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Free 212-81 Exam Braindumps (page: 13)

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PDF with 206 Questions

Which of the following is a fundamental principle of cryptography that holds that the algorithm can be publicly disclosed without damaging security?

  1. Vigenere's principle
  2. Shamir's principle
  3. Kerkchoff's principle
  4. Babbage's principle

Answer(s): C

Explanation:

Kerkchoff's principle
https://en.wikipedia.org/wiki/Kerckhoffs%27s_principle
Kerckhoffs's principle (also called Kerckhoffs's desideratum, assumption, axiom, doctrine or law) of cryptography was stated by Netherlands born cryptographer Auguste Kerckhoffs in the 19th century: A cryptosystem should be secure even if everything about the system, except the key, is public knowledge.
Kerckhoffs's principle was reformulated (or possibly independently formulated) by American mathematician Claude Shannon as "the enemy knows the system", i.e., "one ought to design systems under the assumption that the enemy will immediately gain full familiarity with them". In that form, it is called Shannon's maxim. This concept is widely embraced by cryptographers, in contrast to "security through obscurity", which is not.



A method for cracking modern cryptography. The attacker obtains the cipher texts corresponding to a set of plain texts of own choosing. Allows the attacker to attempt to derive the key. Difficult but not impossible.

  1. Chosen Plaintext Attack
  2. Steganography
  3. Rainbow Tables
  4. Transposition

Answer(s): A

Explanation:

Chosen Plaintext Attack https://en.wikipedia.org/wiki/Chosen-plaintext_attack
A chosen-plaintext attack (CPA) is an attack model for cryptanalysis which presumes that the attacker can obtain the ciphertexts for arbitrary plaintexts. The goal of the attack is to gain information that reduces the security of the encryption scheme.

Incorrect answers:
Rainbow Tables - precomputed table for caching the output of cryptographic hash functions, usually for cracking password hashes.
Transposition - swapping blocks of text.
Steganography - the practice of concealing a file, message, image, or video within another file, message, image, or video.



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.

  1. Registration Authority
  2. Payload
  3. OCSP
  4. Digital Certificate

Answer(s): D

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).

Incorrect answers:
OCSP - Provides certificate validation in real time and will let you know if it is valid or has been revoked.
Registration Authority (RA) - component of PKI that validates the identity of an entity requesting a digital certificate.
Payload - In computing and telecommunications, the payload is the part of transmitted data that is the actual intended message. Headers and metadata are sent only to enable payload delivery. In the steganography - information to be concealed and sent secretly, or the data covertly communicated;



Which one of the following are characteristics of a hash function? (Choose two)

  1. Requires a key
  2. One-way
  3. Fixed length output
  4. Symmetric
  5. Fast

Answer(s): B,C

Explanation:

Correct answers: One-way, Fixed length output https://en.wikipedia.org/wiki/Cryptographic_hash_function
A cryptographic hash function is a mathematical algorithm that maps data of arbitrary size (often called the "message") to a bit array of a fixed size (the "hash value", "hash", or "message digest"). It is a one-way function, that is, a function which is practically infeasible to invert. Incorrect answers:
Symmetric. Cryptographic algorithms can be categorized into three classes: Hash functions, Symmetric and Asymmetric algorithms. Differences: purpose and main fields of application.
Requires a key. Well, technically, this is the correct answer. But in the hash-function, “key” is input data.
Fast. Fast or slow is a subjective characteristic, there are many different algorithms, and here it is impossible to say this unambiguously like "Symmetric encryption is generally faster than asymmetric encryption."






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