This assignment has two parts. It is due by 5/3/19 at 11:59PM.
There will be late penalty of 5% per day late!
You stumbled upon a GPG key, and an encrypted file called
message.txt.gpg
Your task is to use this key to decrypt the file, and then follow the directions
written inside the file. You must use the command line tools gpg and
openssl for this task, or you will not receive any credit.
You are given an image.
Encrypt this file with AES-128 encryption in ECB mode with this command:
openssl enc -aes-128-ecb -e -in original.bmp -out ecb.bmp -K 00112233445566778899aabbccddeeff
Next, encrypt this file with AES-128 encryption in CBC mode with this command:
openssl enc -aes-128-cbc -e -in original.bmp -out cbc.bmp -K 00112233445566778899aabbccddeeff -iv 00000000000000000000000000000000
Encrypt the image with the AES128 algorithm in ECB mode with the openssl
command line tool, and name it ecb.bmp. Next, encrypt the image with the
AES128 algorithm in the same way but in CBC mode, and call it cbc.bmp. Run
this script in order to patch the headers of both files so
they may be viewed as images, then embed both pictures in your writeup.
Answer these questions:
- What do you notice about both pictures?
- Which block cipher mode is less secure? Why? Explain using information about how the different block cipher modes of operation work.
Make sure to submit all of the code you write, if any!
Your writeup folder should include
- original.bmp
- ecb.bmp
- cbc.bmp
as well as any other particular files mentioned in message.txt.gpg after encrypting and following its instructions. Copy over existing files if necessary.
For Part 1, half credit will be granted for importing the key and showing proof that it is imported to the keychain. Full credit will be granted for additionally following the steps mentioned in the encrypted message.
For Part 2, 10 points will be granted for encrypting the original picture twice and including each file in your writeup, with the correct filenames. 10 points will be granted for answering each question.
Use any available documentation on how to use the commands mentioned in class.
This includes the lecture slides as well as the man pages.