Q250
What will be the ciphered text corresponding to "EXAMPLE" if running key cipher is used for encryption with keyword as "DATASTRUCTURE"?
A.
IYUNIFW
AnswerB.
IXVMGJW
C.
HWUNHGW
D.
IZVPIFX
Answer: Option A
Solution
Answer: Option A
Solution:
Running Key Cipher is a polyalphabetic substitution cipher where a plaintext is combined with a keyword to generate a ciphered text. The keyword is usually a long text that matches or exceeds the length of the plaintext.Given:
Plaintext: "EXAMPLE"
Keyword: "DATASTRUCTURE"
Step 1: Convert each letter to its corresponding position in the alphabet:
E = 5, X = 24, A = 1, M = 13, P = 16, L = 12, E = 5
D = 4, A = 1, T = 20, A = 1, S = 19, T = 20, R = 18
Step 2: Add the positions of the plaintext and keyword letters:
(5 + 4), (24 + 1), (1 + 20), (13 + 1), (16 + 19), (12 + 20), (5 + 18)
= 9, 25, 21, 14, 35, 32, 23
Step 3: If the sum exceeds 26, subtract 26 to get the cipher position:
9, 25, 21, 14, 35 - 26 = 9, 32 - 26 = 6, 23
Step 4: Convert these positions back to letters:
9 = I, 25 = Y, 21 = U, 14 = N, 9 = I, 6 = F, 23 = W
Ciphered Text:
The final ciphered text is "IYUNIFW".
Conclusion:
The correct answer corresponds to the following option:
Option A: IYUNIFW