LAB3-INSTRUCTIONS

Lab 3 : CEG 3400

Encryption

Table of contents:

• Background
• Objectives
• Preparation
• Task 1: Symmetric Encryption
• Task 2: Asymmetric Encryption
• Task 3: Encrypted Email
• Task 4: Digital Signatures

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Background

Encryption is a basic tool for securing data at rest and data being sent across unsecure channels.

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Objectives

Become familiar with several symmetric and asymmetric encryption protocols.

Analyze how well some encryption protocols secure data versus others.

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Preparation

These commands will likely need a full version of bash as found in WSL Ubutun or other linux distro. The default shell provided by MobaXTerm does not support several of the needed programs. Be sure you can run all needed commands before getting stuck partway through ;)

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Task 1 - Symmetric Encryption

In this task you will encrypt a simple image using different encryption modes and analyze the effectiveness of each mode. A list of all the supported algorithms and modes are found in the openssl and enc man pages.

Encrypt the data/example_pic.bmp file with the aes-128 algorithm using each of the following encryption modes

• aes-128-cbc, aes-128-ecb, and aes-128-ofb – total of 3 ciphertext files created. Name the files example_pic.cbc, example_pic.ecb, and example_pic.ofb. Make up an easy to remember encryption password when prompted (e.g. 12345).

The general form of the encryption command is as follows:

openssl  <ALGORITHM_MODE>  -e  -in  <INPUT_FILE>   -out  <OUTPUT_FILE>

When you encrypt these images, you also encrypt the header information needed to open them in an image viewer. In order to view the encrypted files you will need to recreate the standard header format of a .bmp file before an image viewer will recognize the encrypted data as an image.

The needed header data is stored in the first 54 bytes of every .bmp file. You can cut it out and save it with the following command: dd if=example_pic.bmp of=bmp_header.hex bs=1 count=54 but I did this already and provided the header data in data/bmp_header.hex.

To prepend this to your cypher text simply use the cat command as follows:

cat data/bmp_header.hex ./example_pic.ofb > ofb.bmp

Once you have done this with all three files open them in an image viewer and compare them to the original image and each other. Write your finding in README.md

10 points of your grade are given simply for embedding all three encrypted images in your README.md

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Task 2 - Asymmetric Encryption

It's really simple, using the instructor's public key provided in class, encrypt this file (the LAB3-INSTRUCTIONS.md file.).

Name this file task2.enc (you may need to use the mv command to rename it after creation) and upload task2.enc to your lab 3 github repository. Answer all task 2 questions in the README.md.

Hints: To encrypt a message or file using gpg you need to specify a recipient email address that you have the corresponding public key. I am intentionally not giving the full command so you can play around with gpg, you might need to use the man command (and/or google).

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Task 3 - Encrypted Email

This task is very straightforward. Send an encrypted email to matthew.kijowski@wright.edu from your campus email address.

To: matthew.kijowski@wright.edu
From: <youremail@wright.edu>

Subject: Task 3 - Thunder

Body: <whatever you would like, only I can read it>

• Download Thunderbird
• Add your Wright State email account to Thunderbird:
• Thunderbird now recognizes your @wright.edu email and should take you to the WSU login page. If not needed settings are below:
• IMAP settings
  • Server name: outlook.office365.com
  • Port: 993
  • Encryption method: TLS
  • Authentication method: OAuth2
• SMTP settings
  • Servername: smtp.office365.com
  • Port: 587
  • Encryption method: STARTTLS
  • Authentication method: OAuth2

Once you can send and recieve mail in thunderbird using your @wright.edu email set up encryption:

• In Thunderbird settings click on the account you want to set up (@wright.edu) > End-To-End Encryption
  • Add your GPG secret key
    • You can retrieve it from gpg --export-secret-keys <youremail@wright.edu> > your-secret-key.gpg
  • Open the OpenPGP Key Manager and import my public key (and anyone else's you want to have secure communications with)

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Task 4 - Digital Signatures

For this task you will be applying a digital signature to your README.md (using the gpg command, not thunderbird). This must be done AFTER you are done answering all questions (don't edit the README.md after signing) . If you do need to edit README.md after you sign it, simply delete the signature at the end and re sign it.

Hint: There are multiple ways to digitally sign a document with gpg. Use the --clearsign option.