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Free 212-81 Exam Braindumps (page: 18)

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PDF with 206 Questions

The concept that if one bit of data changes, the cipher text will all completely change as well.

  1. Avalanche
  2. Substitution
  3. Confusion
  4. Collision

Answer(s): A

Explanation:

Avalanche https://en.wikipedia.org/wiki/Avalanche_effect
In cryptography, the avalanche effect is the desirable property of cryptographic algorithms, typically block ciphers and cryptographic hash functions, wherein if an input is changed slightly (for example, flipping a single bit), the output changes significantly (e.g., half the output bits flip). In the case of high-quality block ciphers, such a small change in either the key or the plaintext should cause a drastic change in the ciphertext. The actual term was first used by Horst Feistel, although the concept dates back to at least Shannon's diffusion.
Incorrect answers:
Confusion - Confusion means that each binary digit (bit) of the ciphertext should depend on several parts of the key, obscuring the connections between the two.
The property of confusion hides the relationship between the ciphertext and the key.
This property makes it difficult to find the key from the ciphertext and if a single bit in a key is changed, the calculation of the values of most or all of the bits in the ciphertext will be affected. Confusion increases the ambiguity of ciphertext and it is used by both block and stream ciphers. Substitution - method of encrypting by which units of plaintext are replaced with ciphertext, according to a fixed system; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by performing the inverse substitution.
Collision - occurs when a hash function generates the same output for different inputs.



Bruce Schneier is a well-known and highly respected cryptographer. He has developed several pseudo random number generators as well as worked on teams developing symmetric ciphers. Which one of the following is a symmetric block cipher designed in 1993 by Bruce Schneier team that is unpatented?

  1. Pegasus
  2. Blowfish
  3. SHA1
  4. AES

Answer(s): A

Explanation:

Blowfish https://en.wikipedia.org/wiki/Blowfish_(cipher)
Blowfish is a symmetric-key block cipher, designed in 1993 by Bruce Schneier and included in many cipher suites and encryption products.



Software for maintaining an on-the-fly-encrypted volume. Data is automatically encrypted right before it is saved, then decrypted right after it is loaded, all w/o user intervention.

  1. VPN
  2. PGP
  3. Cryptool
  4. VeraCrypt

Answer(s): D

Explanation:

VeraCrypt https://en.wikipedia.org/wiki/VeraCrypt
VeraCrypt is a source-available freeware utility used for on-the-fly encryption (OTFE). It can create a virtual encrypted disk within a file or encrypt a partition or (in Windows) the entire storage device
with pre-boot authentication.

Incorrect answers:
PGP - designed by Phil Zimmerman as a freeware e-mail security program and was released in 1991. It was the first widespread public key encryption program.
VPN - A virtual private network (VPN) extends a private network across a public network and enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network. Applications running across a VPN may therefore benefit from the functionality, security, and management of the private network. Encryption is a common, although not an inherent, part of a VPN connection
Cryptool - an open-source project that focuses on the free e-learning software CrypTool illustrating cryptographic and cryptanalytic concepts. According to "Hakin9", CrypTool is worldwide the most widespread e-learning software in the field of cryptology.



Which of the following statements is most true regarding binary operations and encryption?

  1. They can provide secure encryption
  2. They are only useful as a teaching method
  3. They can form a part of viable encryption methods
  4. They are completely useless

Answer(s): C

Explanation:

They can form a part of viable encryption methods for example - https://en.wikipedia.org/wiki/XOR_cipher
The XOR operator is extremely common as a component in more complex ciphers. By itself, using a constant repeating key, a simple XOR cipher can trivially be broken using frequency analysis. If the content of any message can be guessed or otherwise known then the key can be revealed. Its primary merit is that it is simple to implement, and that the XOR operation is computationally inexpensive. A simple repeating XOR (i.e. using the same key for xor operation on the whole data) cipher is therefore sometimes used for hiding information in cases where no particular security is required. The XOR cipher is often used in computer malware to make reverse engineering more difficult.






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