Question

What will be the ciphered text if the string “SECRET” is given as input to the code of autokey cipher with keyword as “SANFOUNDRY”?

(a) KEPWSN

(b) EKWPSN

(c) EKWPSNFDED

(d) KEPWSNFDED

I had been asked this question in an interview for job.

Origin of the question is Cryptography in division Cryptography of Data Structures & Algorithms II

Answer 1

Correct option is (a) KEPWSN

For explanation: For encrypting a plain text in autokey cipher we first add the keyword at the beginning of the plain text in order to obtain the key for encryption. Then we use the vigenere table for making respective substitutions.