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Question 21

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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.

Whitening
Whitening
Key Exchange
Key Exchange
Key Schedule
Key Schedule
Key Clustering
Key Clustering
Suggested answer: A
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.

Incorrect answers:

Key Clustering - different encryption keys generated the same ciphertext from the same plaintext message.

Key Schedule - an algorithm for the key that calculates the subkeys for each round that the encryption goes through.

Key Exchange - a method in cryptography by which cryptographic keys are exchanged between two parties, allowing use of a cryptographic algorithm.

asked 18/09/2024
Alexey Chernikov
34 questions

Question 22

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A protocol for key aggreement based on Diffie-Hellman. Created in 1995. Incorporated into the public key standard IEEE P1363.

Blum Blum Shub
Blum Blum Shub
Elliptic Curve
Elliptic Curve
Menezes-Qu-Vanstone
Menezes-Qu-Vanstone
Euler's totient
Euler's totient
Suggested answer: C
Explanation:

Menezes-Qu-Vanstone

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

MQV (Menezes--Qu--Vanstone) is an authenticated protocol for key agreement based on the Diffie--Hellman scheme. Like other authenticated Diffie--Hellman 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).

MQV was initially proposed by Alfred Menezes, Minghua Qu and Scott Vanstone in 1995. It was modified with Law and Solinas in 1998.

Incorrect answers:

Elliptic Curve - an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields. ECC allows smaller keys compared to non-EC cryptography (based on plain Galois fields) to provide equivalent security.

Euler's totient - function counts the positive integers up to a given integer n that are relatively prime to n.

Blum Blum Shub - a pseudorandom number generator proposed in 1986 by Lenore Blum, Manuel Blum and Michael Shub that is derived from Michael O. Rabin's one-way function.

asked 18/09/2024
rene laas
56 questions

Question 23

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What is the largest key size that AES can use?

256
256
56
56
512
512
128
128
Suggested answer: A
Explanation:

256

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

For AES, NIST selected three members of the Rijndael family, each with a block size of 128 bits, but three different key lengths: 128, 192 and 256 bits.

asked 18/09/2024
Gerrit Struik
59 questions

Question 24

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Terrance oversees the key escrow server for his company. All employees use asymmetric cryptography to encrypt all emails. How many keys are needed for asymmetric cryptography?

2
2
4
4
3
3
1
1
Suggested answer: A
Explanation:

:

2

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.

asked 18/09/2024
Mahendra Belgaonkar
43 questions

Question 25

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Which of the following encryption algorithms relies on the inability to factor large prime numbers?

RSA
RSA
MQV
MQV
EC
EC
AES
AES
Suggested answer: A
Explanation:

Correct answers: RSA

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

RSA (Rivest--Shamir--Adleman) 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.

The security of RSA relies on the practical difficulty of factoring the product of two large prime numbers, the 'factoring problem'. Breaking RSA encryption is known as the RSA problem. Whether it is as difficult as the factoring problem is an open question. There are no published methods to defeat the system if a large enough key is used.

Incorrect answers:

EC - Elliptic-curve cryptography (ECC) is an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields. ECC allows smaller keys compared to non-EC cryptography (based on plain Galois fields) to provide equivalent security.

AES - Advanced Encryption Standard (AES), also known by its original name Rijndael, is a specification for the encryption of electronic data established by the U.S. National Institute of Standards and Technology (NIST) in 2001.

AES is a subset of the Rijndael block cipher developed by two Belgian cryptographers, Vincent Rijmen and Joan Daemen, who submitted a proposal to NIST during the AES selection process. Rijndael is a family of ciphers with different key and block sizes. For AES, NIST selected three members of the Rijndael family, each with a block size of 128 bits, but three different key lengths: 128, 192 and 256 bits.

MQV - (Menezes--Qu--Vanstone) is an authenticated protocol for key agreement based on the Diffie--Hellman scheme. Like other authenticated Diffie--Hellman 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).

asked 18/09/2024
Seth Frizzell
44 questions

Question 26

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If you XOR 10111000 with 10101010, what is the result?

10111010
10111010
10101010
10101010
11101101
11101101
00010010
00010010
Suggested answer: D
Explanation:

00010010

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

1 0 1 1 1 0 0 0

1 0 1 0 1 0 1 0

________________

0 0 0 1 0 0 1 0

asked 18/09/2024
J. Cuylits
37 questions

Question 27

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Which one of the following is a symmetric key system using 64-bit blocks?

DES
DES
PGP
PGP
DSA
DSA
RSA
RSA
Suggested answer: A
Explanation:

DES

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

DES is the archetypal block cipher---an algorithm that takes a fixed-length string of plaintext bits and transforms it through a series of complicated operations into another ciphertext bitstring of the same length. In the case of DES, the block size is 64 bits. DES also uses a key to customize the transformation, so that decryption can supposedly only be performed by those who know the particular key used to encrypt. The key ostensibly consists of 64 bits; however, only 56 of these are actually used by the algorithm. Eight bits are used solely for checking parity, and are thereafter discarded. Hence the effective key length is 56 bits.

Incorrect answers:

PGP - Pretty Good Privacy (PGP) is an encryption program that provides cryptographic privacy and authentication for data communication. PGP is used for signing, encrypting, and decrypting texts, e-mails, files, directories, and whole disk partitions and to increase the security of e-mail communications. Phil Zimmermann developed PGP in 1991.

RSA - RSA (Rivest--Shamir--Adleman) 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.

DSA - The Digital Signature Algorithm (DSA) is a Federal Information Processing Standard for digital signatures, based on the mathematical concept of modular exponentiation and the discrete logarithm problem. DSA is a variant of the Schnorr and ElGamal signature schemes.

asked 18/09/2024
Kathie Herod
42 questions

Question 28

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Ferris has been assigned the task of selecting security for his company's wireless network. It is important that he pick the strongest form of wireless security. Which one of the following is the strongest wireless security?

WEP
WEP
WPA
WPA
WPA2
WPA2
TKIP
TKIP
Suggested answer: C
Explanation:

WPA2

https://en.wikipedia.org/wiki/Wi-Fi_Protected_Access

WPA (sometimes referred to as the draft IEEE 802.11i standard) became available in 2003. The Wi-Fi Alliance intended it as an intermediate measure in anticipation of the availability of the more secure and complex WPA2, which became available in 2004 and is a common shorthand for the full IEEE 802.11i (or IEEE 802.11i-2004) standard.

asked 18/09/2024
Joe Evanchak
46 questions

Question 29

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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.

IV
IV
Salt
Salt
L2TP
L2TP
Nonce
Nonce
Suggested answer: A
Explanation:

IV

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.

Incorrect answers:

L2TP - PPTP combined with L2F (Layer 2 Forwarding) (Cisco proprietary protocol) - Uses EAP, CHAP, MS-CHAP, PAP, or S-PAP for authentication. IPSec is used to provide encryption.

Salt - random bits of data intermixed with the message that is to be hashed.

Nonce - an arbitrary number that can be used just once in a cryptographic communication. It is similar in spirit to a nonce word, hence the name. It is often a random or pseudo-random number issued in an authentication protocol to ensure that old communications cannot be reused in replay attacks. They can also be useful as initialization vectors and in cryptographic hash functions.

asked 18/09/2024
Carmina Medel
37 questions

Question 30

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A list of certificates that have been revoked.

CA
CA
CRL
CRL
PCBC
PCBC
OCSP
OCSP
Suggested answer: B
Explanation:

CRL

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

In cryptography, a 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'.

Incorrect answers:

PCBC - the propagating cipher block chaining or plaintext cipher-block chaining mode was designed to cause small changes in the ciphertext to propagate indefinitely when decrypting, as well as when encrypting. In PCBC mode, each block of plaintext is XORed with both the previous plaintext block and the previous ciphertext block before being encrypted. As with CBC mode, an initialization vector is used in the first block.

CA - certificate authority or certification authority is an entity that issues digital certificates.

OCSP - 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).

asked 18/09/2024
ANNA RIBALTA
37 questions
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