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Feistel Cipher - Cryptography - Exam, Exams of Cryptography and System Security

Jaypee University of Engineering & TechnologyCryptography and System Security

Main points of this past exam are: Feistel Cipher, Popular Cipher, Middle Attack Works, Inadequate, Cipher, Main Factors, Euclidean Algorithm, Parameters, Kocher’S Timing Attack, Theoretical Attack

Typology: Exams

2012/2013

Uploaded on 03/28/2013

mahmud
mahmud 🇮🇳

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Cork Institute of Technology
Bachelor of Science (Honours) in Software Development and Computer Networking - Award
(Bachelor of Science in Software Development and Computer Networking - Award)
Bachelor of Science (Honours) in Software Development with a Language – Award
Bachelor of Science in Software Development with a Language – Award
(NFQ - Level 8)
Summer 2005
Cryptography
(Time: 2 Hours)
Instructions:
Answer any three questions.
Each Question is worth 40 Marks.
Note that 120 Marks = 100%.
Examiners: Dr. D. Chambers
Mr. P. O Connor
Mr. T. Parslow
Mr. V. Ryan
Question 1
(a) Outline the Feistel Cipher. [8 Marks]
Explain why it is a popular cipher upon which many are based.
[5 Marks]
(b) Explain how meet in the middle attack works.
[8 Marks]
(c) Why was DES considered inadequate as a cipher for the last 10 years approximately?
[7 Marks]
(d) Overview the AES cipher.
[6 Marks]
(e) What were the main factors being considered when choosing a cipher as the AES, and why?
[6 Marks]
pf3

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Cork Institute of Technology

Bachelor of Science (Honours) in Software Development and Computer Networking - Award

(Bachelor of Science in Software Development and Computer Networking - Award)

Bachelor of Science (Honours) in Software Development with a Language – Award

Bachelor of Science in Software Development with a Language – Award

(NFQ - Level 8)

Summer 2005

Cryptography

(Time: 2 Hours)

Instructions: Answer any three questions. Each Question is worth 40 Marks. Note that 120 Marks = 100%.

Examiners: Dr. D. Chambers Mr. P. O Connor Mr. T. Parslow Mr. V. Ryan

Question 1 (a) Outline the Feistel Cipher. [8 Marks]

Explain why it is a popular cipher upon which many are based. [5 Marks]

(b) Explain how meet in the middle attack works. [8 Marks]

(c) Why was DES considered inadequate as a cipher for the last 10 years approximately? [7 Marks]

(d) Overview the AES cipher. [6 Marks]

(e) What were the main factors being considered when choosing a cipher as the AES, and why? [6 Marks]

Question 2 (a) Outline the RSA cipher. [5 Marks]

(b) Suppose that RSA is being used. The parameters p , q and e have been chosen as 79 , 89 and 113 respectively. Complete the key generation by finding d. Use the Euclidean Algorithm. [8 Marks]

Encrypt the plaintext 42 using the public key. Use the Fast exponentiation method. [7 Marks]

(c) Outline how and why Kocher’s Timing Attack provides a theoretical attack against RSA. [6 Marks]

It can be thwarted using blinding. Explain how blinding is implemented in both the encryption and decryption processes. [6 Marks]

(d) Why is it that a typical RSA key needs to be of size 1024 bits while an AES key is secure with only 128 bits? [7 Marks]

Question 3 a) Detail the CFB mode of operation for encryption and decryption. [8 Marks]

Detail the strengths and weaknesses of the CFB mode. [7 Marks]

b) Detail the OFB mode of operation for encryption. [5 Marks]

What is the short-cycle problem? Give details. [7 Marks]

What effect does the short-cycle problem have upon how we can use OFB? [5 Marks]

c) When might you use COUNTER mode and why? [8 Marks]