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EC-Council 212-81 Exam Questions
Certified Encryption Specialist (Page 7 )

Updated On: 24-Feb-2026
Page 7 of 43
PDF with 206 Questions

In a ______ the attacker discovers a functionally equivalent algorithm for encryption and decryption, but without learning the key.

  1. Information deduction
  2. Total break
  3. Instance deduction
  4. Global deduction

Answer(s): B

Explanation:

Global deduction https://en.wikipedia.org/wiki/Cryptanalysis
Global deduction -- the attacker discovers a functionally equivalent algorithm for encryption and decryption, but without learning the key.

Incorrect answers:
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.
Total break -- the attacker deduces the secret key.



Which of the following is a cryptographic protocol that allows two parties to establish a shared key over an insecure channel?

  1. Elliptic Curve
  2. NMD5
  3. RSA
  4. Diffie-Hellman

Answer(s): D

Explanation:

Diffie-Hellman 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 originally conceptualized 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.
Incorrect answers:
Elliptic Curve - Asymmetric Key Algorithm, provides encryption, digital signatures, key exchange, based on the idea of using points on a curve to define the public/private key, used in wireless devices and smart cards. The security of the Elliptic Curve cryptography is based on the fact that finding the discrete logarithm of a random elliptic curve element with respect to a publicly known base point is difficult to the point of being impractical to do so. (y2 = x3 + Ax + B) - Developed by Victor Miller and Neil Koblitz in 1985
MD5 - hash function - 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. Not collision resistant - Not Reversible - RFC 1321

RSA - is a public-key cryptosystem that is widely used for secure data transmission.



A linear congruential generator is an example of what?

  1. A coprime generator
  2. A prime number generator
  3. A pseudo random number generator
  4. A random number generator

Answer(s): C

Explanation:

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.



DES has a key space of what?

  1. 2^128
  2. 2^192
  3. 2^64
  4. 2^56

Answer(s): D

Explanation:

2^56

https://en.wikipedia.org/wiki/Data_Encryption_Standard
The Data Encryption Standard (DES) is a symmetric-key algorithm for the encryption of digital data. Although its short key length of 56 bits makes it too insecure for applications, it has been highly influential in the advancement of cryptography.



John works as a cryptography consultant. He finds that people often misunderstand the reality of breaking a cipher.
What is the definition of breaking a cipher?

  1. Finding any method that is more efficient than brute force
  2. Uncovering the algorithm used
  3. Rendering the cypher no longer useable
  4. Decoding the key

Answer(s): A

Explanation:

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. Never mind that brute-force might require 2^128 encryptions; an attack requiring 2^110 encryptions would be considered a break...simply put, a break can just be a certificational weakness: evidence that the cipher does not perform as advertised."






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