Applied Cryptography Assignment # 1 Task 0: [2 marks] a) run birthday_attack_statistics.py and copy the last line of the console output into the assignment_answers.txt file for subtask a. The console line should start with "average number of attempts ...." b) now, modify birthday_attack_statistics.py to start a search from your birthday date up until the assignment due date (24 September 2023). Use the lecture slides on the birthday paradox to calculate what your expected size should be for a 50% chance of a collision to have occured with this new date range. Run your updated birthday_attack_statistics.py and copy the new updated console output (just the last line) for subtask b. In the line underneath, indicate if the average was close (within +-2 of what you calculated) or not close (outside the +-2 of what you calcualted). example for b below: average number of attempts to find a collision over the 1000 runs is 5.532 not close Task 1: [4 marks] You have been be given an encrypted file that a student has encrypted, but they forgot which student ID they typed. You suspect they might have used the student ID 4000000 instead of their student number. ?modify the task_1(...) function in crypto_a1_activity.py ?modify the decrypt_file(...) function in crypto_a1_activity.py to call the functions you need to try and decrypt a file. We've provided some empty functionsin the file for you to complete with some guidance. You will also need to implmenet the decrypt_file(...) function for your task 1 to be completed. Once you've completed the code, run your python code to decrypt the file and see what the output was: (how to run it...) Windows users in vscode terminal: python crypto_a1_activity.py 40000000 task1 windows_data_encrypted.txt windows_data_decrypted.txt Mac / Linux users in vscode: python crypto_a1_activity.py 40000000 task1 mac_linux_data_encrypted.txt mac_linux_data_decrypted.txt If you've succesfully decrypted the file, then copy line 5 of the text file and paste it as your answer. Hopefully the text should be readable in English... Task 2: [3 marks] Now that you've sucessfully decrypted the file, what we would like to you to do is re-encrypt the file. You will need to add code into the task_2 function and also implement the encrypt_file function ?modify the task_2(...) function in crypto_a1_activity.py ?modify the encrypt_file(...) function in crypto_a1_activity.py If you've successfully implemented the function, then you should be able to run the python file with student number 40000000, take in your decrypted file, and then output to a newly encrypted txt. You will notice that the file is not the same as the original encrypted file that we provided you. That is because the fernet encrypt function actually does some cheeky things under the hood with the choice of cypher block mode (see week 5 lectures)! Use the fernet library link here [ https://cryptography.io/en/latest/fernet/ ] to find out what block mode fernet uses for encryption and tell us what block mode it uses in your answer for task 2. python crypto_a1_activity.py 40000000 task2 windows_data_decrypted.txt windows_data_decrypted_encrypted.txt or python crypto_a1_activity.py 40000000 task2 mac_linux_data_decrypted.txt mac_linux_data_decrypted_encrypted.txt 2) Take the same decrypted file and encrypt it using your own student number. save the output file as task2.txt python crypto_a1_activity.py YOUR SID HERE... task2 windows_data_decrypted.txt task2.txt python crypto_a1_activity.py YOUR SID HERE... task2 mac_linux_data_decrypted.txt task2.txt check the start of your has with our version run with your student number. [assignment 2 - task 2 modification]: upload the task2.txt as one of the files you submit. We will then check that it is able to be decrypted using our decryption algorithm.[note: If you've been able to decrypt the file from task 1, and are able to decrypt your task2 file, then you should be ok] Task 3: [2 mark] use your student number to encrypt and decrypt the decrypted file. Write "Success:" or "not success" in your answer file for task 3. provide the first 20 characters of the encrypted file (which should be the same as task 2). [assignment 2 - task 3 clarification]: we will check your task2 file and run some checks on it, we will aslo you YOUR decryption function to decrypt your task 2 file. ?modify the task_3(...) function in crypto_a1_activity.py Task 4: [2 marks] hash the unencrypted data file using SHA256 and copy the hash into task 4 python crypto_a1_activity.py YOUR SID HERE... task4 windows_data_decrypted.txt task4.txt or python crypto_a1_activity.py YOUR SID HERE... task4 mac_linux_data_decrypted.txt task4.txt [assignment 2 - task 2 modification]: upload task4.txt with your assignment submission ?modify the task_4(...) function in crypto_a1_activity.py ?modify the generate_hash(...) function in crypto_a1_activity.py Task 5: [2 marks] hash the file that was encrypted with your student number (task2.txt) and save the resultsin task5.txt copy the hash stored in the output file into the assignment_answers.txt file in task 5.

Attachments:

Applied-Crypt....zip