CS Free MCQ Bank

[ Option B ]

The primary advantage of setting up a DMZ (Demilitarized Zone) using a firewall is to create multiple zones of trust within a network, which enhances security. A DMZ acts as a buffer zone between the public Internet and the internal private network, isolating public-facing servers (such as web, email, and DNS servers) from sensitive internal resources. This setup allows external users to access services in the DMZ while preventing direct access to the internal network.

[ Option D ]

[ Option B ]

The SHA-2 (Secure Hash Algorithm 2) family is a set of cryptographic hash functions designed to provide secure hashing for data integrity and digital signatures. 
SHA-2 includes variants such as SHA-224, SHA-256, SHA-384, and SHA-512, where the number in the name indicates the length of the hash output in bits.
SHA-256, the most commonly used variant, produces a 256-bit (32-Byte) hash value.

[ Option C ]

Data Encryption Standard (DES) is a symmetric key block cipher widely used for secure data transmission. 

• In DES, the input block size is 64 bits, meaning the plaintext is divided into 64-bit blocks before encryption. 
• The key size is 56 bits, although the original key is 64 bits long, 8 bits are used for parity and do not contribute to the actual encryption. 
• The output block size is also 64 bits, so each 64-bit plaintext block is transformed into a 64-bit ciphertext block. 

This design allows secure encryption and decryption using the same 56-bit key.
 

[ Option A ]

By default, IIS (Internet Information Services) allows users to access web content without requiring credentials. This is called Anonymous Authentication, where the server uses a built-in account to handle requests from unauthenticated users.

[ Option B ]

Data Encryption Standard (DES) is a Symmetric Key block cipher algorithm that uses the same secret key for both encryption and decryption.

• In DES, the input block size is 64 bits, meaning the plaintext is divided into 64-bit blocks before encryption. 
• The key size is 56 bits, although the original key is 64 bits long, 8 bits are used for parity and do not contribute to the actual encryption. 
• The output block size is also 64 bits, so each 64-bit plaintext block is transformed into a 64-bit ciphertext block. 

The encryption process in DES consists of a series of operations known as rounds. In DES total 16 rounds are performed, making the encryption much stronger and harder to break through Brute-Force or Statistical Attacks.

[ Option A ]

Given, Plaintext = SACKGAUL, but it says read from right to left, so we reverse it: LUAGKCAS. Now, the positions are:

[ Option D ]

Fabrication refers to creating fake messages or data, so authentication mechanisms are used to detect and prevent this.
Modification means altering messages during transmission. Ensuring message integrity detects such tampering.
Interception refers to unauthorized access or eavesdropping. Confidentiality (encryption) protects the message content.

[ Option A ]

Secure Hash Algorithm-1 (SHA-1) produces a message digest of 160 bits (20 bytes). SHA-1 takes an input of any length (less than 264 bits) and outputs a fixed-length hash value of 160 bits. This hash value, called the message digest, is used for data integrity verification, digital signatures, and other cryptographic applications.

[ Option D ]

A Honeypot is a security mechanism used in Intrusion Detection Systems (IDS) to attract attackers and study their behavior. It is designed to look like a real system containing valuable data or services, but it is actually a Decoy that isolates and monitors malicious activities. 

Honeypots help in diverting attackers’ attention away from critical systems and collecting information about their methods, tools, and intentions. 
However, Legitimate Users are not supposed to know about or access honeypots, as their purpose is purely for monitoring and deception.

[ Option C ]

Symmetric key algorithms use the same key for encryption and decryption. RC4, Blowfish, and DES (Data Encryption Standard) are examples of symmetric key cryptography algorithms.
Diffie-Hellman is a key exchange algorithm and is part of asymmetric key cryptography, used to securely exchange cryptographic keys over a public channel. It is not an encryption algorithm itself.

[ Option D ]

A Proxy Firewall filter works at the Application Layer of the OSI model. It acts as an intermediary between a client and a server, intercepting all requests and responses.

[ Option A ]

A plain text message can be hidden or protected in two main ways.
Steganography is a technique used to hide secret messages or data within another file, such as an image, audio, or video, in such a way that its existence is not apparent to others. 
For example, a confidential message can be hidden inside the pixel values (modifying the Least Significant Bits (LSBs) of the Pixels) of an image file without noticeably changing the image itself.

Cryptography transforms plaintext into ciphertext via encryption, rendering the content unintelligible to outsiders without the decryption key.

[ Option A ]

In RSA encryption, we are given P = 7, Q = 17, public key e = 5, and plaintext M = 10.
First, calculate n = P × Q = 7 × 17 = 119 and φ(n) = (P - 1) × (Q - 1) = 6 × 16 = 96.
The public key pair is therefore (5, 119). Using the encryption formula C = M^e mod n, we get C = 10⁵ mod 119 = 40.