# How can a XOR encryption be cracked systematically?

It's given that a string, encoded in hex format, is obtained by XOR encryption of a plain text and a key. The key is unknown (not even the length). What are the steps that I should follow to get the plain text? Since I am new to this, I am unaware of the tools to be used.

Example: Crack the following hex encoded string, obtained by XOR cipher:
000000003f2537257777312725266c24207062777027307574706672217a67747374642577263077777a3725762067747173377326716371272165722122677522746327743e

PS: I know that by applying XOR on the cipher text with the key will give me back the plain text. How should I proceed, if I don't know the key?

• please see, one-time pad – kelalaka Sep 28 '18 at 9:24
• Note that - specific to this question - the key and plaintext start with the same byte values: that's the only way that the first bytes can be zero after all. The key is most likely binary, not hexadecimal. Hexadecimals can be used to represent binary values. – Maarten Bodewes Oct 1 '18 at 15:02