If you haven't already, run pip install cryptography and pip install fire, two libraries we'll be using during this course.
For homework you'll make generate_key(), encrypt(message), and decrypt(key, ciphertext) work
by using other functions in the file.
Contact me immediately if you have errors or difficulty getting past this stage.
Go down to PyCharm's Terminal tab and type these commands there. You'll be using it for the rest of the homework.
Run the command python main.py base64_encode "hello from kris" and see what
it does.
The program should print: b'aGVsbG8gZnJvbSBrcmlz' (remember that the b
means this is a string of bytes)
Run the command python main.py base64_decode "QmFzZTY0IGVuY29kaW5nIGlzIE5PVCBlbmNyeXB0aW9uLg==" and see what it
does.
It should decode to the string b'Base64 encoding is NOT encryption.'
This function converts your message to bytes and also adds padding, which is required for a block-cipher if your message isn't long enough.
Run python main.py message_to_bytes "hello world" and you should get the
output:
Unpadded message: hello world
Padded data: b'hello world\x05\x05\x05\x05\x05'
b'hello world\x05\x05\x05\x05\x05Run python main.py remove_pkcs7_padding "hello world\x05\x05\x05\x05\x05"
You should get the output:
Removing padding: hello world\x05\x05\x05\x05\x05
padded_data as bytes: b'hello world\\x05\\x05\\x05\\x05\\x05'
Removing PKCS7 padding for: b'hello world\x05\x05\x05\x05\x05'
Data without padding: b'hello world'
b'hello world'Now that you know how those 4 functions work, run the command: python main.py generate_key. You should get the output: Your 128-bit key as bytes is: b' ..some random data as bytes... once it's working.
Run the command python main.py encrypt "testing encryption".
Once you've made it work you should get output similar (but different because of the random key) to the following:
Plaintext message to encrypt is: testing encryption
Generating a key:
Your 128-bit key as bytes is: b'\x8c\xb1\xa2\xbdYw\x12\x10B\xa8\xa0[AJ\x96X'
Key: b'\x8c\xb1\xa2\xbdYw\x12\x10B\xa8\xa0[AJ\x96X'
Base64 encoded key: b'jLGivVl3EhBCqKBbQUqWWA=='
Unpadded message: testing encryption
Padded message: b'testing encryption\x0e\x0e\x0e\x0e\x0e\x0e\x0e\x0e\x0e\x0e\x0e\x0e\x0e\x0e'
Ciphertext: b'7\x0f\xf5\xc0\xc6L\xdd\x02\x1f]\xd2\xce\xcbl\xe1\xf6\xe5p\x07J\x9b\x9arf\x82RI\xd7\x8e+\x1b\xed'
Base64 encoded ciphertext: b'Nw/1wMZM3QIfXdLOy2zh9uVwB0qbmnJmglJJ144rG+0='Save the key and ciphertext somewhere (REMOVE the b at the start).
If your ciphertext was b'somethingbase64 then make sure you remove the b
at the start. Run the command python main.py decrypt KEY CIPHERTEXT but
replace KEY and CIPHERTEXT with your key and ciphertext from 6.
If your decrypt function works, congratulations you've now built a program that uses modern encryption (although it still has a lot of ways to be attacked!).
Decrypt the following message and send me your solution.
- Now that your
encryptanddecryptfunctions work as expected, decrypt the following text.
Using the key OrTH5lv6THAc4fqmMrA2TQ==, decrypt the following ciphertext
(triple-click to select the text):
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After decrypting 8), encrypt the message "Hello from Firstname-IDNumber. The answer is: {ANSWER}." (replace Firstname and IDNumber with your first name and student ID number, and ANSWER with the answer from 8).
- Save the
keyandciphertextand send them to me with the title 'Week 4 Homework Solution'.