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Free 212-81 Exam Braindumps (page: 22)

Page 21 of 50
PDF with 206 Questions

If you XOR 10111000 with 10101010, what is the result?

  1. 10111010
  2. 10101010
  3. 11101101
  4. 00010010

Answer(s): D

Explanation:

00010010
https://en.wikipedia.org/wiki/XOR_cipher
1 0 1 1 1 0 0 0
1 0 1 0 1 0 1 0
0 0 0 1 0 0 1 0



Which one of the following is a symmetric key system using 64-bit blocks?

  1. DES
  2. PGP
  3. DSA
  4. RSA

Answer(s): A

Explanation:

DES
https://en.wikipedia.org/wiki/Data_Encryption_Standard
DES is the archetypal block cipher—an algorithm that takes a fixed-length string of plaintext bits and transforms it through a series of complicated operations into another ciphertext bitstring of the same length. In the case of DES, the block size is 64 bits. DES also uses a key to customize the transformation, so that decryption can supposedly only be performed by those who know the particular key used to encrypt. The key ostensibly consists of 64 bits; however, only 56 of these are actually used by the algorithm. Eight bits are used solely for checking parity, and are thereafter discarded. Hence the effective key length is 56 bits.

Incorrect answers:
PGP - Pretty Good Privacy (PGP) is an encryption program that provides cryptographic privacy and authentication for data communication. PGP is used for signing, encrypting, and decrypting texts, e- mails, files, directories, and whole disk partitions and to increase the security of e-mail communications. Phil Zimmermann developed PGP in 1991.
RSA - RSA (Rivest–Shamir–Adleman) is a public-key cryptosystem that is widely used for secure data transmission. It is also one of the oldest. The acronym RSA comes from the surnames of Ron Rivest, Adi Shamir, and Leonard Adleman, who publicly described the algorithm in 1977. An equivalent system was developed secretly, in 1973 at GCHQ (the British signals intelligence agency), by the English mathematician Clifford Cocks. That system was declassified in 1997.
In a public-key cryptosystem, the encryption key is public and distinct from the decryption key, which is kept secret (private). An RSA user creates and publishes a public key based on two large prime numbers, along with an auxiliary value. The prime numbers are kept secret. Messages can be encrypted by anyone, via the public key, but can only be decoded by someone who knows the prime numbers.
DSA - The Digital Signature Algorithm (DSA) is a Federal Information Processing Standard for digital signatures, based on the mathematical concept of modular exponentiation and the discrete logarithm problem. DSA is a variant of the Schnorr and ElGamal signature schemes.



Ferris has been assigned the task of selecting security for his company's wireless network. It is important that he pick the strongest form of wireless security. Which one of the following is the strongest wireless security?

  1. WEP
  2. WPA
  3. WPA2
  4. TKIP

Answer(s): C

Explanation:

WPA2
https://en.wikipedia.org/wiki/Wi-Fi_Protected_Access
WPA (sometimes referred to as the draft IEEE 802.11i standard) became available in 2003. The Wi-Fi Alliance intended it as an intermediate measure in anticipation of the availability of the more secure and complex WPA2, which became available in 2004 and is a common shorthand for the full IEEE 802.11i (or IEEE 802.11i-2004) standard.



A non-secret binary vector used as the initializing input algorithm for encryption of a plaintext block sequence to increase security by introducing additional cryptographic variance.

  1. IV
  2. Salt
  3. L2TP
  4. Nonce

Answer(s): A

Explanation:

IV
https://en.wikipedia.org/wiki/Initialization_vector
In cryptography, an initialization vector (IV) or starting variable (SV) is a fixed-size input to a cryptographic primitive that is typically required to be random or pseudorandom. Randomization is crucial for encryption schemes to achieve semantic security, a property whereby repeated usage of the scheme under the same key does not allow an attacker to infer relationships between segments of the encrypted message. For block ciphers, the use of an IV is described by the modes of operation. Randomization is also required for other primitives, such as universal hash functions and message authentication codes based thereon.

Incorrect answers:
L2TP - PPTP combined with L2F (Layer 2 Forwarding) (Cisco proprietary protocol) - Uses EAP, CHAP, MS-CHAP, PAP, or S-PAP for authentication. IPSec is used to provide encryption.
Salt - random bits of data intermixed with the message that is to be hashed.
Nonce - an arbitrary number that can be used just once in a cryptographic communication. It is similar in spirit to a nonce word, hence the name. It is often a random or pseudo-random number issued in an authentication protocol to ensure that old communications cannot be reused in replay attacks. They can also be useful as initialization vectors and in cryptographic hash functions.






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