Quadratic Ciphers - Introduction to Cryptography with Java Applets - page 211

of 1 consists entirely of small factors. Also, as with Rabin, Blum-Goldwasser is vul-

nerable to a chosen ciphertext attack. You should consider how such an attack may be posed.

p

EXERCISES

1. Use Rabin to encipher the following messages:

a. TORPEDO AWAY

b. FIRE AT WILL

c. WILL GONE BELAY MY LAST

Use = 10859, and the ordinary alphabet. Use a tagging scheme for the sake

of decryption. Block and pad as necessary, but do not use salt. Then decipher.

= 11027,

p q

2. Explain how Blum-Goldwasser probabilistic encryption is vulnerable to a chosen

ciphertext attack.

3. Write a Java program to execute a chosen ciphertext attack on Rabin.

4. Write a Java program to execute a square root attack on an unsalted enciphered mes-

sage sent to multiple recipients using the Rabin transformation.

5. Write a rabinEncipherWCBC() method and a rabinDecipherWCBC() method for the

Ciphers class.

6. Write enciphering and deciphering methods for the Blum-Goldwasser cipher.