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

EC-COUNCIL 212-81 Online Questions & Answers

• Question 131:

  Which of the following asymmetric algorithms is described by U.S. Patent 5,231,668 and FIPS 186

  A. AES
  B. RC4
  C. DSA
  D. RSA
  C. DSA

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  Explanation

  DSA https://ru.wikipedia.org/wiki/DSA The National Institute of Standards and Technology (NIST) proposed DSA for use in their Digital Signature Standard (DSS) in 1991, and adopted it as FIPS 186 in 1994. DSA is covered by U.S. Patent 5,231,668 , filed July 26, 1991 and now expired, and attributed to David W. Kravitz, a former NSA employee.

• Question 132:

  Which of the following would be the fastest.

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

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  Explanation

  AES https://en.wikipedia.org/wiki/Symmetric-key_algorithm AES - symmetric cipher. Symmetric keys use the same key for both encryption and decryption. Both the sender and receiver of the data must know and share the secret key. For standard encrypt/decrypt functions, symmetric algorithms generally perform much faster than their asymmetrical counterparts. This is due to the fact that asymmetric cryptography is massively inefficient. Symmetric cryptography is designed precisely for the efficient processing of large volumes of data. In other words, symmetric encryption is generally used for speed and performance, e.g. when there's a large amount of data that needs to be encrypted/protected.

• Question 133:

  Which of the following is a type of encryption that has two different keys. One key can encrypt the message and the other key can only decrypt it?

  A. Block cipher
  B. Asymmetric
  C. Symmetric
  D. Stream cipher
  B. Asymmetric

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  Explanation

  Asymmetric Public-key cryptography, or asymmetric cryptography, is a cryptographic system that uses pairs of keys: public keys, which may be disseminated widely, and private keys, which are known only to the owner. The generation of such keys depends on cryptographic algorithms based on mathematical problems to produce one-way functions. Effective security only requires keeping the private key private; the public key can be openly distributed without compromising security.

• Question 134:

  The 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.

  A. Cipher-block chaining (CBC)
  B. Electronic codebook (ECB)
  C. Output feedback (OFB)
  D. Cipher feedback (CFB)
  C. Output feedback (OFB)

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  Explanation

  Output feedback (OFB)

  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.

• Question 135:

  With Cipher-block chaining (CBC) what happens?

  A. The block cipher is turned into a stream cipher
  B. The message is divided into blocks and each block is encrypted separately. This is the most basic mode for symmetric encryption
  C. Each block of plaintext is XORed with the previous ciphertext block before being encrypted
  D. The cipher text from the current round is XORed with the plaintext for the next round
  C. Each block of plaintext is XORed with the previous ciphertext block before being encrypted

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  Explanation

  Each block of plaintext is XORed with the previous ciphertext block before being encrypted https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher_block_chaining_(CB C)

  In CBC mode, each block of plaintext is XORed with the previous ciphertext block before being encrypted. This way, each ciphertext block depends on all plaintext blocks processed up to that point. To make each message unique, an

  initialization vector must be used in the first block.

• Question 136:

  What is a "Collision attack" in cryptography?

  A. Collision attacks try to break the hash into three parts to get the plaintext value
  B. Collision attacks try to get the public key
  C. Collision attacks try to break the hash into two parts, with the same bytes in each part to get the private key
  D. Collision attacks try to find two inputs producing the same
  D. Collision attacks try to find two inputs producing the same

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  Explanation

  Collision attacks try to find two inputs producing the same https://en.wikipedia.org/wiki/Collision_attack

  A collision attack on a cryptographic hash tries to find two inputs producing the same hash value, i.e. a hash collision. This is in contrast to a preimage attack where a specific target hash value is specified.

• Question 137:

  You are explaining basic mathematics to beginning cryptography students. You are covering the basic math used in RSA. A prime number is defined as

  A. Odd numbers with no divisors
  B. Odd numbers
  C. Any number only divisible by odd numbers
  D. Any number only divisible by one and itself
  C. Any number only divisible by odd numbers

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  Explanation

  Any number only divisible by one and itself https://en.wikipedia.org/wiki/Prime_number A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways of writing it as a product, 1 ?5 or 5 ?1, involve 5 itself. However, 4 is composite because it is a product (2 ?2) in which both numbers are smaller than 4. Primes are central in number theory because of the fundamental theorem of arithmetic: every natural number greater than 1 is either a prime itself or can be factorized as a product of primes that is unique up to their order.

• Question 138:

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

  A. 10111010
  B. 10101010
  C. 11101101
  D. 00010010
  D. 00010010

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  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

• Question 139:

  Calculates the average LSB and builds a table of frequencies and Pair of Values. Performs a test on the two tables. It measures the theoretical vs. calculated population difference.

  A. Certificate Authority
  B. Raw Quick Pair
  C. Chi-Square Analysis
  D. SP network
  C. Chi-Square Analysis

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  Explanation

  Chi-Square Analysis https://en.wikipedia.org/wiki/Chi-squared_test A chi-squared test, is a statistical hypothesis test that is valid to perform when the test statistic is chi-squared distributed under the null hypothesis, specifically Pearson's chi- squared test and variants thereof. Pearson's chi-squared test is used to determine whether there is a statistically significant difference between the expected frequencies and the observed frequencies in one or more categories of a contingency table. In cryptanalysis, the chi-squared test is used to compare the distribution of plaintext and (possibly) decrypted ciphertext. The lowest value of the test means that the decryption was successful with high probability. This method can be generalized for solving modern cryptographic problems.

• Question 140:

  Manipulating individuals so that they will divulge confidential information, rather than by breaking in or using technical cracking techniques.

  A. Linear cryptanalysis
  B. Replay attack
  C. Side-channel attack
  D. Social engineering attack
  D. Social engineering attack

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  Explanation

  Social engineering attack https://en.wikipedia.org/wiki/Social_engineering_(security) Social engineering is the psychological manipulation of people into performing actions or divulging confidential information. This differs from social engineering within the social sciences, which does not concern the divulging of confidential information. A type of confidence trick for the purpose of information gathering, fraud, or system access, it differs from a traditional "con" in that it is often one of many steps in a more complex fraud scheme.