b. The extreme amount of time required to perform exponentiation
c. The difficulty of factoring large primes
d. The secrecy of g and p values

Answer: c. The security of the Diffie-Hellman algorithm is based on the difficulty of factoring large primes.

Q6. What is the length of MD5 output (hash)?
a. 64 bits
b. 128 bits
c. 160 bits
d. 168 bits
e. 256 bits

Answer: b. The length of MD5 output (hash) is 128 bits.

7. What is the length of SHA-1 output (hash)?
a. 64 bits
b. 128 bits
c. 160 bits
d. 168 bits
e. 256 bits

Answer: c. The length of SHA-1 output (hash) is 160 bits.

8. What is eavesdropping?
a. An intruder gains illegitimate access by posing as an individual who actually can access secured resources.
b. An intruder “sniffs” the data transmission between two parties during communications over a public medium.
c. An intruder interrupts a dialogue and modifies the data between the two parties. The intruder would take over the entire session in an extreme case.

Answer: b. Eavesdropping is when an intruder “sniffs” the data transmission between two parties during communications over a public medium.

Q9. Which protocols can be layered on top of SSL? (Multiple answers are possible.)
a. HTTP
b. OSPF
c. FTP
d. Telnet
e. TFTP

Answer: a, c, and d. HTTP, FTP, and Telnet can be layered on top of SSL.

Q10. Name the three primary security vulnerabilities for communication over a public network.

Answer: Identity theft, eavesdropping, and man-in-the-middle are the three primary security vulnerabilities for communication over a public network.