kindly reply soon

Question

Q-> what will the cipher text produced by the following cipher function for the plain test ISRO with key =7.[consider 'A'=0,'B'=1...'Z'=25]

C_K(M)=(kM+13)mod26

a)RJCH

b)QIBG

c)GQPM

d) XPIN

Answer 1

Cipher text for ISRO will be RJCH i.e. Option a), which I calculated as follow : A maps to 0,B maps to 1,....., I maps to 8,..., Z maps to 25. Now given k = 7, and c(m) =( k.p(m)+13) mod26 c(I) =( 7x8+13)mod26 c(I) =(56+13)mod26 c(I) =69mod26=17 Now since 17 corresponds to R so c(I) = R. Similarly you can do for S,R and O.

Comments

y u consider I y not m??? please say

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M is not the letter here that we want to convert into cypher text but it is just an abbreviation for the Message/Plain text that we are going to input to this function. For example: F(x) = 2x then if want to know output of the function for input 2 then we put 2 in the place of x to get F(2) i.e. 4. Since the input is already given which is ISRO so we have to consider only I,S,R and O to convert them into their respective cipher text and not M.

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thank you ... :)

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yw! :)