I. Exercise 1, Chapter 2. Describe each of the following three(3) kinds of acces

Question

I. Exercise 1, Chapter 2. Describe each of the following three(3) kinds of access control mechanism in terms of i. ease of determining authorized access during execution ii. ease of adding access for a new iii. ease of deleting access by a user iv. ease of creating a new object (file, program, database, etc.) which all users have, user by default, access. Access control mechanisms: per-user access control lists - one list for each user determinines all the objects the user has access to. e. f per-object access contol list-each object has a list of users who have access. g. access control matrix. I. Exercise 11, Chapter 2. Outline the design of an authenitication scheme that "learns". The scheme would initially have some information about a user -e.g. the username and password. As the use of the computing system continued, the authentication system would "gather" additional information, e.g. programming languages used, dates and times of use, etc. The authentication requirements would become more personalized with time. List the the types of information the system could gather. Assume that the authentication scheme is for a laptop or a phone. Consider how the authentication information would be presented and validated. Does the user answer true/false or multiple choice questions. Does the system need to interpret natural language prose? . a. III. Research the Advanced Encryption Standard on-line. What key lengths are used today for TOP SECRET government usage? When did the National Security Agency decide that AES could be used to encrypt classified documents? a. b. Describe one-type of attack against AES

Explanation / Answer

Answer for No. III :-

. 192 or 256 key lengths are used today for TOP SECRET government usage.

a. National Security Agency decided on June, 2003 that AES could be used to encrypt classified documents.

b. One of best know attack against AES is Meet-in-the-Middle(MITM) cryptanalysis for both AES-192 and AES-256. This attack apply on following circumstances :-

In this attack, Attacker require plaintext and corresponding ciphertext pair. Then, he/she divide ciphertext into two subciphers and compute all possible middle states to find a correct key-pair. This method can be further enhanced using biclique structure/complete bipartite graph consisting of two groups vertices and each vertex of one group is connected to all vertex of other.

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