EC-COUNCIL EC-COUNCIL Certifications 212-81 Questions & Answers

• Question 11:

  This is a 128 bit hash that is specified by RFC 1321. It was designed by Ron Rivest in 1991 to replace an earlier hash function.

  A. SHA1

  B. SHA-256

  C. RSA

  D. MD5

  Correct Answer: D

  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 12:

  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)

  Correct Answer: C

  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 13:

  Which of the following is a protocol for exchanging keys?

  A. DH

  B. EC

  C. AES

  D. RSA

  Correct Answer: A

  DH https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange Diffie-Hellman key exchange is a method of securely exchanging cryptographic keys over a public channel and was one of the first public-key protocols as conceived by Ralph Merkle and named after Whitfield Diffie and Martin Hellman. DH is one of the earliest practical examples of public key exchange implemented within the field of cryptography. Published in 1976 by Diffie and Hellman, this is the earliest publicly known work that proposed the idea of a private key and a corresponding public key.

• Question 14:

  In 1977 researchers and MIT described what asymmetric algorithm?

  A. DH

  B. RSA

  C. AES

  D. EC

  Correct Answer: B

  RSA

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

  RSA (Rivest-Shamir-Adleman) 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.

• Question 15:

  Which of the following is the successor of SSL?

  A. GRE

  B. RSA

  C. IPSec

  D. TLS

  Correct Answer: D

  TLS

  https://en.wikipedia.org/wiki/Transport_Layer_Security#History_and_development TLS 1.0 was first defined in RFC 2246 in January 1999 as an upgrade of SSL Version 3.0, and written by Christopher Allen and Tim Dierks of Consensus

  Development. As stated in the RFC, "the differences between this protocol and SSL 3.0 are not dramatic, but they are significant enough to preclude interoperability between TLS 1.0 and SSL 3.0". Tim Dierks later wrote that these changes,

  and the renaming from "SSL" to "TLS", were a face-saving gesture to Microsoft, "so it wouldn't look [like] the IETF was just rubberstamping Netscape's protocol".

• Question 16:

  The most widely used asymmetric encryption algorithm is what?

  A. Vigenere

  B. Caesar Cipher

  C. RSA

  D. DES

  Correct Answer: C

  RSA The RSA encryption algorithm is one of the most widely used public key encryption algorithms that have ever been invented. It was created by the three scientists Ronald Rivest, Adi Shamir, and Leonard Adleman in 1977, and today it is increasingly being used in the network area.

• Question 17:

  What must occur in order for a cipher to be considered `broken'?

  A. Uncovering the algorithm used

  B. Decoding the key

  C. Finding any method that is more efficient than brute force

  D. Rendering the cipher no longer useable

  Correct Answer: C

  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."

• Question 18:

  A _________ is a digital representation of information that identifies you as a relevant entity by a trusted third party.

  A. Digital Signature

  B. Hash

  C. Ownership stamp

  D. Digest

  Correct Answer: A

  Digital Signature https://en.wikipedia.org/wiki/Digital_signature A digital signature is a mathematical scheme for verifying the authenticity of digital messages or documents. A valid digital signature, where the prerequisites are satisfied, gives a recipient very strong reason to believe that the message was created by a known sender (authentication), and that the message was not altered in transit (integrity).

• Question 19:

  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

  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 20:

  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

  Correct Answer: B

  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.