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

• Question 191:

  If you XOR 10111000 with 10101010, what is the result?

  A. 10111010

  B. 10101010

  C. 11101101

  D. 00010010

  Correct Answer: D

  https://en.wikipedia.org/wiki/XOR_cipher 1 0 1 1 1 0 0 0 1 0 1 0 1 0 1 0

  0 0 0 1 0 0 1 0

• Question 192:

  Ciphers that write message letters out diagonally over a number of rows then read off cipher row by row. Also called zig-zag cipher.

  A. Rail Fence Cipher

  B. Null Cipher

  C. Vigenere Cipher

  D. ROT-13

  Correct Answer: A

  Rail Fence Cipher https://en.wikipedia.org/wiki/Rail_fence_cipher The rail fence cipher (also called a zigzag cipher) is a form of transposition cipher. It derives its name from the way in which it is encoded.

• Question 193:

  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

  Correct Answer: C

  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. 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 194:

  A symmetric Stream Cipher published by the German engineering firm Seimans in 1993. A software based stream cipher that uses a Lagged Fibonacci generator along with concepts borrowed from shrinking generator ciphers.

  A. DESX

  B. FISH

  C. Twofish

  D. IDEA

  Correct Answer: B

  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 195:

  What type of encryption uses different keys to encrypt and decrypt the message?

  A. Asymmetric

  B. Symmetric

  C. Secure

  D. Private key

  Correct Answer: A

  Asymmetric https://en.wikipedia.org/wiki/Public-key_cryptography Asymmetric cryptography, is a cryptographic system that uses pairs of keys: public keys, which may be disseminated widely, and private keys, which are known only to the owner. The generation of such keys depends on cryptographic algorithms based on mathematical problems to produce one-way functions. Effective security only requires keeping the private key private; the public key can be openly distributed without compromising security.

• Question 196:

  A linear congruential generator is an example of what?

  A. A coprime generator

  B. A prime number generator

  C. A pseudo random number generator

  D. A random number generator

  Correct Answer: C

  A pseudo random number generator https://en.wikipedia.org/wiki/Linear_congruential_generator A linear congruential generator (LCG) is an algorithm that yields a sequence of pseudo- randomized numbers calculated with a discontinuous piecewise linear equation. The method represents one of the oldest and best-known pseudorandom number generator algorithms. The theory behind them is relatively easy to understand, and they are easily implemented and fast, especially on computer hardware which can provide modular arithmetic by storage-bit truncation.

• Question 197:

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

  A. 3DES

  B. AES

  C. RSA

  D. DES

  Correct Answer: A

  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 198:

  A 160-bit hash algorithm developed by Hans Dobbertin, Antoon Bosselaers, and Bart Preneel for which there are 128, 256 and 320-bit versions is called what?

  A. SHA1

  B. MD5

  C. FORK

  D. RIPEMD

  Correct Answer: D

  RIPEMD https://en.wikipedia.org/wiki/RIPEMD RIPEMD (RIPE Message Digest) is a family of cryptographic hash functions developed in 1992 (the original RIPEMD) and 1996 (other variants). There are five functions in the family: RIPEMD, RIPEMD-128, RIPEMD-160, RIPEMD-256, and RIPEMD-320, of which RIPEMD-160 is the most common. The original RIPEMD, as well as RIPEMD-128, is not considered secure because 128-bit result is too small and also (for the original RIPEMD) because of design weaknesses. The 256- and 320-bit versions of RIPEMD provide the same level of security as RIPEMD-128 and RIPEMD-160, respectively; they are designed for applications where the security level is sufficient but longer hash result is necessary.

• Question 199:

  Basic information theory is the basis for modern symmetric ciphers. Understanding the terminology of information theory is, therefore, important. Changes to one character in the plaintext affect multiple characters in the ciphertext. What is this referred to?

  A. Avalanche

  B. Confusion

  C. Scrambling

  D. Diffusion

  Correct Answer: D

  Diffusion https://en.wikipedia.org/wiki/Confusion_and_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. 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. The idea of diffusion is to hide the relationship between the ciphertext and the plain text. This will make it hard for an attacker who tries to find out the plain text and it increases the redundancy of plain text by spreading it across the rows and columns; it is achieved through transposition of algorithm and it is used by block ciphers only