Purchase Solution

Network security

Not what you're looking for?

Ask Custom Question

I need detailed answers for these 2 questions.

1.Suppose we wish to use Kerberos for securing electronic mail. The obvious way of accomplishing this is for Alice, when sending a message to Bob, to obtain a ticket for Bob and include that in the email message, and to encrypt and/or integrity-protect the email message using the key in the ticket. The problem with this is that then the KDC would give Alice a quantity encrypted with Bob's password-derived master key, and then Alice could do off-line password guessing. How might Kerberos be extended to secure email without allowing off-line password guessing?
(Hint: Issue human users an extra, unguessable master key for use with mail, and extend the Kerberos protocol to allow Bob to safely obtain his unguessable master key from the KDC.)

2.Assume we are using secret key technology. What is wrong with the following source authentication scheme?
Alice chooses a per-message secret key K, and puts an encrypted version of K in the header for each recipient, (ie Bob and Ted). Next, Alice uses K to compute a MAC on the message, say a DES-CBC residue, or to compute a message digest of K and append it to the message.

(Hint: this works fine for a single recipient, but there is a security problem if Alice sends a multiple-recipient message. Once they receive the message, Bob and Ted know both K and K encrypted with the key they share with Alice. This allows either to forge a message to the other as if it were from Alice.)

Purchase this Solution

Solution Summary

Network security is demonstrated.

Purchase this Solution

Free BrainMass Quizzes
C# variables and classes

This quiz contains questions about C# classes and variables.

Javscript Basics

Quiz on basics of javascript programming language.

Word 2010: Tables

Have you never worked with Tables in Word 2010? Maybe it has been a while since you have used a Table in Word and you need to brush up on your skills. Several keywords and popular options are discussed as you go through this quiz.

C++ Operators

This quiz tests a student's knowledge about C++ operators.

Excel Introductory Quiz

This quiz tests your knowledge of basics of MS-Excel.