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

EC-COUNCIL 212-81 Online Questions & Answers

• Question 41:

  What size block does Skipjack use?

  A. 64
  B. 512
  C. 128
  D. 256
  A. 64

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  Explanation

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

  Skipjack uses an 80-bit key to encrypt or decrypt 64-bit data blocks. It is an unbalanced Feistel network with 32 rounds.

• Question 42:

  Denis is looking at an older system that uses DES encryption. A colleague has told him that DES is insecure due to a small key size. What is the key length used for DES?

  A. 128
  B. 256
  C. 56
  D. 64
  C. 56

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  Explanation

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

  The Data Encryption Standard is a symmetric-key algorithm for the encryption of digital data. Although its short key length of 56 bits makes it too insecure for applications, it has been highly influential in the advancement of cryptography.

• Question 43:

  What is the formula m^e %n related to?

  A. Encrypting with EC
  B. Decrypting with RSA
  C. Generating Mersenne primes
  D. Encrypting with RSA
  D. Encrypting with RSA

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  Explanation

  Encrypting with RSA

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

  RSA Encrypting a message m (number) with the public key (n, e) is calculated:

  M' := m^e %n

• Question 44:

  If you wished to see a list of revoked certificates from a CA, where would you look?

  A. RA
  B. RFC
  C. CRL
  D. CA
  C. CRL

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  Explanation

  CRL https://ru.wikipedia.org/wiki/Certificate_Revocation_List Certificate Revocation List (or CRL) is "a list of digital certificates that have been revoked by the issuing certificate authority (CA) before their scheduled expiration date and should no longer be trusted".

• Question 45:

  Cryptographic hashes are often used for message integrity and password storage. It is important to understand the common properties of all cryptographic hashes. What is not true about a hash?

  A. Few collisions
  B. Reversible
  C. Variable length input
  D. Fixed length output
  B. Reversible

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  Explanation

  Reversible https://en.wikipedia.org/wiki/Hash_function Hash functions are not reversible.

• Question 46:

  Bob's password is hashed, and so is John's. Even though they used different passwords, the hash is the same. What is this called?

  A. A collision
  B. A mistake
  C. Convergence
  D. Transposition
  A. A collision

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  Explanation

  A collision

  https://en.wikipedia.org/wiki/Collision_(computer_science) A collision or clash is a situation that occurs when two distinct pieces of data have the same hash value, checksum, fingerprint, or cryptographic digest.

• Question 47:

  A list of certificates that have been revoked.

  A. CA
  B. CRL
  C. PCBC
  D. OCSP
  B. CRL

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  Explanation

  CRL https://en.wikipedia.org/wiki/Certificate_revocation_list In cryptography, a certificate revocation list (or CRL) is "a list of digital certificates that have been revoked by the issuing certificate authority (CA) before their scheduled expiration date and should no longer be trusted".

• Question 48:

  Which of the following is generally true about key sizes?

  A. Larger key sizes increase security
  B. Key size is irrelevant to security
  C. Key sizes must be more than 256 bits to be secure
  D. Smaller key sizes increase security
  A. Larger key sizes increase security

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  Explanation

  Larger key sizes increase security https://en.wikipedia.org/wiki/Key_size Key length defines the upper-bound on an algorithm's security (i.e. a logarithmic measure of the fastest known attack against an algorithm), since the security of all algorithms can be violated by brute-force attacks. Ideally, the lower-bound on an algorithm's security is by design equal to the key length (that is, the security is determined entirely by the keylength, or in other words, the algorithm's design doesn't detract from the degree of security inherent in the key length). Indeed, most symmetric-key algorithms are designed to have security equal to their key length. However, after design, a new attack might be discovered. For instance, Triple DES was designed to have a 168 bit key, but an attack of complexity 2112 is now known (i.e. Triple DES now only has 112 bits of security, and of the 168 bits in the key the attack has rendered 56 'ineffective' towards security). Nevertheless, as long as the security (understood as 'the amount of effort it would take to gain access') is sufficient for a particular application, then it doesn't matter if key length and security coincide. This is important for asymmetric-key algorithms, because no such algorithm is known to satisfy this property; elliptic curve cryptography comes the closest with an effective security of roughly half its key length.

• Question 49:

  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

  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 50:

  In relationship to hashing, the term _____refers to random bits that are used as one of the inputs to the hash. Essentially the ______ is intermixed with the message that is to be hashed

  A. Vector
  B. Salt
  C. Stream
  D. IV
  B. Salt

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  Explanation

  Salt

  https://en.wikipedia.org/wiki/Salt_(cryptography)

  A salt is random data that is used as an additional input to a one-way function that hashes data, a password or passphrase. Salts are used to safeguard passwords in storage. Historically a password was stored in plaintext on a system, but

  over time additional safeguards were developed to protect a user's password against being read from the system. A salt is one of those methods.