Unit 1

In brute force attack, on average half of all possible keys must be tried to achieve success

• True

• False

If the sender and receiver use different keys, the system is referred to as conventional cipher system

• True

• False

Use Caesar’s Cipher to decipher the following HQFUBSWHG WHAW

• ABANDONED LOCK

• ENCRYPTED TEXT

• ABANDONED TEX

• ENCRYPTED LOCK

Which are the most frequently found letters in the English language ?

• e,a

• e,o

• e,t

• e,i

Choose from among the following cipher systems, from best to the worst, with respect to ease of decryption using frequency analysis.

• Random Polyalphabetic, Plaintext, Playfair

• Random Polyalphabetic, Playfair, Vignere

• Random Polyalphabetic, Vignere, Playfair, Plaintext

• Random Polyalphabetic, Plaintext, Beaufort, Playfair