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

EC-COUNCIL 212-81 Online Questions & Answers

• Question 1:

  A technique used to increase the security of block ciphers. It consists of steps that combine the data with portions of the key (most commonly using a simple XOR) before the first round and after the last round of encryption.

  A. Whitening
  B. Key Exchange
  C. Key Schedule
  D. Key Clustering
  A. Whitening

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  Explanation

  Whitening https://en.wikipedia.org/wiki/Key_whitening In cryptography, key whitening is a technique intended to increase the security of an iterated block cipher. It consists of steps that combine the data with portions of the key. The most common form of key whitening is xor-encrypt-xor -- using a simple XOR before the first round and after the last round of encryption. The first block cipher to use a form of key whitening is DES-X, which simply uses two extra 64-bit keys for whitening, beyond the normal 56-bit key of DES. This is intended to increase the complexity of a brute force attack, increasing the effective size of the key without major changes in the algorithm. DES-X's inventor, Ron Rivest, named the technique whitening.

• Question 2:

  What is the basis for the difficulty in breaking RSA?

  A. Hashing
  B. The birthday paradox
  C. Equations that describe an elliptic curve
  D. Factoring numbers
  D. Factoring numbers

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  Explanation

  Factoring numbers

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

  RSA (Rivest璖hamir瑼dleman) 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. In a public-key cryptosystem, the encryption key is public and distinct from the decryption key, which is kept secret (private). An RSA user creates and publishes a public key based on two large prime numbers, along with an auxiliary value.

  The prime numbers are kept secret. Messages can be encrypted by anyone, via the public key, but can only be decoded by someone who knows the prime numbers.

• Question 3:

  Which of the following is a key exchange protocol?

  A. MQV
  B. AES
  C. DES
  D. RSA
  A. MQV

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  Explanation

  MQV https://en.wikipedia.org/wiki/MQV MQV (Menezes璔u璙anstone) is an authenticated protocol for key agreement based on the Diffie璈ellman scheme. Like other authenticated Diffie璈ellman 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 4:

  A cryptographic hash function which uses a Merkle tree-like structure to allow for immense parallel computation of hashes for very long inputs. Authors claim a performance of 28 cycles per byte for MD6-256 on an Intel Core 2 Duo and provable resistance against differential cryptanalysis.

  A. TIGER
  B. GOST
  C. MD5
  D. MD6
  D. MD6

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  Explanation

  MD6 https://en.wikipedia.org/wiki/MD6 The MD6 Message-Digest Algorithm is a cryptographic hash function. It uses a Merkle tree- like structure to allow for immense parallel computation of hashes for very long inputs. Authors claim a performance of 28 cycles per byte for MD6256 on an Intel Core 2 Duo and provable resistance against differential cryptanalysis.[2] The source code of the reference implementation was released under MIT license. Speeds in excess of 1 GB/s have been reported to be possible for long messages on 16- core CPU architecture. In December 2008, Douglas Held of Fortify Software discovered a buffer overflow in the original MD6 hash algorithm's reference implementation. This error was later made public by Ron Rivest on 19 February 2009, with a release of a corrected reference implementation in advance of the Fortify Report.

• Question 5:

  A non-secret binary vector used as the initializing input algorithm for encryption of a plaintext block sequence to increase security by introducing additional cryptographic variance.

  A. IV
  B. Salt
  C. L2TP
  D. Nonce
  A. IV

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  Explanation

  https://en.wikipedia.org/wiki/Initialization_vector In cryptography, an initialization vector (IV) or starting variable (SV) is a fixed-size input to a cryptographic primitive that is typically required to be random or pseudorandom. Randomization is crucial for encryption schemes to achieve semantic security, a property whereby repeated usage of the scheme under the same key does not allow an attacker to infer relationships between segments of the encrypted message. For block ciphers, the use of an IV is described by the modes of operation. Randomization is also required for other primitives, such as universal hash functions and message authentication codes based thereon.

• Question 6:

  What does the OCSP protocol provide?

  A. Revoked certificates
  B. Hashing
  C. VPN connectivity
  D. Encryption
  A. Revoked certificates

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  Explanation

  Revoked certificates https://en.wikipedia.org/wiki/Online_Certificate_Status_Protocol The Online Certificate Status Protocol (OCSP) is an Internet protocol used for obtaining the revocation status of an X.509 digital certificate.It is described in RFC 6960 and is on the Internet standards track. It was created as an alternative to certificate revocation lists (CRL), specifically addressing certain problems associated with using CRLs in a public key infrastructure (PKI). Messages communicated via OCSP are encoded in ASN.1 and are usually communicated over HTTP. The "request/response" nature of these messages leads to OCSP servers being termed OCSP responders.

• Question 7:

  A real time protocol for verifying certificates (and a newer method than CRL).

  A. Online Certificate Status Protocol (OCSP)
  B. Server-based Certificate Validation Protocol (SCVP)
  C. Public Key Infrastructure (PKI)
  D. Registration Authority (RA)
  A. Online Certificate Status Protocol (OCSP)

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  Explanation

  Online Certificate Status Protocol (OCSP)

  https://en.wikipedia.org/wiki/Online_Certificate_Status_Protocol The Online Certificate Status Protocol (OCSP) is an Internet protocol used for obtaining the revocation status of an X.509 digital certificate. It is described in RFC 6960 and is on

  the Internet standards track. It was created as an alternative to certificate revocation lists (CRL), specifically addressing certain problems associated with using CRLs in a public key infrastructure (PKI).

• Question 8:

  Created by

  D.

  H. Lehmer. It is a classic example of a Linear congruential generator. A PRNG type of linear congruential generator (LCG) that operates in multiplicative group of integers modulo n. The basic algorithm is Xi+1=(aXi + c) mod m, with 0 Xi m.

  A. Lehmer Random Number Generator
  B. Lagged Fibonacci Generator
  C. Linear Congruential Generator
  D. Blum Blum Shub
  A. Lehmer Random Number Generator

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  Explanation

  Lehmer Random Number Generator https://en.wikipedia.org/wiki/Lehmer_random_number_generator The Lehmer random number generator (named after

  D.

  H. Lehmer), sometimes also referred to as the Park璏iller random number generator (after Stephen K. Park and Keith

  W. Miller), is a type of linear congruential generator (LCG) that operates in multiplicative group of integers modulo n. The general formula is:

  where the modulus m is a prime number or a power of a prime number, the multiplier a is an element of high multiplicative order modulo m (e.g., a primitive root modulo n), and the seed X0 is coprime to m. Other names are multiplicative linear congruential generator (MLCG) and multiplicative congruential generator (MCG).

• Question 9:

  A digital document that contains a public key and some information to allow your system to verify where that key came from. Used for web servers, Cisco Secure phones, E- Commerce.

  A. Registration Authority
  B. Payload
  C. OCSP
  D. Digital Certificate
  D. Digital Certificate

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  Explanation

  Digital Certificate https://en.wikipedia.org/wiki/Public_key_certificate A public key certificate, also known as a digital certificate or identity certificate, is an electronic document used to prove the ownership of a public key. The certificate includes information about the key, information about the identity of its owner (called the subject), and the digital signature of an entity that has verified the certificate's contents (called the issuer).

• Question 10:

  Which of the following Secure Hashing Algorithm (SHA) produces a 160-bit digest from a message with a maximum length of (264-1) bits and resembles the MD5 algorithm?

  A. SHA-0
  B. SHA-2
  C. SHA-1
  D. SHA-3
  C. SHA-1

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  Explanation

  SHA-1 https://en.wikipedia.org/wiki/SHA-1 SHA-1 (Secure Hash Algorithm 1) is a cryptographic hash function which takes an input and produces a 160-bit (20-byte) hash value known as a message digest ?typically rendered as a hexadecimal number, 40 digits long. It was designed by the United States National Security Agency, and is a U.S. Federal Information Processing Standard. SHA-1 produces a message digest based on principles similar to those used by Ronald L. Rivest of MIT in the design of the MD2, MD4 and MD5 message digest algorithms, but generates a larger hash value (160 bits vs. 128 bits).