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Home Work 3

CSE404 : INFORMATION SECURITY & PRIVACY

Part A

Q:-1 Write the differences between trusted and un-trusted networks with suitable examples.

Sol. Trusted networks:

Such Networks allow data to be transferred transparently. The machines using a trusted

network are usually administered by an Administrator to ensure that private and secured data

is not leaked. Access to this network is limited. Computers using trusted networks are more

secured and confidential because of strong firewalls.

Untrusted networks:

Such networks are usually administered by the owners. They can allow improper access tosensitive or personal data. These machines are usually separate. Such machines could me

more prone to attacks.

Trusted network is an open architecture for Network Access Control. The aim is toenable operators of network for providing endpoint integrity at each every networkconnection, which provides interoperability.

Untrusted Networks are controlled and configured by their owners. It could causeimproper access to sensitive data. For this reason the systems are isolated on aseparate sub-net and not allowed a direct access too many computer services.

Q:-2 Give real life examples to demonstrate the applications of cryptography.

Sol. Cryptography is best known as a way of keeping the contents of a message secret.

Confidentiality of network communications, for example, is of great importance for e-

commerce and other network applications. However, the applications of cryptography go far

beyond simple confidentiality. In particular, cryptography allows the network business and

customer to verify the authenticity and integrity of their transactions. If the trend to a global

electronic marketplace continues, better cryptographic techniques will have to be developed

to protect business transactions.

Sensitive information sent over an open network may be scrambled into a form that cannot beunderstood by a hacker or eavesdropper. This is done using a mathematical formula, known

as an encryption algorithm, which transforms the bits of the message into an unintelligible

form. The intended recipient has a decryption algorithm for extracting the original message.

There are many examples of information on open networks, which need to be protected in

this way, for instance, bank account details, credit card transactions, or confidential health or

tax records. Cryptography is no longer the province of a specialized elite of mathematicians

and military operatives. Its potential cost-effective applications to modern

computer/communications systems .

Q:-3 Explain the concept of network security in detail.

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Q:-4 Explain the concept of digital signatures with suitable example.

Sol. q4Hash value of a message when encrypted with the private key of aperson is his digital signature on that e-Document.Digital Signature of aperson therefore varies from document to document thus ensuringauthenticity of each word of that document. As the public key of thesigner is known, anybody can verify the message and the digital signatureprovide Authenticity, Integrity and Non-repudiation to electronicdocuments. To use the Internet as the safe and secure medium for e-Commerce and e-Governance Each individual generates his own key pairPublic key known to everyone & Private key only to the owner.

Public Key Used to verify the digital signature.Private Key Used for making digital signature.

Q:-5 Give the difference between symmetric and asymmetric cryptography with suitable

examples.

Sol. Symmetric-Crypto used techniques are DES, 3DES, AES

smaller keys / faster encryption because of simpler operations (e.g.discrete log) Key agreement problem, Online, Efficient. same key used forencryption and decryption.

Symmetric ciphers

Main problem: key distribution

Symmetric ciphers can be devided into

stream ciphers and block ciphers

Asymmetric-Crypto used techniques are RSA, ECC

1000x slower than DES, more complicated operations (e.g. modularexponentiation)

RSA different key is usedfor encryption and decryption.Decryption key cannot be derivedfrom encryption key.

Asymmetric ciphers

Said to be the most significant new development in cryptography in the last 300-400 years

first described publicly by Hellman and Diffie in 1976

The encryption key is public, decryption key secret

anyone can encrypt a message but only the one who bknows the corresponding private key

can decrypt it.

In practise asymmetric and symmetric algorithms are often used together, called hybrid

encryption

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Q:-6 What is the role of cryptography in information security?

Sol. The protection of information in potentially hostile environments is a crucial factor in

the growth of information-based processes in industry, business, and administration.

Cryptography is a key technology for achieving information security in communications,

computer systems, electronic commerce, and, more generally, in the emerging information

society. means protecting information and information systems from unauthorized access,

use, disclosure, disruption, modification, perusal, inspection, recording or destruction.

Computer security can focus on ensuring the availability and correct operation of a computer

system without concern for the information stored or processed by the computer.

Cryptography provides information security with other useful applications as well including

improved authentication methods, message digests, digital signatures, non-repudiation, and

encrypted network communications. Information security uses cryptography to transform

usable information into a form that renders it unusable by anyone other than an authorized

user; this process is called encryption. Information that has been encrypted (rendered

unusable) can be transformed back into its original usable form by an authorized user, who

possesses the cryptographic key, through the process of decryption. Cryptography is used ininformation security to protect information from unauthorized or accidental disclosure while

the informationis in transit (either electronically or physically) and while information is in

storage .

http://en.wikipedia.org/wiki/Non-repudiationhttp://en.wikipedia.org/wiki/Cryptographyhttp://en.wikipedia.org/wiki/Encryptionhttp://en.wikipedia.org/wiki/Key_(cryptography)http://en.wikipedia.org/wiki/Informationhttp://en.wikipedia.org/wiki/Informationhttp://en.wikipedia.org/wiki/Cryptographyhttp://en.wikipedia.org/wiki/Encryptionhttp://en.wikipedia.org/wiki/Key_(cryptography)http://en.wikipedia.org/wiki/Informationhttp://en.wikipedia.org/wiki/Non-repudiation