\[ \begin{align}\begin{aligned}\newcommand\blank{~\underline{\hspace{1.2cm}}~}\\% Bold symbols (vectors) \newcommand\bs[1]{\mathbf{#1}}\\% Differential \newcommand\dd[2][]{\mathrm{d}^{#1}{#2}} % use as \dd, \dd{x}, or \dd[2]{x}\\% Poor man's siunitx \newcommand\unit[1]{\mathrm{#1}} \newcommand\num[1]{#1} \newcommand\qty[2]{#1~\unit{#2}}\\\newcommand\per{/} \newcommand\squared{{}^2} \newcommand\cubed{{}^3} % % Scale \newcommand\milli{\unit{m}} \newcommand\centi{\unit{c}} \newcommand\kilo{\unit{k}} \newcommand\mega{\unit{M}} % % Percent \newcommand\percent{\unit{\%}} % % Angle \newcommand\radian{\unit{rad}} \newcommand\degree{\unit{{}^\circ}} % % Time \newcommand\second{\unit{s}} \newcommand\s{\second} \newcommand\minute{\unit{min}} \newcommand\hour{\unit{h}} % % Distance \newcommand\meter{\unit{m}} \newcommand\m{\meter} \newcommand\inch{\unit{in}} \newcommand\foot{\unit{ft}} % % Force \newcommand\newton{\unit{N}} \newcommand\kip{\unit{kip}} % kilopound in "freedom" units - edit made by Sri % % Mass \newcommand\gram{\unit{g}} \newcommand\g{\gram} \newcommand\kilogram{\unit{kg}} \newcommand\kg{\kilogram} \newcommand\grain{\unit{grain}} \newcommand\ounce{\unit{oz}} % % Temperature \newcommand\kelvin{\unit{K}} \newcommand\K{\kelvin} \newcommand\celsius{\unit{{}^\circ C}} \newcommand\C{\celsius} \newcommand\fahrenheit{\unit{{}^\circ F}} \newcommand\F{\fahrenheit} % % Area \newcommand\sqft{\unit{sq\,\foot}} % square foot % % Volume \newcommand\liter{\unit{L}} \newcommand\gallon{\unit{gal}} % % Frequency \newcommand\hertz{\unit{Hz}} \newcommand\rpm{\unit{rpm}} % % Voltage \newcommand\volt{\unit{V}} \newcommand\V{\volt} \newcommand\millivolt{\milli\volt} \newcommand\mV{\milli\volt} \newcommand\kilovolt{\kilo\volt} \newcommand\kV{\kilo\volt} % % Current \newcommand\ampere{\unit{A}} \newcommand\A{\ampere} \newcommand\milliampereA{\milli\ampere} \newcommand\mA{\milli\ampere} \newcommand\kiloampereA{\kilo\ampere} \newcommand\kA{\kilo\ampere} % % Resistance \newcommand\ohm{\Omega} \newcommand\milliohm{\milli\ohm} \newcommand\kiloohm{\kilo\ohm} % correct SI spelling \newcommand\kilohm{\kilo\ohm} % "American" spelling used in siunitx \newcommand\megaohm{\mega\ohm} % correct SI spelling \newcommand\megohm{\mega\ohm} % "American" spelling used in siunitx % % Inductance \newcommand\henry{\unit{H}} \newcommand\H{\henry} \newcommand\millihenry{\milli\henry} \newcommand\mH{\milli\henry} % % Power \newcommand\watt{\unit{W}} \newcommand\W{\watt} \newcommand\milliwatt{\milli\watt} \newcommand\mW{\milli\watt} \newcommand\kilowatt{\kilo\watt} \newcommand\kW{\kilo\watt} % % Energy \newcommand\joule{\unit{J}} \newcommand\J{\joule} % % Composite units % % Torque \newcommand\ozin{\unit{\ounce}\,\unit{in}} \newcommand\newtonmeter{\unit{\newton\,\meter}} % % Pressure \newcommand\psf{\unit{psf}} % pounds per square foot \newcommand\pcf{\unit{pcf}} % pounds per cubic foot \newcommand\pascal{\unit{Pa}} \newcommand\Pa{\pascal} \newcommand\ksi{\unit{ksi}} % kilopound per square inch \newcommand\bar{\unit{bar}} \end{aligned}\end{align} \]

Mar 14, 2025 | 591 words | 6 min read

13.1.1. Task 1

Learning Objectives

• Encrypt a plaintext into ciphertext.

• Encode the ciphertext into an image at a specified bit offset.

Task Instructions

Save the flowcharts for each of your tasks in tp3_team_1_teamnumber.pdf. You will also need to include these flowcharts in your final report.

Step 1: Encryption Functions

Similarly to the Beaufort cipher, you implemented in Section 12.2.2, create functions that use the Rail Fence and Caesar cipher to encrypt a string. The functions should take two arguments: the plaintext message to be encrypted and the key. For the Caesar cipher, the key should be an integer representing the shift value. For the Rail Fence cipher, the key should be an integer representing the number of rails. These functions should return the encrypted ciphertext message. You can find details on the Rail Fence and Caesar ciphers in Section 12.1.1.

Note

Teams of 2 only need to implement the Beaufort cipher. Teams of 3 should implement the Beaufort cipher and one other cipher (either Rail Fence or Caesar). Teams of 4 or more should implement all three ciphers.

Step 2: Encoding Function

Update the encoding function you wrote in Section 12.2.3 to embed the binary message into an image, so that it can insert the binary message at a specified bit offset. For example, if the offset is 5, the function should start encoding the message after the 5th bit of the image.

Step 3: Main Function

Create a main function that collects the following inputs from the user:

• a choice of encryption method (Caesar, Rail Fence, or Beaufort)

• a plaintext message

• an encryption key

• the message start sequence

• the message end sequence

• the bit offset for encoding the message

• the path to an input image file (image without any encoding)

• the path to an output image file (where to save the encoded image)

• the path to a comparison image file (pre-encoded image for checking)

The function should encrypt the message using the chosen cipher, add the start and end sequences to the message, then convert the encrypted message to binary, and encode it into the image starting after the specified bit offset.

If the encoding is not successful, the main function should display an error message and stop. Otherwise, it should display a success message to the user and save and display the modified image.

Finally, building on the image comparison function you wrote in Section 12.2.1, the main function should compare the modified image with the comparison image, displaying the resulting image difference and printing whether the images are the same or different.

Use the files provided in the Table 13.2 to test your code.

Save your program as tp3_team_1_teamnumber.py.

Table 13.2 Image Files

Image File Name	Cipher	Key	Plaintext	Start Sequence	End Sequence	Bit Offset
ref_gry.png	None	None	None	None	None	None
ref_col.png	None	None	None	None	None	None
ref_gry_r.png	Rail Fence	3	East	12	21	13
ref_col_r.png	Rail Fence	6	ENGR 133!	44	77	3
ref_gry_b.png	Beaufort	Upa	Boiler	22	88	2
ref_col_b.png	Beaufort	is fun	Math 101	31	&&	15
ref_gry_c.png	Caesar	159	Red Rose	5	1	11
ref_col_c.png	Caesar	777	Love ENGR	40	04	9

Sample Output

Use the values in Table 13.3 below to test your program.

Table 13.3 Test Cases

Case	cipher choice	plaintext	cipher key	start_seq	end_seq	bit offset	input image path	output image path	compare image path
1	rail fence	East	3	12	21	13	ref_gry.png	gry_r.png	ref_gry_r.png
2	rail fence	ENGR 133!	6	44	77	3	ref_col.png	col_r.png	ref_col_r.png
3	beaufort	Boiler	Upa	22	88	2	ref_gry.png	gry_b.png	ref_gry_b.png
4	beaufort	Math 101	is fun	31	&&	15	ref_col.png	col_b.png	ref_col_b.png
5	caesar	Red Rose	159	5	1	11	ref_gry.png	gry_c.png	ref_gry_c.png
6	caesar	Love ENGR	777	40	04	9	ref_col.png	col_c.png	ref_col_c.png
7	caesar	Love ENGR	778	40	04	9	ref_col.png	col_c.png	ref_col_c.png
8	caesar	Love ENGR	777	40	04	25	ref_col.png	col_c.png	ref_col_c.png

Ensure your program’s output matches the provided samples exactly. This includes all characters, white space, and punctuation. In the samples, user input is highlighted like this for clarity, but your program should not highlight user input in this way.

Case 1 Sample Output

$ python3 tp3_team_1_teamnumber.py Enter the cipher you want to use for encryption: rail fence Enter the plaintext you want to encrypt: East Enter the key for the cipher: 3 Enter the start sequence: 12 Enter the end sequence: 21 Enter the bit offset before you want to start encoding: 13 Enter the path of the input image: ref_gry.png Enter the path for your encoded image: gry_r.png Enter the path of the image you want to compare: ref_gry_r.png Encrypted Message using Rail Fence Cipher: Exats Binary output message: 00110001 00110010 01000101 01111000 01100001 01110100 01110011 00110010 00110001 Message successfully encoded and saved to: gry_r.png The images are the same.

Fig. 13.1 Case_1_gry_r.png

Fig. 13.2 Case_1_plot_diff_image.png

Fig. 13.3 Case_1_plot_gry_r.png

Case 2 Sample Output

$ python3 tp3_team_1_teamnumber.py Enter the cipher you want to use for encryption: rail fence Enter the plaintext you want to encrypt: ENGR 133! Enter the key for the cipher: 6 Enter the start sequence: 44 Enter the end sequence: 77 Enter the bit offset before you want to start encoding: 3 Enter the path of the input image: ref_col.png Enter the path for your encoded image: col_r.png Enter the path of the image you want to compare: ref_col_r.png Encrypted Message using Rail Fence Cipher: ExNxG!R3 31 Binary output message: 00110100 00110100 01000101 01111000 01001110 01111000 01000111 00100001 01010010 00110011 00100000 00110011 00110001 00110111 00110111 Message successfully encoded and saved to: col_r.png The images are the same.

Fig. 13.4 Case_2_col_r.png

Fig. 13.5 Case_2_plot_col_r.png

Fig. 13.6 Case_2_plot_diff_image.png

Case 3 Sample Output

$ python3 tp3_team_1_teamnumber.py Enter the cipher you want to use for encryption: beaufort Enter the plaintext you want to encrypt: Boiler Enter the key for the cipher: Upa Enter the start sequence: 22 Enter the end sequence: 88 Enter the bit offset before you want to start encoding: 2 Enter the path of the input image: ref_gry.png Enter the path for your encoded image: gry_b.png Enter the path of the image you want to compare: ref_gry_b.png Encrypted Message using Beaufort Cipher: tb2jlt Binary output message: 00110010 00110010 01110100 01100010 00110010 01101010 01101100 01110100 00111000 00111000 Message successfully encoded and saved to: gry_b.png The images are the same.

Fig. 13.7 Case_3_gry_b.png

Fig. 13.8 Case_3_plot_diff_image.png

Fig. 13.9 Case_3_plot_gry_b.png

Case 4 Sample Output

$ python3 tp3_team_1_teamnumber.py Enter the cipher you want to use for encryption: beaufort Enter the plaintext you want to encrypt: Math 101 Enter the key for the cipher: is fun Enter the start sequence: 31 Enter the end sequence: && Enter the bit offset before you want to start encoding: 15 Enter the path of the input image: ref_col.png Enter the path for your encoded image: col_b.png Enter the path of the image you want to compare: ref_col_b.png Encrypted Message using Beaufort Cipher: 6sr8 ws1 Binary output message: 00110011 00110001 00110110 01110011 01110010 00111000 00100000 01110111 01110011 00110001 00100110 00100110 Message successfully encoded and saved to: col_b.png The images are the same.

Fig. 13.10 Case_4_col_b.png

Fig. 13.11 Case_4_plot_col_b.png

Fig. 13.12 Case_4_plot_diff_image.png

Case 5 Sample Output

$ python3 tp3_team_1_teamnumber.py Enter the cipher you want to use for encryption: caesar Enter the plaintext you want to encrypt: Red Rose Enter the key for the cipher: 159 Enter the start sequence: 5 Enter the end sequence: 1 Enter the bit offset before you want to start encoding: 11 Enter the path of the input image: ref_gry.png Enter the path for your encoded image: gry_c.png Enter the path of the image you want to compare: ref_gry_c.png Encrypted Message using Caesar Cipher: Uhg Urvh Binary output message: 00110101 01010101 01101000 01100111 00100000 01010101 01110010 01110110 01101000 00110001 Message successfully encoded and saved to: gry_c.png The images are the same.

Fig. 13.13 Case_5_gry_c.png

Fig. 13.14 Case_5_plot_diff_image.png

Fig. 13.15 Case_5_plot_gry_c.png

Case 6 Sample Output

$ python3 tp3_team_1_teamnumber.py Enter the cipher you want to use for encryption: caesar Enter the plaintext you want to encrypt: Love ENGR Enter the key for the cipher: 777 Enter the start sequence: 40 Enter the end sequence: 04 Enter the bit offset before you want to start encoding: 9 Enter the path of the input image: ref_col.png Enter the path for your encoded image: col_c.png Enter the path of the image you want to compare: ref_col_c.png Encrypted Message using Caesar Cipher: Ilsb BKDO Binary output message: 00110100 00110000 01001001 01101100 01110011 01100010 00100000 01000010 01001011 01000100 01001111 00110000 00110100 Message successfully encoded and saved to: col_c.png The images are the same.

Fig. 13.16 Case_6_col_c.png

Fig. 13.17 Case_6_plot_col_c.png

Fig. 13.18 Case_6_plot_diff_image.png

Case 7 Sample Output

$ python3 tp3_team_1_teamnumber.py Enter the cipher you want to use for encryption: caesar Enter the plaintext you want to encrypt: Love ENGR Enter the key for the cipher: 778 Enter the start sequence: 40 Enter the end sequence: 04 Enter the bit offset before you want to start encoding: 9 Enter the path of the input image: ref_col.png Enter the path for your encoded image: col_c.png Enter the path of the image you want to compare: ref_col_c.png Encrypted Message using Caesar Cipher: Jmtc CLEP Binary output message: 00110100 00110000 01001010 01101101 01110100 01100011 00100000 01000011 01001100 01000101 01010000 00110000 00110100 Message successfully encoded and saved to: col_c.png The images are different.

Fig. 13.19 Case_7_col_c.png

Fig. 13.20 Case_7_plot_col_c.png

Fig. 13.21 Case_7_plot_diff_image.png

Case 8 Sample Output

$ python3 tp3_team_1_teamnumber.py Enter the cipher you want to use for encryption: caesar Enter the plaintext you want to encrypt: Love ENGR Enter the key for the cipher: 777 Enter the start sequence: 40 Enter the end sequence: 04 Enter the bit offset before you want to start encoding: 25 Enter the path of the input image: ref_col.png Enter the path for your encoded image: col_c.png Enter the path of the image you want to compare: ref_col_c.png Given message is too long to be encoded in the image. Encrypted Message using Caesar Cipher: Ilsb BKDO Binary output message: 00110100 00110000 01001001 01101100 01110011 01100010 00100000 01000010 01001011 01000100 01001111 00110000 00110100

Table 13.4 Deliverables

Deliverables	Description
tp3_team_1_teamnumber.py	Your completed Python code.
tp3_team_1_teamnumber.pdf	Flowchart(s) for this task.