MTRX1702 Mechatronics 1
Assignment 3
Steganography
MTRX1702 Mechatronics 1
Concealing and extracting data hidden from images.
Overview
MTRX1702 Mechatronics 1
● One Program
○ steg ●
Three Calling Variants
○ Encoding:
■ source_image input_data output_image
○ Decoding:
■ source_image output_data
■ source_image ●
Extra arguments that control output
○ -v verify data integrity
○ -c print checksum
○ -p print encoded data
○ -n print length of data
○ -h help message
Assignment Structure
MTRX1702 Mechatronics 1
Data is hidden in the least significant bits of the pixel data.
Hiding Data
MTRX1702 Mechatronics 1
Data Format
Component Bits Stored Bytes in File
File Header h N/A m
Length of stored data n 32 32
Stored Data d n * 8 p
Unmodified Data u N/A q
Checksum c 32 32
MTRX1702 Mechatronics 1
● An extension to conceal within png files is worth a bonus
10%.●
It is much more challenging.●
It tests your ability to read documentation and link to external
libraries.●
The format involves editing pixel values, but direct copy of
metadata is not necessarily possible. We will compare by checking pixel values (test cases pending).
● Help will not be given by staff/tutors. It is bonus marks and
not required for 100%.
Extension and Bonus Marks
MTRX1702 Mechatronics 1
● Start working on the assignment early
○ Create your Makefile - either by hand or from template
○ You still have 4 quizzes to complete by the same time.●
Use the terminal
○ GDB can be used to validate code, debug errors●
Edstem can view bitmaps
○ Bitmaps pixel data starts at bottom left working across the screen row by row finishing top right
○ Higher bits per pixel show up as “random” noise.●
Download images/inspect pixel values
○ Create test images by hand in image editor●
Test by hand as you cannot see all test cases
○ Baboon.bmp is supplied as a blank image to test with.
How to do Well
MTRX1702 Mechatronics 1
● 75% on test cases
● 25% on code quality:
○ Documentation/self documenting/comments
○ Indentation/spacing/formatting
○ Functions/module design
○ Overall quality and clarity
● 10% bonus extension
○ Handle PNG images.
Marking Breakdown
User Input Checks Encode/Decode
30 45
MTRX1702 Mechatronics 1
This is an individual assignment
The work should be your own:
● No code from elsewhere, open source or otherwise
○ Can call standard library functions
○ Can call getopt for argument parsing.
○ Can use libpng for the extension.●
Algorithms/program structure must reflect only your thought
process.●
You can consult others about use of library functions
○ e.g. fread, fopen, fwrite
We are assessing not just knowledge of C but your ability to design, implement and test solutions to a given problem.
Academic Honesty
MTRX1702 Mechatronics 1
● Plagiarism means “presenting another person’s work as one’s own work by
presenting, copying or reproducing it without appropriate acknowledgement of the
source”.
● This includes:
○ Copying without proper referencing. Direct quotes from any source must be in
quotation marks “like this”.
○ Treating an individual assignment as though it were a group assignment.
If unsure, check with your lecturer how much cooperation is allowed.
● Academic dishonesty includes:
○ Recycling – (self plagiarism) that is, the resubmission for assessment of work
that is the same, or substantially the same, as work previously submitted for
assessment in the same or in a different unit of study
○ Sharing your work – if you knowingly allow another student to see your
assignment (draft or complete) you are “seeking to obtain or obtaining
academic advantage for oneself or for others”
○ Other acts such as engaging another person to contribute to an assignment
(either for money or free), communicating during an exam, bringing forbidden
materials to an exam, etc…
Academic Honesty
MTRX1702 Mechatronics 1
● Plagiarism and academic dishonesty are not acceptable at this University.
Depending on severity, penalties include:
○ Mark of zero for an assessment,
○ Grade of 0 FA for unit of study,
○ Referral to the University Registrar to consider exclusion
from further study at the University of Sydney.
● Links:
○ General information page for Academic Integrity:
http://sydney.edu.au/students/academic-dishonesty-and-plagiarism.html
○ More details on Academic Honesty:
http://sydney.edu.au/students/academic-integrity.html
○ The complete University of Sydney policy:
http://sydney.edu.au/policies/showdoc.aspx?recnum=PDOC2012/254RendNu
m=0
Academic Honesty