EC-COUNCIL 212-81 Online Practice Questions and Exam Preparation

EC-COUNCIL 212-81 Online Questions & Answers

• Question 31:

  Modern symmetric ciphers all make use of one or more s-boxes. Both Feistel and non- Feistel ciphers use these s-boxes. What is an s-box?

  A. A substitution box where input bits are replaced
  B. A black box for the algorithm implementation
  C. A shifting box where input bits are shifted
  D. Another name for the round function
  A. A substitution box where input bits are replaced

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  Explanation

  Substitution box where input bits are replaced https://en.wikipedia.org/wiki/S-box In cryptography, an S-box (substitution-box) is a basic component of symmetric key algorithms which performs substitution. In block ciphers, they are typically used to obscure the relationship between the key and the ciphertext -- Shannon's property of confusion.

• Question 32:

  How many qubits are needed to break RSA?

  A. 1000
  B. 2000
  C. 4000
  D. 100
  C. 4000

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  Explanation

• Question 33:

  A symmetric block cipher designed in 1993 by Bruce Schneier. Was intended as a replacement for DES. Like DES it is a 16 round Feistel working on 64bit blocks. Can have bit sizes 32bits to 448bits.

  A. Skipjack
  B. Blowfish
  C. MD5
  D. Serpent
  B. Blowfish

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  Explanation

  Blowfish https://en.wikipedia.org/wiki/Blowfish_(cipher) Blowfish is a symmetric-key block cipher, designed in 1993 by Bruce Schneier and included in many cipher suites and encryption products. Blowfish provides a good encryption rate in software and no effective cryptanalysis of it has been found to date. However, the Advanced Encryption Standard (AES) now receives more attention, and Schneier recommends Twofish for modern applications. Blowfish has a 64-bit block size and a variable key length from 32 bits up to 448 bits. It is a 16-round Feistel cipher and uses large key-dependent S-boxes.

• Question 34:

  An authentication method that periodically re-authenticates the client by establishing a hash that is then resent from the client is called ______.

  A. CHAP
  B. SPAP
  C. PAP
  D. EAP
  A. CHAP

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  Explanation

  CHAP https://en.wikipedia.org/wiki/Challenge-Handshake_Authentication_Protocol Challenge-Handshake Authentication Protocol (CHAP) is an identity verification protocol that does not rely on sending a shared secret between the access-requesting party and the identity-verifying party (the authenticator). CHAP is based on a shared secret, but in order to authenticate, the authenticator sends a "challenge" message to the access-requesting party, which responds with a value calculated using a "one-way hash" function that takes as inputs the challenge and the shared secret. The authenticator checks the response against its own calculation of the expected hash value. If the values match, the authentication succeeds, otherwise it fails. Following the establishment of an authenticated connection, the authenticator may send a challenge to the access-requesting party at random intervals, to which the access-requesting party will have to produce the correct response.

• Question 35:

  What is the largest key size that AES can use?

  A. 256
  B. 56
  C. 512
  D. 128
  A. 256

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  Explanation

  https://en.wikipedia.org/wiki/Advanced_Encryption_Standard For AES, NIST selected three members of the Rijndael family, each with a block size of 128 bits, but three different key lengths: 128, 192 and 256 bits.

• Question 36:

  WPA2 uses AES for wireless data encryption at which of the following encryption levels?

  A. 128 bit and CRC
  B. 128 bi and TKIP
  C. 128 bit and CCMP
  D. 64 bit and CCMP
  C. 128 bit and CCMP

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  Explanation

  128 bit and CCMP

  Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (CCMP) is an encryption protocol that forms part of the 802.11i standard for wireless local area networks (WLANs), particularly those using WiMax technology.

  CCMP employs 128-bit keys and a 48-bit initialization vector that minimizes vulnerability to replay attacks.

• Question 37:

  Which component of IPsec performs protocol-level functions that are required to encrypt and decrypt the packets?

  A. IPsec Policy Agent
  B. Internet Key Exchange (IKE)
  C. Oakley
  D. IPsec driver
  B. Internet Key Exchange (IKE)

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  Explanation

  Internet Key Exchange (IKE)

  https://en.wikipedia.org/wiki/Internet_Key_Exchange Internet Key Exchange (IKE, sometimes IKEv1 or IKEv2, depending on version) is the protocol used to set up a security association (SA) in the IPsec protocol suite. IKE builds upon the

  Oakley protocol and ISAKMP. IKE uses X.509 certificates for authentication either pre-shared or distributed using DNS (preferably with DNSSEC) and a Diffie璈ellman key exchange to set up a shared session secret from which cryptographic

  keys are derived.

• Question 38:

  What is the solution to the equation 8 mod 3?

  A. 1
  B. 4
  C. 3
  D. 2
  D. 2

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  Explanation

  https://en.wikipedia.org/wiki/Modulo_operation The modulo operation returns the remainder or signed remainder of a division, after one number is divided by another (called the modulus of the operation). Given two positive numbers a and n, a modulo n (abbreviated as a mod n) is the remainder of the Euclidean division of a by n, where a is the dividend and n is the divisor. The modulo operation is to be distinguished from the symbol mod, which refers to the modulus (or divisor) one is operating from. For example, the expression "5 mod 2" would evaluate to 1, because 5 divided by 2 has a quotient of 2 and a remainder of 1, while "9 mod 3" would evaluate to 0, because the division of 9 by 3 has a quotient of 3 and a remainder of 0; there is nothing to subtract from 9 after multiplying 3 times 3.

• Question 39:

  Electromechanical rotor-based cipher used in World War II

  A. ROT13 Cipher
  B. Cipher Disk
  C. Enigma Machine
  D. Rail Fence Cipher
  C. Enigma Machine

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  Explanation

  Enigma Machine https://en.wikipedia.org/wiki/Enigma_machine The Enigma machine is an encryption device developed and used in the early- to mid-20th century to protect commercial, diplomatic and military communication. It was employed extensively by Nazi Germany during World War II, in all branches of the German military. Enigma has an electromechanical rotor mechanism that scrambles the 26 letters of the alphabet.

• Question 40:

  What does Output feedback (OFB) do:

  A. The message is divided into blocks and each block is encrypted separately. This is the most basic mode for symmetric encryption
  B. The cipher text from the current round is XORed with the plaintext from the previous round
  C. A block cipher is converted into a stream cipher by generating a keystream blocks, which are then XORed with the plaintext blocks to get the ciphertext
  D. The cipher text from the current round is XORed with the plaintext for the next round
  C. A block cipher is converted into a stream cipher by generating a keystream blocks, which are then XORed with the plaintext blocks to get the ciphertext

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  Explanation

  A block cipher is converted into a stream cipher by generating a keystream blocks, which are then XORed with the plaintext blocks to get the ciphertext https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Output_feedback_(OFB) The output feedback (OFB) mode makes a block cipher into a synchronous stream cipher. It generates keystream blocks, which are then XORed with the plaintext blocks to get the ciphertext. Just as with other stream ciphers, flipping a bit in the ciphertext produces a flipped bit in the plaintext at the same location. This property allows many error-correcting codes to function normally even when applied before encryption.