Unit $2$ Stream Ciphers

Skills and elements used

Ciphers, XOR, boolean algebra, modular arithmetic

$1)$ Why is the exclusive or operation important in cryptography?

$2)$ What is the result of $110101$ XOR $011010?$

$3)$ What is the result of $1011001$ XOR $1100101$

$4)$ The ciphertext $($C$)$ below was created by XORing a plain text ASCII message with the key $($K$).$ Decode the message, show the resulting bits, and lookup the ASCII codes to recover the plaintext message.

K: $101011111011010001011010$

C: $111110111111011100011001$

$5)$ Why is a simple XOR cipher not a practical choice for general encryption?

$6)$ Describe the three types of random number generators and how they differ.

$7)$ The following LSFR has initial sequence $101,$ compute all its outputs until the bits begin to repeat.

Z$0=101$

Z$2=$

Z$3=$

Z$4=$

Z$5=$

Z$6=$

Z$7=$

Z$8=$