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

• Question 141:

  What does Output feedback (OFB) do:

  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. A block cipher is converted into a stream cipher by generating a keystream blocks, which are then XORed with the plaintext blocks to get the ciphertext

  D. The cipher text from the current round is XORed with the plaintext for the next round

  Correct Answer: C

  A block cipher is converted into a stream cipher by generating a keystream blocks, which are then XORed with the plaintext blocks to get the ciphertext 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 142:

  The greatest weakness with symmetric algorithms is _____.

  A. They are less secure than asymmetric

  B. The problem of key exchange

  C. The problem of generating keys

  D. They are slower than asymmetric

  Correct Answer: B

  The problem of key exchange https://en.wikipedia.org/wiki/Symmetric-key_algorithm Symmetric-key algorithms are algorithms for cryptography that use the same cryptographic keys for both encryption of plaintext and decryption of ciphertext. The keys may be identical or there may be a simple transformation to go between the two keys. The keys, in practice, represent a shared secret between two or more parties that can be used to maintain a private information link. This requirement that both parties have access to the secret key is one of the main drawbacks of symmetric key encryption, in comparison to public-key encryption (also known as asymmetric key encryption).

• Question 143:

  Asymmetric encryption method developed in 1984. It is used in PGP implementations and GNU Privacy Guard Software. Consists of 3 parts: key generator, encryption algorithm, and decryption algorithm.

  A. Tiger

  B. GOST

  C. RIPEMD

  D. ElGamal

  Correct Answer: D

  ElGamal https://en.wikipedia.org/wiki/ElGamal_encryption the ElGamal encryption system is an asymmetric key encryption algorithm for public-key cryptography which is based on the Diffie-Hellman key exchange. It was described by Taher Elgamal in 1985. ElGamal encryption is used in the free GNU Privacy Guard software, recent versions of PGP, and other cryptosystems. The Digital Signature Algorithm (DSA) is a variant of the ElGamal signature scheme, which should not be confused with ElGamal encryption.

• Question 144:

  As a network administrator, you have implemented WPA2 encryption in your corporate wireless network. The WPA2's ________ integrity check mechanism provides security against a replay attack.

  A. CBC-MAC

  B. CRC-MAC

  C. CRC-32

  D. CBC-32

  Correct Answer: A

  CBC-MAC https://en.wikipedia.org/wiki/CBC-MAC A cipher block chaining message authentication code (CBC-MAC) is a technique for constructing a message authentication code from a block cipher. The message is encrypted with some block cipher algorithm in CBC mode to create a chain of blocks such that each block depends on the proper encryption of the previous block. This interdependence ensures that a change to any of the plaintext bits will cause the final encrypted block to change in a way that cannot be predicted or counteracted without knowing the key to the block cipher. Using in WPA2 for integrity check and provides security against a replay attack.

• Question 145:

  This algorithm was published by the German engineering firm Seimans in 1993. It is a software based stream cipher using Lagged Fibonacci generator along with a concept borrowed from the shrinking generator ciphers.

  A. RC4

  B. Blowfish

  C. Twofish

  D. FISH

  Correct Answer: D

  FISH

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

  The FISH (FIbonacci SHrinking) stream cipher is a fast software based stream cipher using Lagged Fibonacci generators, plus a concept from the shrinking generator cipher. It was published by Siemens in 1993. FISH is quite fast in software

  and has a huge key length. However, in the same paper where he proposed Pike, Ross Anderson showed that FISH can be broken with just a few thousand bits of known plaintext.

• Question 146:

  Bruce Schneier is a well-known and highly respected cryptographer. He has developed several pseudo random number generators as well as worked on teams developing symmetric ciphers. Which one of the following is a symmetric block cipher designed in 1993 by Bruce Schneier team that is unpatented?

  A. Pegasus

  B. Blowfish

  C. SHA1

  D. AES

  Correct Answer: A

  Blowfish

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

  Blowfish is a symmetric-key block cipher, designed in 1993 by Bruce Schneier and included in many cipher suites and encryption products.

• Question 147:

  Which of the following techniques is used (other than brute force) to attempt to derive a key?

  A. Cryptography

  B. Cryptoanalysis

  C. Password cracking

  D. Hacking

  Correct Answer: B

  Cryptoanalysis https://en.wikipedia.org/wiki/Cryptanalysis Cryptanalysis is the study of analyzing information systems in order to study the hidden aspects of the systems. Cryptanalysis is used to breach cryptographic security systems and gain access to the contents of encrypted messages, even if the cryptographic key is unknown.

• Question 148:

  Developed by Netscape and has been replaced by TLS. It was the preferred method used with secure websites.

  A. OCSP

  B. VPN

  C. CRL

  D. SSL

  Correct Answer: D

  SSL https://en.wikipedia.org/wiki/Transport_Layer_Security Transport Layer Security (TLS), and its now-deprecated predecessor, Secure Sockets Layer (SSL), are cryptographic protocols designed to provide communications security over a computer network. Several versions of the protocols find widespread use in applications such as web browsing, email, instant messaging, and voice over IP (VoIP). Websites can use TLS to secure all communications between their servers and web browsers. Netscape developed the original SSL protocols, and Taher Elgamal, chief scientist at Netscape Communications from 1995 to 1998, has been described as the "father of SSL". SSL version 1.0 was never publicly released because of serious security flaws in the protocol. Version 2.0, released in February 1995, contained a number of security flaws which necessitated the design of version 3.0. Released in 1996, SSL version 3.0 represented a complete redesign of the protocol produced by Paul Kocher working with Netscape engineers Phil Karlton and Alan Freier, with a reference implementation by Christopher Allen and Tim Dierks of Consensus Development.

• Question 149:

  Which of the following is a key exchange protocol?

  A. MQV

  B. AES

  C. DES

  D. RSA

  Correct Answer: A

  MQV https://en.wikipedia.org/wiki/MQV MQV (Menezes-Qu-Vanstone) is an authenticated protocol for key agreement based on the Diffie-Hellman scheme. Like other authenticated Diffie-Hellman schemes, MQV provides protection against an active attacker. The protocol can be modified to work in an arbitrary finite group, and, in particular, elliptic curve groups, where it is known as elliptic curve MQV (ECMQV).

• Question 150:

  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

  Correct Answer: C

  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.