XOR Encryption Challenges (NETLAB)

Challenge 1: Decrypting a Text File Without the Key

This one is pretty simple: the key is a capital letter, from A to Z.

To get the ciphertext, execute this command: 

wget http://samsclass.info/xorchal1-cipher
Decrypt the file. When you get it, capture a whole-desktop image showing the contents, which begin with "Congratulations", as shown below:

Save the image as "Proj 13xa from YOUR NAME".

Challenge 2: Decrypting a Text File Without the Key

The key is a single byte from \x00 to \xff.

To get the ciphertext, execute this command: 

wget http://samsclass.info/xorchal2-cipher
Decrypt the file. When you get it, capture a whole-desktop image showing the contents, which begin with "Congratulations", as shown below:

Challenge 3: Decrypting an Image File Without the Key

The key is a single byte from \x00 to \xff.

To get the ciphertext, execute this command: 

wget http://samsclass.info/xorchal3-cipher
This is an image file. When decrypted, it starts with a PNG file header, as shown below:

Notice that the first 4 bytes are 89, 50, 4E, 47; the 2nd through 4th byte spell out PNG in ASCII.

Decrypt the file. When you get it, change its filename extension to PNG and open it in an image viewer or Web browser.

Challenge 4: Decrypting an Image File Without the Key

The key is two bytes from \x0000 to \xffff.

To get the ciphertext, execute this command: 

wget http://samsclass.info/xorchal4-cipher
This is an image file. When decrypted, it starts with a JPEG file header, as shown below:

Notice that the first 2 bytes are FFD8, and some later bytes contain the ASCII characters JFIF.

Decrypt the file. When you get it, change its filename extension to JPG and open it in an image viewer or Web browser.

The image should be visible.

Last revised: 8-17-15

Revised for NETLAB 6-13-16