Cochin University of Science and Techology (CUST) 2005-7th Sem B.Tech Information Technology ,, IT 705 (C) Cryptography And Data Security (99 to 01 Ad) - Question Paper

O fStO.VII - OS - 070 (Z)

B. Tec ft. Degree VII Semester Examination, November 260$

IT 705 <C) CRYPTOGRAPHY AND DATA SECURITY

(1999/a 200! AJmisihtns)

O fStO.VII - OS - 070 (Z)

B. Tec ft. Degree VII Semester Examination, November 260$

Time: 3 Hours    Muuma Maifct: 100

Answer iili questions. All Questions carry equal niaxks.

I    ) lixplain liow eryployiaphy ditTcr from coding tltcory .    

b) Suppose that the plaintext "go" conespondslolJteciphercxl^Hlir\ when an Affine    

Cipher uxeslheencrypikm function * -* a** {1 (mod 26). Find the values of a and p.

Assume that (lie letters of the alphabets arc assigned the numbers as follows, abedefghij kl mnopqrsluvwxyz

t I 2 J 5 4 I t It II I) I) l< II It II II I) II )1 U H 1J

OH

II    a) I'ind the atcryiHkfli of the |>lailcxl "input" ond alter'* using tlic encryption function x -

I3* + 4 (mod 26). lUplom liow cryplogr*phy ditTcr from coding theory.

Assume ()ta( (lie letters of (lie alphabets arc assigned (Ik numbers as follows.

a h c d e f g Ii ] j kl mitopqrsl uvwxyx

i t ) s 6 1 i t It II I) I) II II l I! II It K II U 1) II 1)

O fStO.VII - OS - 070 (Z)

B. Tec ft. Degree VII Semester Examination, November 260$

b)    Discum (lie main objectives that arise in information security.    10

c)    Uxplain wlat do you mean by absolute security in cryptography?

III    a) What do you mean by double encryption is equivalent to single encryption? Is this jj

true til Uie case of DF.S?

b) lixplain the usage of Linear l^;eedbockSliift Registers in Ccyptogtophy.    gg

OH

IV h) Discuss on DCS I us begun to stow signs of age'*.

!>) lixplain tlie role of Imile state nmchine hi cryptography.

2

Y it) Deinonstrote how nn NP-conipletc problem can he used Tor puhiic-key cry|>(0gro|)lty.

I>) Dcsciibc iit detail. litc RS A Algorithm wilh an example.

OR

VI a) Explain U>e possible approaches lo altnckuig die RSA olgorKhnv

b) IJcscribein udnil, tl*c public key systems based on elliptic curves wiili an example.

VU a) Ilxplain cfincfent Cryptographic protocol*.

I>) lixplain tiw rule ofllosh function in cryptography. <iive any two I lash function,*.

OH

VIII a) Describe in detail, message autlienticalion with digital signatures.

Ii) lixplain how do wc achicve message integrity whit hash cotin.

IX a) Wluil docs Network Security mean?

Ii) Explain the general 'peels of key management and key dniribution.

OR

X n) Discuss in detail key Agreement protocols.

b) What ore tlte ways to employ Network Security?

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Earning:   Approval pending.