Introduction to Cryptography with Open-Source Software

Introduction to cryptography 21

(a) encrypt THIS IS A SECRET MESSAGE

(b) decrypt MDQHBOEOIZZEPZGDFE

15. Suppose the Bifid cipher was applied to two characters of the plaintext

at a time, rather than to the entire plaintext. How does this differ from

the P layfair cipher?

16. Use the Playfair cipher with keyword ENCRYPT to

(a) encrypt SELL MY CAR

(b) decrypt PX CD QU ML AM YH

17. Use the Playfair cipher with keyword SURFING to

(a) encrypt MOVE NORTH TONIGHT

(b) decrypt UD DM OP UH OP GD ZY

18. Use the ADFGVX cipher with the array given on page 17 and the key-

word ENCRYPT to

(a) encrypt GO SOUTH

(b) decrypt AVAV VXXD VAVD VXDX VDVX GVFV GXXF

19. Use the ADFGVX cipher with the array given on page 17 and the key-

word CODE to

(a) encrypt BRING A FRIEND

(b) decrypt ...