In cryptography, what is the main purpose of encryption?

To obscure the meaning of data for unauthorized users

To compress data for faster transmission

To increase the file size before sending

To create an exact duplicate of the data

Which of the following is a key concept of Kirchhoff's principle in cryptography?

The security of a cipher must not depend on its key

A cipher should rely on secret algorithms

The same key is used by both sender and receiver

The algorithm must be changed frequently

A stream cipher typically encrypts data

Only when the file is fully received

Using a complex steganographic scheme

Which of the following is an example of a transposition cipher characteristic?

Rearranging the order of letters in the plaintext

Changing each letter of the plaintext to another letter

Concealing data within an image file

Using multiple alphabets to encrypt

Which of the following describes a monoalphabetic substitution cipher?

It replaces each plaintext character with a single ciphertext character consistently

It shifts letters by varying positions based on key length

It uses multiple substitution alphabets

It is primarily a form of transposition

In the context of security principles, 'Authentication' ensures

The user or system is who they claim to be

Data is only accessible to authorized users

The intended recipient cannot deny receiving data

Data remains consistent and unaltered

Which one of the following best illustrates a passive attack?

Using a keylogger to secretly record passwords

Modifying a financial transaction amount

Deleting a user's files from the server

Sending unsolicited traffic to crash a system

Which of the following statements is true about a worm?

It can spread independently across networks

It spreads only when a user executes it manually

The goal of cryptanalysis is to

Break or weaken existing encryption schemes

Secure communication channels through strong encryption

Design new forms of cipher algorithms

Hide data within other data structures

Which of the following is crucial for stream cipher operation?

A continuously changing key stream

A complex transposition function

Storing large amounts of encrypted data at once

"Keyless transposition cipher" means

The positions of characters are shuffled in a predefined pattern

The cipher is extremely secure due to random keys

The key is stored externally from the algorithm

A single key is reused for all encryption processes

How does the principle of 'Least Privilege' relate to the need for security in an organization?

It ensures users have the minimum level of access needed to perform their tasks

It restricts all users to only administrator rights

It gives each user unlimited access to ensure efficiency

It removes password protections for internal users

Why is non-repudiation particularly important in e-commerce transactions?

It provides evidence of the origin and authenticity of the transaction

It allows the seller to repudiate all transactions if there is a dispute

It ensures that no data can be read by unauthorized parties

It encrypts all webpages automatically

When comparing a virus and a Trojan horse, which key difference is most accurate?

Viruses self-replicate via infected files, while Trojan horses conceal malicious code within legitimate software

Viruses do not replicate, while Trojan horses replicate themselves

Trojan horses rely on a host program, while viruses operate independently

Both viruses and Trojan horses spread without user interaction

Which of the following statements about steganography is correct?

It focuses on hiding the existence of a message rather than just its content

It replaces encryption entirely

It is typically easier to detect than cryptography

It prevents any unauthorized interception of data

How does Kirchhoff's principle enhance the reliability of a cryptosystem?

By allowing the cryptosystem to remain secure even if the algorithm is public

By ensuring the secrecy of the encryption algorithm

By making certain that only symmetric keys are used

By mandating the use of transposition ciphers over substitution ciphers

In a monoalphabetic substitution cipher, what is the primary weakness that cryptanalysts exploit?

Frequency analysis of letters reveals patterns

The transposition pattern is easily guessed

The cipher cannot handle numeric data

Which statement accurately contrasts block ciphers with stream ciphers?

Block ciphers encrypt fixed-size chunks of data, while stream ciphers encrypt data bit by bit

Block ciphers typically encrypt data one bit at a time, stream ciphers encrypt entire blocks at once

Stream ciphers are more suitable for large data blocks, while block ciphers are used for continuous streams

Both are identical, except block ciphers require a longer key

A keyed transposition cipher differs from a keyless transposition cipher primarily in

The use of a secret key to determine the rearrangement pattern

Its reliance on frequency analysis for decryption

Its ability to hide data within media files

It can only be used for small messages

When performing cryptanalysis on a polyalphabetic cipher such as the Vigenère Cipher, one common technique is

The Kasiski examination or the Friedman test

Counting the number of repeated characters

Reordering the plaintext columns

Why is a Trojan horse potentially more dangerous than a simple virus?

A Trojan horse can provide backdoor access to a hacker

A Trojan horse can autonomously spread between hosts

A Trojan horse immediately deletes system files upon activation

A Trojan horse always encrypts user data for ransom

Why might a passive attack be more difficult to detect than an active attack?

They do not alter the data or system, leaving fewer traces

Passive attacks typically involve denial-of-service

They always involve high traffic volumes

Hackers announce their presence after a passive attack

What is the primary benefit of using a substitution cipher?

It ensures a one-to-one mapping of plaintext to ciphertext characters

It rearranges characters to conceal the real message

It is immune to all known cryptanalysis methods

It adds random data to the message for integrity

A brute-force cryptanalysis attempt on a symmetric key cipher would involve

Trying every possible key until the correct one is discovered

Using complex mathematics to find relationships in ciphertext

Hiding encrypted data inside an image file

Analyzing frequency distribution of letter usage

In symmetric key encipherment, which of the following must be done to ensure secure communication?

Both parties must share the same secret key securely beforehand

The public key of the receiver must be shared with the sender

No keys are required since the algorithm remains secret

Each message is encrypted with a different algorithm

Which best describes the 'availability' aspect of information security?

Ensuring that information can be accessed when needed

Restricting access only to authorized users

Guaranteeing that no one can modify data

Preventing attackers from reading data

Which scenario illustrates the concept of non-repudiation in digital communications?

Employing digital signatures so that senders cannot deny sending messages

Using a firewall to block unauthorized traffic

Implementing strong passwords to authenticate users

Encrypting all files on a hard drive

In a keyed transposition cipher, what could be a potential disadvantage compared to a keyless one?

Storing and sharing the key securely adds complexity

The rearrangement pattern is too random to be secure

Keyed ciphers are always less secure than keyless ones

The plaintext cannot contain numbers or special characters

How does a worm typically differ from a Trojan horse in terms of propagation?

Worms replicate automatically, whereas Trojan horses are installed via deception

Worms require user interaction to spread, Trojan horses do not

Both worms and Trojan horses replicate only when attached to emails

Trojan horses are always malicious, while worms can be harmless

Which factor most significantly impacts the strength of a polyalphabetic cipher?

The length and complexity of the key

The format of the plaintext file

The choice of hashing algorithm

Explain how frequency analysis can be adapted for a polyalphabetic cipher and the typical steps cryptanalysts take to overcome the added complexity.

By dividing the ciphertext into segments based on suspected key length and applying frequency analysis separately

By applying a simple letter frequency table to the entire ciphertext

By inserting dummy characters into the plaintext to mask frequency patterns

By encoding the ciphertext again with a different cipher

When designing a symmetric key cipher, why must developers consider both confusion and diffusion properties?

To ensure the ciphertext has no structural relation with the plaintext

To guarantee keys never repeat during encryption

So that the encryption can be reversed only by the intended recipient

Because confusion focuses on rearranging bits, while diffusion focuses on substituting characters

Kirchhoff's principle suggests that a cryptosystem should remain secure even if the adversary knows everything about the system except the key. In modern practice, how does this influence the design and evaluation of encryption algorithms?

It fosters open-source development and peer review of cryptographic algorithms

It encourages reliance on obscurity of algorithms to increase security

It mandates that hardware must remain proprietary and undisclosed

It allows weaker ciphers to remain in use if the key length is sufficient

In what scenario might a transposition cipher provide a security advantage over a simple substitution cipher, despite both being classical ciphers?

When the attacker relies solely on letter frequency analysis

When the plaintext includes many non-alphabetic symbols

If the transposition pattern is repeated multiple times

If no key is required for the transposition

In a block cipher operating in a mode that propagates changes in one block to subsequent blocks (e.g., CBC mode), how does this feature enhance security?

It ensures any tampering in one block corrupts the decryption of subsequent blocks

By eliminating the need for an initialization vector

It allows blocks to be decrypted independently without error

It doubles the key size automatically

How might a subtle modification to a Trojan horse's code make it especially difficult for antivirus programs to detect?

By using polymorphic or metamorphic techniques to change its signature

By removing the malicious payload entirely

By restricting it to minor operating systems

By using a well-known cryptographic library

During cryptanalysis of a cipher text, you suspect the key length used in a polyalphabetic cipher is quite large. Which method might still be effective in determining the key or plaintext?

Statistical attacks focusing on patterns or repeated segments

Random guessing of all possible transpositions

Using steganography to embed the key

To protect against sophisticated active attacks, an organization implements a layered security model. Which best defines the rationale behind this 'Defense in Depth' strategy?

Using overlapping security measures reduces the likelihood of a single point of failure

Multiple layers are used only to meet compliance requirements

Each security layer is responsible for a unique principle (confidentiality, integrity, etc.)

It focuses only on external threats, ignoring internal vulnerabilities

Information Security model exam

Quiz

•

Computers

•

University

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Practice Problem

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Hard

Thomas Chacko

Used 1+ times

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It is a type of active wiretapping device.

It primarily encrypts data for ransom.

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