CS6701 CNS Important Questions, Cryptography & Network Security Answer Key – CSE 7th SEM Anna University

Anna University Regulation 2013 Computer Science & Engineering (CSE) CS6701 CNS Important Questions for all 5 units are provided below. Download link for CSE 7th SEM CS6701 Cryptography & Network Security Answer Key is listed down for students to make perfect utilization and score maximum marks with our study materials.


1 Differentiate between Active attacks and Passive Attacks

2 Define Steganography.

3 Quote Euler’s theorem.

 4 Define cryptanalysis.

5 Compare Substitution and Transposition techniques.

 6 Analyse why Random numbers are used in Network Security

 7 List the four categories of security threats

 8 Solve 117 mod 13.

9 Define primitive root.

10 Giveexamples for substitution cipher.

11 Define cryptography

12 Explain why Modular arithmetic has been used in cryptography.

13 Compare Block and Stream cipher.

14 Classify the basic functions used in encryption algorithms.

 15 Describe security mechanism.

16 Assess the following cipher Text using brute force attack: CMTMROOEOORW (Hint: Algorithm-Rail fence)

17 Generalize why network need security.

18 Give examples for transposition cipher.

19 Show how to convert the given text “VALLIAMMAI” into cipher text using Rail fence Technique.

20 Plan how many keys are required by two people to communicate via a cipher.


1 State and Describe (i) Fermat’s theorem (8)

(ii) Eular’s theorem(8)

2 (i) Tabulate the substitution Techniques in detail (8) (ii) Describe the Transposition Techniques in detail (8)

3 (i) List the different types of attacks and explain in detail.(8) (ii) Describe Chinese remainder theorem with example. (8)

4 (i) Evalute 321 mod 11 using Fermat’s theorem. (4) (ii) Find GCD using Eular’s Theorem with Example. (6)

(iii) Find GCD of 1070 and 1066 using Euclid algorithm. (6)

5 (i)Encrypt the message “PAY” using hill cipher with the following key matrix and show the decryption to formulate original plain text(8)

K= |17 17 5| |21 18 21| |2 2 19|

(ii)Generalize the security services classifications and security mechanisms in detail.(8)

6 Summarize the following in detail (i) Modular Exponentiation (8) (ii) Finite fields (8)

7 (i) Apply Caesar cipher and k=5 decrypt the given Cipher text “YMJTYMJWXNIJTKXNQJSHJ”. (8) (ii) ApplyVigenerecipher, encrypt the word “explanation” using the key “leg”. (8)

8 (i) Discuss briefly the Discrete Algorithms. (8) (ii) Discuss about the Groups, Rings and Field (8)

9 Differentiate between transposition cipher and substitution cipher. Apply two stage transpositions Cipher on the “treat diagrams as single units” using the keyword “sequence”.

10 (i)What is Steganography? Briefly examine any three techniques used. (8) (ii)What is mono-alphabetic cipher? Examine how it differs from Caesar cipher? (8)

11 Solve using play fair cipher. Encrypt the word “Semester Result” with the keyword “Examination”. List the rules used.

12 (i) With a neat block diagram, explain the network security model and the important parameters associated with it.(8)

(ii) Differentiate active and passive security attacks. Categorize these attacks and explain one examples of each (8)

13 (i) Explain how to solve x2 ≡1(mod 35) using Chinese remainder theorem. (8) (ii) Explain in detail the Euclid’s Algorithm. (8)

14 (i) Discuss the following a) Message Integrity (2) b) Denial of Service (2) c) Availability (2) d) Authentication (2)

(ii) Estimate 1113 mod 53 using modular exponentiation. (8)

CS6701 CNS All units Important Questions  Download Here

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For CS6701 CNS Question Bank/2marks 16marks with answers – Click here

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CS6701 Cryptography & Network Security Answer Key free download

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CS6701 Answer Key, CNS Unit wise Important Questions- CSE 7th Semester



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