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

• Question 21:

  The most common way steganography is accomplished is via which one of the following?

  A. rsb

  B. Isb

  C. msb

  D. asb

  Correct Answer: B

  lbs

  https://en.wikipedia.org/wiki/Bit_numbering#:~:text=In%20computing%2C%20the%20least %20significant,number%20is%20even%20or%20odd.

  The least significant bit (LSB) is the bit position in a binary integer giving the units value, that is, determining whether the number is even or odd. The LSB is sometimes referred to as the low-order bit or right-most bit, due to the convention in

  positional notation of writing less significant digits further to the right. It is analogous to the least significant digit of a decimal integer, which is the digit in the ones (right-most) position.

• Question 22:

  A cryptanalysis success where the attacker discovers additional plain texts (or cipher texts) not previously known.

  A. Total Break

  B. Distinguishing Algorithm

  C. Instance Deduction

  D. Information Deduction

  Correct Answer: C

  Instance Deduction

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

  The results of cryptanalysis can also vary in usefulness. For example, cryptographer Lars Knudsen (1998) classified various types of attack on block ciphers according to the amount and quality of secret information that was discovered:

  Total break -- the attacker deduces the secret key. Global deduction -- the attacker discovers a functionally equivalent algorithm for encryption and decryption, but without learning the key. Instance (local) deduction -- the attacker discovers

  additional plaintexts (or ciphertexts) not previously known.

  Information deduction -- the attacker gains some Shannon information about plaintexts (or ciphertexts) not previously known.

  Distinguishing algorithm -- the attacker can distinguish the cipher from a random permutation.

• Question 23:

  Juanita is attempting to hide some text into a jpeg file. Hiding messages inside another medium is referred to as which one of the following?

  A. Cryptography

  B. Steganalysis

  C. Cryptology

  D. Steganography

  Correct Answer: D

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

• Question 24:

  The Clipper chip is notable in the history of cryptography for many reasons. First, it was designed for civilian used secure phones. Secondly, it was designed to use a very specific symmetric cipher. Which one of the following was originally designed to provide built-in cryptography for the Clipper chip?

  A. Blowfish

  B. Twofish

  C. Skipjack

  D. Serpent

  Correct Answer: C

  Skipjack https://en.wikipedia.org/wiki/Clipper_chip The Clipper chip was a chipset that was developed and promoted by the United States National Security Agency (NSA) as an encryption device that secured "voice and data messages" with a built-in backdoor that was intended to "allow Federal, State, and local law enforcement officials the ability to decode intercepted voice and data transmissions.". It was intended to be adopted by telecommunications companies for voice transmission. Introduced in 1993, it was entirely defunct by 1996. he Clipper chip used a data encryption algorithm called Skipjack to transmit information and the Diffie-Hellman key exchange-algorithm to distribute the cryptokeys between the peers. Skipjack was invented by the National Security Agency of the U.S. Government; this algorithm was initially classified SECRET, which prevented it from being subjected to peer review from the encryption research community. The government did state that it used an 80-bit key, that the algorithm was symmetric, and that it was similar to the DES algorithm. The Skipjack algorithm was declassified and published by the NSA on June 24, 1998. The initial cost of the chips was said to be $16 (unprogrammed) or $26 (programmed), with its logic designed by Mykotronx, and fabricated by VLSI Technology, Inc (see the VLSI logo on the image on this page).

• Question 25:

  Collision resistance is an important property for any hashing algorithm. Joan wants to find a cryptographic hash that has strong collision resistance. Which one of the following is the most collisionresistant?

  A. SHA2

  B. MD5

  C. MD4

  D. PIKE

  Correct Answer: A

  SHA2 https://en.wikipedia.org/wiki/Collision_resistance Collision resistance is a property of cryptographic hash functions: a hash function H is collision-resistant if it is hard to find two inputs that hash to the same output; that is, two inputs a and b where a b but H(a) = H(b). The pigeonhole principle means that any hash function with more inputs than outputs will necessarily have such collisions; the harder they are to find, the more cryptographically secure the hash function is. Due to the Birthday Problem, for a hash function that produces an output of length n bits, the probability of getting a collision is 1/2^n/2. So, just looking for a hash function with larger "n". The SHA-2 family consists of six hash functions with digests (hash values) that are 224, 256, 384 or 512 bits: SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224, SHA- 512/256.

• Question 26:

  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

  Correct Answer: C

  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 27:

  Nicholas is working at a bank in Germany. He is looking at German standards for pseudo random number generators. He wants a good PRNG for generating symmetric keys. The German Federal Office for Information Security (BSI) has established four criteria for quality of random number generators. Which ones can be used for cryptography?

  A. K4

  B. K5

  C. K3

  D. K2

  E. K1

  Correct Answer: AC

• Question 28:

  Which of the following areas is considered a strength of symmetric key cryptography when compared with asymmetric algorithms?

  A. Key distribution

  B. Security

  C. Scalability

  D. Speed

  Correct Answer: D

  Speed

  Symmetric key systems are considerably faster than asymmetric key systems but have issues with proper key distribution, controlling keys as more users need to communicate, and cannot provide non-repudiation or authenticity.

• Question 29:

  During the process of encryption and decryption, what keys are shared?

  A. Public keys

  B. Public and private keys

  C. User passwords

  D. Private keys

  Correct Answer: A

  Public keys https://en.wikipedia.org/wiki/Public-key_cryptography Public-key cryptography, or 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. In such a system, any person can encrypt a message using the receiver's public key, but that encrypted message can only be decrypted with the receiver's private key.

  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.

  Alice and Bob do not need to plan anything ahead of time to communicate securely: they generate their public-private key pairs independently, and happily broadcast their public keys to the world at large. Alice can rest assured that only Bob can decrypt the message she sends because she has encrypted it with his public key.

• Question 30:

  Cylinder tool. Wrap leather around to decode. The diameter is the key. Used in 7th century BC by greek poet Archilochus.

  A. Cipher disk

  B. Caesar cipher

  C. Scytale

  D. Enigma machine

  Correct Answer: C

  Scytale https://en.wikipedia.org/wiki/Scytale A scytale is a tool used to perform a transposition cipher, consisting of a cylinder with a strip of parchment wound around it on which is written a message. The ancient Greeks, and the Spartans in particular, are said to have used this cipher in 7th century BC to communicate during military campaigns. The recipient uses a rod of the same diameter on which the parchment is wrapped to read the message. It has the advantage of being fast and not prone to mistakes--a necessary property when on the battlefield. It can, however, be easily broken. Since the strip of parchment hints strongly at the method, the ciphertext would have to be transferred to something less suggestive, somewhat reducing the advantage noted.