## XOR Challenge

#### Problem

Sorting through your emails, and deleting the abundance of junk mail that seems to arrive on a daily basis, your attention is drawn to one particular mail:

----- Original Message -----
To: mastermind@coolmail.co.uk
Sent: Saturday, March 1, 2003 1:00 AM
Subject: Only the best need try...

Hi mastermind

So you think you're good at code breaking? I'll tell you how I encoded the message and all you need to do is decode it!

I started by using the table below to change the message into a binary string, then XOR"ed it with the alternating string 101010101..., finally I converted it back into readable text. I guess you'll have to research how XOR works. ;)

Here's the table:

 Bin Chr Bin Chr Bin Chr Bin Chr 00000 spc 01000 H 10000 P 11000 X 00001 A 01001 I 10001 Q 11001 Y 00010 B 01010 J 10010 R 11010 Z 00011 C 01011 K 10011 S 11011 . 00100 D 01100 L 10100 T 11100 , 00101 E 01101 M 10101 U 11101 ? 00110 F 01110 N 10110 V 11110 ! 00111 G 01111 O 10111 W 11111 -

Here's the encoded message:

,GEXPYFCCOK

Good luck!
mathschallenge.net

Can you decode the message?

Problem ID: 1 (Aug 2000)     Difficulty: 3 Star

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