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

EC-COUNCIL 212-81 Online Questions & Answers

• Question 71:

  Algorithm that was chosen for the Data Encryption Standard, which was altered and renamed Data Encryption Algorithm.

  A. Blowfish
  B. Rijndael
  C. Lucifer
  D. El Gamal
  C. Lucifer

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  Explanation

  Lucifer

  https://en.wikipedia.org/wiki/Lucifer_(cipher)

  Lucifer was a direct precursor to the Data Encryption Standard. One version, alternatively named DTD-1.

• Question 72:

  A cryptanalysis success where the attacker discovers additional plain texts (or cipher texts) not previously known.

  A. Total Break
  B. Distinguishing Algorithm
  C. Instance Deduction
  D. Information Deduction
  C. Instance Deduction

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  Explanation

  Instance Deduction

  https://en.wikipedia.org/wiki/Cryptanalysis

  The results of cryptanalysis can also vary in usefulness. For example, cryptographer Lars Knudsen (1998) classified various types of attack on block ciphers according to the amount and quality of secret information that was discovered:

  Total break -- the attacker deduces the secret key. Global deduction -- the attacker discovers a functionally equivalent algorithm for encryption and decryption, but without learning the key. Instance (local) deduction -- the attacker discovers

  additional plaintexts (or ciphertexts) not previously known.

  Information deduction -- the attacker gains some Shannon information about plaintexts (or ciphertexts) not previously known.

  Distinguishing algorithm -- the attacker can distinguish the cipher from a random permutation.

• Question 73:

  This algorithm was published by the German engineering firm Seimans in 1993. It is a software based stream cipher using Lagged Fibonacci generator along with a concept borrowed from the shrinking generator ciphers.

  A. RC4
  B. Blowfish
  C. Twofish
  D. FISH
  D. FISH

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  Explanation

  FISH

  https://en.wikipedia.org/wiki/FISH_(cipher)

  The FISH (FIbonacci SHrinking) stream cipher is a fast software based stream cipher using Lagged Fibonacci generators, plus a concept from the shrinking generator cipher. It was published by Siemens in 1993. FISH is quite fast in software

  and has a huge key length. However, in the same paper where he proposed Pike, Ross Anderson showed that FISH can be broken with just a few thousand bits of known plaintext.

• Question 74:

  All of the following are key exchange protocols except for____

  A. MQV
  B. AES
  C. ECDH
  D. DH
  B. AES

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  Explanation

• Question 75:

  A type of frequency analysis used to attack polyalphabetic substitution ciphers. It's used to try to discover patterns and use that information to decrypt the cipher.

  A. Kasiski Method
  B. Birthday Attack
  C. Information Deduction
  D. Integral Cryptanalysis
  A. Kasiski Method

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  Explanation

  Kasiski Method https://en.wikipedia.org/wiki/Kasiski_examination In cryptanalysis, Kasiski examination (also referred to as Kasiski's test or Kasiski's method) is a method of attacking polyalphabetic substitution ciphers, such as the Vigen鑢e cipher. It was first published by Friedrich Kasiski in 1863, but seems to have been independently discovered by Charles Babbage as early as 1846.

• Question 76:

  What best describes the shifting of each letter a fixed number of spaces to the left or right?

  A. Single substitution
  B. Multi substitution
  C. XOR
  D. Bit shifting
  D. Bit shifting

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  Explanation

  Single substitution https://en.wikipedia.org/wiki/Substitution_cipher#Simple_substitution Substitution of single letters separately--simple substitution--can be demonstrated by writing out the alphabet in some order to represent the substitution. This is termed a substitution alphabet. The cipher alphabet may be shifted or reversed (creating the Caesar and Atbash ciphers, respectively) or scrambled in a more complex fashion, in which case it is called a mixed alphabet or deranged alphabet.

• Question 77:

  A simple algorithm that will take the initial key and from that generate a slightly different key each round.

  A. Key Schedule
  B. Feistel Network
  C. SHA-2
  D. Diffie-Helman
  A. Key Schedule

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  Explanation

  Key Schedule https://en.wikipedia.org/wiki/Key_schedule In cryptography, the so-called product ciphers are a certain kind of cipher, where the (de- )ciphering of data is typically done as an iteration of rounds. The setup for each round is generally the same, except for round-specific fixed values called a round constant, and round-specific data derived from the cipher key called a round key. A key schedule is an algorithm that calculates all the round keys from the key.

• Question 78:

  If the round function is a cryptographically secure pseudorandom function, then ___rounds is sufficient to make it a "strong" pseudorandom permutation.

  A. 15
  B. 16
  C. 3
  D. 4
  D. 4

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  Explanation

  https://en.wikipedia.org/wiki/Feistel_cipher

  Michael Luby and Charles Rackoff analyzed the Feistel cipher construction, and proved that if the round function is a cryptographically secure pseudorandom function, with Ki used as the seed, then 3 rounds are sufficient to make the block

  cipher a pseudorandom permutation, while 4 rounds are sufficient to make it a "strong" pseudorandom permutation (which means that it remains pseudorandom even to an adversary who gets oracle access to its inverse permutation).

  Because of this very important result of Luby and Rackoff, Feistel ciphers are sometimes called Luby璕ackoff block ciphers.

• Question 79:

  What is Kerchoff's principle?

  A. A minimum of 15 rounds is needed for a Feistel cipher to be secure
  B. Only the key needs to be secret, not the actual algorithm
  C. Both algorithm and key should be kept secret
  D. A minimum key size of 256 bits is necessary for security
  B. Only the key needs to be secret, not the actual algorithm

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  Explanation

  Only the key needs to be secret, not the actual algorithm https://en.wikipedia.org/wiki/Kerckhoffs%27s_principle Kerckhoffs's principle of cryptography was stated by Netherlands born cryptographer Auguste Kerckhoffs in the 19th century: A cryptosystem should be secure even if everything about the system, except the key, is public knowledge.

• Question 80:

  In 1977 researchers and MIT described what asymmetric algorithm?

  A. DH
  B. RSA
  C. AES
  D. EC
  B. RSA

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  Explanation

  RSA

  https://en.wikipedia.org/wiki/RSA_(cryptosystem)

  RSA (Rivest璖hamir瑼dleman) 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.