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

EC-COUNCIL 212-81 Online Questions & Answers

• Question 101:

  Which one of the following uses three different keys, all of the same size?

  A. 3DES
  B. AES
  C. RSA
  D. DES
  A. 3DES

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  Explanation

  3DES https://en.wikipedia.org/wiki/Triple_DES Triple DES (3DES or TDES), officially the Triple Data Encryption Algorithm (TDEA or Triple DEA), is a symmetric-key block cipher, which applies the DES cipher algorithm three times to each data block.

• Question 102:

  If Bob is using asymmetric cryptography and wants to send a message to Alice so that only she can decrypt it, what key should he use to encrypt the message?

  A. Alice's private key
  B. Bob's private key
  C. Alice's public key
  D. Bob's public key
  C. Alice's public key

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  Explanation

  Alice's public key https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange In asymmetric (public key) cryptography, both communicating parties (i.e. both Alice and Bob) have two keys of their own -- just to be clear, that's four keys total. Each party has their own public key, which they share with the world, and their own private key which they ... well, which they keep private, of course but, more than that, which they keep as a closely guarded secret. The magic of public key cryptography is that a message encrypted with the public key can only be decrypted with the private key. Alice will encrypt her message with Bob's public key, and even though Eve knows she used Bob's public key, and even though Eve knows Bob's public key herself, she is unable to decrypt the message. Only Bob, using his secret key, can decrypt the message ... assuming he's kept it secret, of course.

• Question 103:

  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

  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 104:

  A _____ is a function that takes a variable-size input m and returns a fixed-size string.

  A. Feistel
  B. Asymmetric cipher
  C. Symmetric cipher
  D. Hash
  D. Hash

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  Explanation

  Hash https://en.wikipedia.org/wiki/Hash_function A hash function is any function that can be used to map data of arbitrary size to fixed-size values.

• Question 105:

  Widely used, particularly with Microsoft operating systems. Created by MIT and derives its name from the mythical three headed dog. The is a great deal of verification for the tickets and the tickets expire quickly. Client authenticates to the Authentication Server once using a long term shared secret and receives back a Ticket-Granting Server. Client can reuse this ticket to get additional tickets without reusing the shared secret. These tickets are used to prove authentication to the Service Server.

  A. Diffie-Hellman
  B. Yarrow
  C. Kerberos
  D. ElGamal
  C. Kerberos

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  Explanation

  Kerberos https://en.wikipedia.org/wiki/Kerberos_(protocol) Kerberos is a computer-network authentication protocol that works on the basis of tickets to allow nodes communicating over a non-secure network to prove their identity to one another in a secure manner. The protocol was named after the character Kerberos (or Cerberus) from Greek mythology, the ferocious three-headed guard dog of Hades. Its designers aimed it primarily at a client璼erver model and it provides mutual authentication--both the user and the server verify each other's identity. Kerberos protocol messages are protected against eavesdropping and replay attacks. Kerberos builds on symmetric key cryptography and requires a trusted third party, and optionally may use public-key cryptography during certain phases of authentication. Kerberos uses UDP port 88 by default.

• Question 106:

  Hash algortihm created by the Russians. Produces a fixed length output of 256bits. Input message is broken up into 256 bit blocks. If block is less than 256 bits then it is padded with 0s.

  A. TIGER
  B. GOST
  C. BEAR
  D. FORK-256
  B. GOST

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  Explanation

  GOST https://en.wikipedia.org/wiki/GOST_(hash_function) The GOST hash function, defined in the standards GOST R 34.11-94 and GOST 34.311- 95 is a 256-bit cryptographic hash function. It was initially defined in the Russian national standard GOST R 34.11-94 Information Technology ?Cryptographic Information Security ?Hash Function. The equivalent standard used by other member-states of the CIS is GOST 34.311-95.

• Question 107:

  Which of the following is a fundamental principle of cryptography that holds that the algorithm can be publicly disclosed without damaging security?

  A. Vigenere's principle
  B. Shamir's principle
  C. Kerkchoff's principle
  D. Babbage's principle
  C. Kerkchoff's principle

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  Explanation

  Kerkchoff's principle https://en.wikipedia.org/wiki/Kerckhoffs%27s_principle Kerckhoffs's principle (also called Kerckhoffs's desideratum, assumption, axiom, doctrine or law) 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. Kerckhoffs's principle was reformulated (or possibly independently formulated) by American mathematician Claude Shannon as "the enemy knows the system", i.e., "one ought to design systems under the assumption that the enemy will immediately gain full familiarity with them". In that form, it is called Shannon's maxim. This concept is widely embraced by cryptographers, in contrast to "security through obscurity", which is not.

• Question 108:

  In a Feistel cipher, the two halves of the block are swapped in each round. What does this provide?

  A. Diffusion
  B. Confusion
  C. Avalanche
  D. Substitution
  C. Avalanche

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  Explanation

  Confusion https://en.wikipedia.org/wiki/Confusion_and_diffusion#Definition Confusion means that each binary digit (bit) of the ciphertext should depend on several parts of the key, obscuring the connections between the two. The property of confusion hides the relationship between the ciphertext and the key. This property makes it difficult to find the key from the ciphertext and if a single bit in a key is changed, the calculation of the values of most or all of the bits in the ciphertext will be affected. Confusion increases the ambiguity of ciphertext and it is used by both block and stream ciphers.

  Incorrect answer: Avalanche - The avalanche effect is the desirable property of cryptographic algorithms, typically block ciphers and cryptographic hash functions, wherein if an input is changed slightly (for example, flipping a single bit), the output changes significantly (e.g., half the output bits flip). In the case of high-quality block ciphers, such a small change in either the key or the plaintext should cause a drastic change in the ciphertext. The actual term was first used by Horst Feistel, although the concept dates back to at least Shannon's diffusion. Diffusion - Diffusion means that if we change a single bit of the plaintext, then (statistically) half of the bits in the ciphertext should change, and similarly, if we change one bit of the ciphertext, then approximately one half of the plaintext bits should change.[2] Since a bit can have only two states, when they are all re-evaluated and changed from one seemingly random position to another, half of the bits will have changed state. Substitution - Substitution technique is a classical encryption technique where the characters present in the original message are replaced by the other characters or numbers or by symbols.

• Question 109:

  You are explaining the details of the AES algorithm to cryptography students. You are discussing the derivation of the round keys from the shared symmetric key. The portion of AES where round keys are derived from the cipher key using Rijndael's key schedule is called what?

  A. The key expansion phase
  B. The round key phase
  C. The bit shifting phase
  D. The initial round
  A. The key expansion phase

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  Explanation

  The key expansion phase

  https://en.wikipedia.org/wiki/Advanced_Encryption_Standard KeyExpansion ?round keys are derived from the cipher key using the AES key schedule. AES requires a separate 128-bit round key block for each round plus one more.

• Question 110:

  3DES can best be classified as which one of the following?

  A. Digital signature
  B. Symmetric algorithm
  C. Asymmetric algorithm
  D. Hashing algorithm
  B. Symmetric algorithm

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  Explanation

  Symmetric algorithm

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

  Triple DES (3DES or TDES), officially the Triple Data Encryption Algorithm (TDEA or Triple DEA), is a symmetric-key block cipher, which applies the DES cipher algorithm three times to each data block. The Data Encryption Standard's (DES)

  56-bit key is no longer considered adequate in the face of modern cryptanalytic techniques and supercomputing power. However, an adapted version of DES, Triple DES (3DES), uses the same algorithm to produce a more secure encryption.