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

EC-COUNCIL 212-81 Online Questions & Answers

• Question 1:

  An attack that is particularly successful against block ciphers based on substitution- permutation networks. For a block size b, holds b-k bits constant and runs the other k through all 2k possibilities. For k=1, this is just deferential cryptanalysis, but with k>1 it is a new technique.

  A. Differential Cryptanalysis
  B. Linear Cryptanalysis
  C. Chosen Plaintext Attack
  D. Integral Cryptanalysis
  D. Integral Cryptanalysis

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  explanation:

  Explanation

  Integral Cryptanalysis https://en.wikipedia.org/wiki/Integral_cryptanalysis Integral cryptanalysis is a cryptanalytic attack that is particularly applicable to block ciphers based on substitution-permutation networks. It was originally designed by Lars Knudsen as a dedicated attack against Square, so it is commonly known as the Square attack. It was also extended to a few other ciphers related to Square: CRYPTON, Rijndael, and SHARK. Stefan Lucks generalized the attack to what he called a saturation attack and used it to attack Twofish, which is not at all similar to Square, having a radically different Feistel network structure. Forms of integral cryptanalysis have since been applied to a variety of ciphers, including Hierocrypt, IDEA, Camellia, Skipjack, MISTY1, MISTY2, SAFER++, KHAZAD, and FOX (now called IDEA NXT).

• Question 2:

  A _____ is a function is not reversible.

  A. Stream cipher
  B. Asymmetric cipher
  C. Hash
  D. Block Cipher
  C. Hash

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  explanation:

  Explanation

  Hash https://en.wikipedia.org/wiki/Hash_function Hash functions are irreversible. This is actually required for them to fulfill their function of determining whether someone possesses an uncorrupted copy of the hashed data. This brings susceptibility to brute force attacks, which are quite powerful these days, particularly against MD5.

• Question 3:

  What size key does Skipjack use?

  A. 128 bit
  B. 56 bit
  C. 80 bit
  D. 256 bit
  C. 80 bit

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  explanation:

  Explanation

• Question 4:

  Created in 1977 by Ron Rivest, Adi Shamir, and Leonard Adleman at MIT. Most widely used public key cryptography algorithm. Based on relationships with prime numbers. This algorithm is secure because it is difficult to factor a large integer composed of two or more large prime factors.

  A. PKI
  B. DES
  C. RSA
  D. Diffie-Helmann
  C. RSA

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  explanation:

  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. 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.

• Question 5:

  With Electronic codebook (ECB) what happens:

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

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  explanation:

  Explanation

  The message is divided into blocks and each block is encrypted separately. This is the most basic mode for symmetric encryption

  https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Electronic_codebook_(ECB )

  The simplest of the encryption modes is the electronic codebook (ECB) mode (named after conventional physical codebooks). The message is divided into blocks, and each block is encrypted separately.

• Question 6:

  What is a variation of DES that uses a technique called Key Whitening?

  A. Blowfish
  B. DESX
  C. 3DES
  D. AES
  B. DESX

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  explanation:

  Explanation

  DESX https://en.wikipedia.org/wiki/DES-X In cryptography, DES-X (or DESX) is a variant on the DES (Data Encryption Standard) symmetric-key block cipher intended to increase the complexity of a brute-force attack using a technique called key whitening.

• Question 7:

  Encryption of the same plain text with the same key results in the same cipher text. Use of an IV that is XORed with the first block of plain text solves this problem.

  A. CFB
  B. GOST
  C. ECB
  D. RC4
  C. ECB

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  explanation:

  Explanation

  ECB https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation The simplest of the encryption modes is the electronic codebook (ECB) mode (named after conventional physical codebooks). The message is divided into blocks, and each block is encrypted separately. The disadvantage of this method is a lack of diffusion. Because ECB encrypts identical plaintext blocks into identical ciphertext blocks, it does not hide data patterns well. ECB is not recommended for use in cryptographic protocols. ECB mode can also make protocols without integrity protection even more susceptible to replay attacks, since each block gets decrypted in exactly the same way.

• Question 8:

  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:

  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 9:

  Hash. Created by Ronald Rivest. Replaced MD4. 128 bit output size, 512 bit block size, 32 bit word size, 64 rounds. Infamously compromised by Flame malware in 2012. A. Keccak

  B. MD5

  C. SHA-1

  D. TIGER

  Correct Answer. B
  B

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  explanation:

  Explanation

  MD5 https://en.wikipedia.org/wiki/MD5 The MD5 message-digest algorithm is a widely used hash function producing a 128-bit hash value. Although MD5 was initially designed to be used as a cryptographic hash function, it has been found to suffer from extensive vulnerabilities. It can still be used as a checksum to verify data integrity, but only against unintentional corruption. It remains suitable for other non-cryptographic purposes, for example for determining the partition for a particular key in a partitioned database. MD5 was designed by Ronald Rivest in 1991 to replace an earlier hash function MD4, and was specified in 1992 as RFC 1321

• Question 10:

  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:

  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.