The Decryption Process

• To decrypt the encrypted message it must be xor'ed with the same random sequence that was used for encryption.
  

  SYN	NULL	h	N	ETX	a	[
  16x	00x	68x	4Ex	03x	61x	5Bx
  0010110	0000000	1101000	1001110	0000011	1100001	1011011
  			$\oplus$
  1010011	1000011	0101101	1101110	0110010	1010001	1101010
  			=
  1000101	1000011	1000101	0100000	0110001	0110000	0110001
  45x	43x	45x	20x	31x	30x	31x
  E	C	E	SPACE	1	0	1

• Fundamentally, this works because
  • $0 \oplus 0 = 0$ and $1 \oplus 1 = 0$
  • $x \oplus 0 = x$, for x=0 or x=1.
• Problems: How do we find the random sequence?
• How do transmitter and receiver agree on the same sequence?