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

EC-COUNCIL 212-81 Online Questions & Answers

• Question 111:

  Which one of the following are characteristics of a hash function? (Choose two)

  A. Requires a key
  B. One-way
  C. Fixed length output
  D. Symmetric
  E. Fast
  B. One-way
  C. Fixed length output

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  Explanation

  Correct answers: One-way, Fixed length output https://en.wikipedia.org/wiki/Cryptographic_hash_function A cryptographic hash function is a mathematical algorithm that maps data of arbitrary size (often called the "message") to a bit array of a fixed size (the "hash value", "hash", or "message digest"). It is a one-way function, that is, a function which is practically infeasible to invert.

• Question 112:

  Nicholas is working at a bank in Germany. He is looking at German standards for pseudo random number generators. He wants a good PRNG for generating symmetric keys. The German Federal Office for Information Security (BSI) has established four criteria for quality of random number generators. Which ones can be used for cryptography?

  A. K4
  B. K5
  C. K3
  D. K2
  E. K1
  A. K4
  C. K3

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  Explanation

  K3 and K4 https://en.wikipedia.org/wiki/Pseudorandom_number_generator The German Federal Office for Information Security (Bundesamt f黵 Sicherheit in der Informationstechnik, BSI) has established four criteria for quality of deterministic random number generators.They are summarized here: K1 ?There should be a high probability that generated sequences of random numbers are different from each other. K2 ?A sequence of numbers is indistinguishable from";truly rando"; numbers according to specified statistical tests. The tests are the monobit test (equal numbers of ones and zeros in the sequence), poker test (a special instance of the chi-squared test), runs test (counts the frequency of runs of various lengths), longruns test (checks whether there exists any run of length 34 or greater in 20 000 bits of the sequence)--both from BSI and NIST, and the autocorrelation test. In essence, these requirements are a test of how well a bit sequence: has zeros and ones equally often; after a sequence of n zeros (or ones), the next bit a one (or zero) with probability one-half; and any selected subsequence contains no information about the next element(s) in the sequence. K3 ?It should be impossible for an attacker (for all practical purposes) to calculate, or otherwise guess, from any given subsequence, any previous or future values in the sequence, nor any inner state of the generator. K4 ?It should be impossible, for all practical purposes, for an attacker to calculate, or guess from an inner state of the generator, any previous numbers in the sequence or any previous inner generator states. For cryptographic applications, only generators meeting the K3 or K4 standards are acceptable.

• Question 113:

  A cipher is defined as what

  A. The algorithm(s) needed to encrypt and decrypt a message
  B. Encrypted text
  C. The key used to encrypt a message
  D. Any algorithm used in cryptography
  A. The algorithm(s) needed to encrypt and decrypt a message

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  Explanation

  The algorithm(s) needed to encrypt and decrypt a message https://en.wikipedia.org/wiki/Cipher In cryptography, a cipher (or cypher) is an algorithm for performing encryption or decryption--a series of well-defined steps that can be followed as a procedure. An alternative, less common term is encipherment. To encipher or encode is to convert information into cipher or code. In common parlance, "cipher" is synonymous with "code", as they are both a set of steps that encrypt a message; however, the concepts are distinct in cryptography, especially classical cryptography.

• Question 114:

  Which of the following areas is considered a strength of symmetric key cryptography when compared with asymmetric algorithms?

  A. Key distribution
  B. Security
  C. Scalability
  D. Speed
  D. Speed

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  Explanation

  Speed

  Symmetric key systems are considerably faster than asymmetric key systems but have issues with proper key distribution, controlling keys as more users need to communicate, and cannot provide non-repudiation or authenticity.

• Question 115:

  The Clipper chip is notable in the history of cryptography for many reasons. First, it was designed for civilian used secure phones. Secondly, it was designed to use a very specific symmetric cipher. Which one of the following was originally designed to provide built-in cryptography for the Clipper chip?

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

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  Explanation

  Skipjack https://en.wikipedia.org/wiki/Clipper_chip The Clipper chip was a chipset that was developed and promoted by the United States National Security Agency (NSA) as an encryption device that secured "voice and data messages" with a built-in backdoor that was intended to "allow Federal, State, and local law enforcement officials the ability to decode intercepted voice and data transmissions.". It was intended to be adopted by telecommunications companies for voice transmission. Introduced in 1993, it was entirely defunct by 1996. he Clipper chip used a data encryption algorithm called Skipjack to transmit information and the Diffie璈ellman key exchange-algorithm to distribute the cryptokeys between the peers. Skipjack was invented by the National Security Agency of the U.S. Government; this algorithm was initially classified SECRET, which prevented it from being subjected to peer review from the encryption research community. The government did state that it used an 80-bit key, that the algorithm was symmetric, and that it was similar to the DES algorithm. The Skipjack algorithm was declassified and published by the NSA on June 24, 1998. The initial cost of the chips was said to be $16 (unprogrammed) or $26 (programmed), with its logic designed by Mykotronx, and fabricated by VLSI Technology, Inc (see the VLSI logo on the image on this page).

• Question 116:

  You are studying classic ciphers. You have been examining the difference between single substitution and multi-substitution. Which one of the following is an example of a multi- alphabet cipher?

  A. Rot13
  B. Caesar
  C. Atbash
  D. Vigenère
  D. Vigenère

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  Explanation

  Vigenère https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher The Vigenère cipher is a method of encrypting alphabetic text by using a series of interwoven Caesar ciphers, based on the letters of a keyword. It employs a form of polyalphabetic substitution. First described by Giovan Battista Bellaso in 1553, the cipher is easy to understand and implement, but it resisted all attempts to break it until 1863, three centuries later. This earned it the description le chiffre indéchiffrable (French for 'the

  indecipherable cipher'). Many people have tried to implement encryption schemes that are essentially Vigenère ciphers. In 1863, Friedrich Kasiski was the first to publish a general method of deciphering Vigenère ciphers.

• Question 117:

  John works as a cryptography consultant. He finds that people often misunderstand the reality of breaking a cipher. What is the definition of breaking a cipher?

  A. Finding any method that is more efficient than brute force
  B. Uncovering the algorithm used
  C. Rendering the cypher no longer useable
  D. Decoding the key
  A. Finding any method that is more efficient than brute force

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  Explanation

  Finding any method that is more efficient than brute force.

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

  Bruce Schneier notes that even computationally impractical attacks can be considered breaks: "Breaking a cipher simply means finding a weakness in the cipher that can be exploited with a complexity less than brute force. Never mind that

  brute-force might require 2^128 encryptions; an attack requiring 2^110 encryptions would be considered a break...simply put, a break can just be a certificational weakness: evidence that the cipher does not perform as advertised."

• Question 118:

  Frank is trying to break into an encrypted file... He is attempting all the possible keys that could be used for this algorithm. Attempting to crack encryption by simply trying as many randomly generated keys as possible is referred to as what?

  A. Rainbow table
  B. Frequency analysis
  C. Brute force
  D. Kasiski
  C. Brute force

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  Explanation

  Brute force

  https://en.wikipedia.org/wiki/Brute-force_attack

  Brute-force attack consists of an attacker submitting many passwords or passphrases with the hope of eventually guessing correctly. The attacker systematically checks all possible passwords and passphrases until the correct one is found.

  Alternatively, the attacker can attempt to guess the key which is typically created from the password using a key derivation function. This is known as an exhaustive key search.

• Question 119:

  Asymmetric encryption method developed in 1984. It is used in PGP implementations and GNU Privacy Guard Software. Consists of 3 parts: key generator, encryption algorithm, and decryption algorithm.

  A. Tiger
  B. GOST
  C. RIPEMD
  D. ElGamal
  D. ElGamal

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  Explanation

  ElGamal https://en.wikipedia.org/wiki/ElGamal_encryption the ElGamal encryption system is an asymmetric key encryption algorithm for public-key cryptography which is based on the Diffie璈ellman key exchange. It was described by Taher Elgamal in 1985. ElGamal encryption is used in the free GNU Privacy Guard software, recent versions of PGP, and other cryptosystems. The Digital Signature Algorithm (DSA) is a variant of the ElGamal signature scheme, which should not be confused with ElGamal encryption.

• Question 120:

  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?

  A. WEP
  B. WPA
  C. WPA2
  D. TKIP
  C. WPA2

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  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.