MCA5042- Cryptography and Network Security

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[ WINTER, 2015 ] ASSIGNMENT

PROGRAM	MCA(REVISED FALL 2012)
SEMESTER	V
SUBJECT CODE & NAME	MCA5042- Cryptography and Network Security
CREDIT	4
BK ID	B2069
MAX. MARKS	60

Answer all the Questions

Question.1. Define computer security. Explain the important objectives of computer security.

                                                                                                                    

Answer:Computer security, also known as cybersecurity or IT security, is the protection of information systems from theft or damage to the hardware, the software, and to the information on them, as well as from disruption or misdirection of the services they provide. It includes controlling physical access to the hardware, as well as protecting against harm that may come via network access, data and code injection,and due to malpractice by operators, whether intentional, accidental, or due to them being tricked into deviating from secure procedures.

The field is of growing importance due to the

Question.2. Explain Feistel Cipher.

Answer:In cryptography, a Feistel cipher is a symmetric structure used in the construction of block ciphers, named after the German-born physicist and cryptographer Horst Feistel who did pioneering research while working for IBM (USA); it is also commonly known as a Feistel network. A large proportion of block ciphers use the scheme, including the Data Encryption Standard (DES). The Feistel structure has the advantage that encryption and decryption operations are very similar, even identical in some cases, requiring only a reversal of the key schedule. Therefore the size of the code or circuitry required to implement such a

Question.3. Explain the following.

(a) Asymmetric Keys

Answer:An asymmetric algorithm, as outlined in the Diffie-Hellman paper, is a trap door or one-way function. Such a function is easy to perform in one direction, but difficult or impossible to reverse. For example, it is easy to compute the product of two given numbers, but it is computationally much harder to find the two factors given only their product. Given both the product and one of the

(b) Public Key Certificate

Answer:Asymmetric cryptography or public-key cryptography is cryptography in which a pair of keys is used to encrypt and decrypt a message so that it arrives securely. Initially, a network user receives a public and private key pair from a certificate authority. Any other user who wants to send an encrypted

(c) Public Key (Asymmetric) Cryptographic Algorithm

Answer:Public-key cryptography refers to a set of cryptographic algorithms that are based on mathematical problems that currently admit no efficient solution -- particularly those inherent in certain integer factorization, discrete logarithm, and elliptic curve relationships. It is computationally easy for a user to

(d) Public Key Infrastructure (PKI)

Answer:A public key infrastructure (PKI) is a set of hardware, software, people, policies, and procedures needed to create, manage, distribute, use, store, and revoke digital certificates and manage

Question.4. (a) Explain digital signature.

Answer: A digital signature is a mathematical scheme for demonstrating the authenticity of a digital message or documents. A valid digital signature gives a recipient reason to believe that the message was created by a known sender, that the sender cannot deny having sent the message (authentication and non-repudiation), and that the message was not altered in transit (integrity). Digital signatures are commonly used for software distribution, financial transactions, and in other cases where it is important to detect forgery or tampering.

(b) Explain the different types of attacks on digital signatures.

Answer:In their foundational paper, Goldwasser, Micali, and Rivest lay out a hierarchy of attack models against digital signatures:

·         In a key-only attack, the attacker is only given the public verification key.

·         In a known message attack, the attacker is given valid signatures for a variety of messages known by the attacker but not chosen by the attacker.

·         In an adaptive chosen

Question.5. Explain the Benefits of IP security.

Answer:Internet Protocol Security (IPSec) is a framework of open standards for ensuring private, secure communications over Internet Protocol (IP) networks, through the use of cryptographic security services. IPSec is a suite of cryptography-based protection services and security protocols. Because it requires no changes to programs or protocols, you can easily deploy IPSec for existing networks.

The driving force for the acceptance and deployment of secure IP is the need for business and government users to connect their

Question.6. Define the following terms used in the IEEE 802.11 standard.

(a) Access point (AP)

Answer:In computer networking, a wireless access point (WAP) is a networking hardware device that allows wireless devices to connect to a wired network using Wi-Fi, or related standards. The AP usually connects to a router (via a wired network) as a standalone device, but it can also be an integral component of the router itself. An AP is differentiated from a hotspot, which is the physical space where

(b) Basic service set (BSS)

Answer: Basic Service Set is a component of the IEEE 802.11 WLAN architecture. This network architecture is built around a Basic Service Set (BSS), which is actually a set of STAs (the component that connects to the wireless medium such as a network adapter or NIC) that communicate with each other. When one access

(c) Coordination function

Answer:Distributed coordination function (DCF) is the fundamental MAC technique of the IEEE 802.11 based WLAN standard. DCF employs a CSMA/CA with binary exponential backoff algorithm.

DCF

(d) Distribution system (DS)

Answer:A wireless distribution system (WDS) is a system enabling the wireless interconnection of access points in an IEEE 802.11 network. It allows a wireless network to be expanded using multiple access points

(e) Extended service set (ESS)

Answer:An extended service set (ESS) is one or more interconnected basic service sets (BSSs) and their associated

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