User authentication basics in Raspberry Pi - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the entered password matches the stored password.

Raspberry Pi

if entered_password [1] stored_password:
    print("Access granted")
else:
    print("Access denied")

Drag options to blanks, or click blank then click option'

A<

B!=

C==

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using assignment operator '=' instead of comparison '=='.

We use == to compare if two passwords are the same.

2fill in blank

medium

Complete the code to ask the user for their username.

Raspberry Pi

username = input([1])

Drag options to blanks, or click blank then click option'

A"Enter your username: "

B'Enter your email: '

C'Enter your password: '

D"Enter your PIN: "

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong prompt message that asks for password or PIN.

The prompt should ask for the username, so the message is "Enter your username: ".

3fill in blank

hard

Fix the error in the code to securely check the password using hashing.

Raspberry Pi

import hashlib

hashed_input = hashlib.sha256(entered_password.encode()).hexdigest()
if hashed_input [1] stored_hashed_password:
    print("Access granted")
else:
    print("Access denied")

Drag options to blanks, or click blank then click option'

A=

B==

Cis

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' which assigns instead of compares.

Using 'is' which checks identity, not equality.

To compare hashed passwords, use == to check equality.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that stores usernames and their hashed passwords only if the password length is greater than 5.

Raspberry Pi

user_hashes = {user: hashlib.sha256([1].encode()).hexdigest() for user, [2] in users.items() if len(password) > 5}

Drag options to blanks, or click blank then click option'

Apassword

Bpassw

Cpwd

Dpasswd

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names that are not defined in the loop.

Both blanks refer to the password variable, which is named 'password' in the loop.

5fill in blank

hard

Fill all three blanks to create a function that checks if a username exists and the password matches the stored hash.

Raspberry Pi

def authenticate([1], [2]):
    if [1] in user_db and hashlib.sha256([2].encode()).hexdigest() == user_db[[1]]:
        return True
    return False

Drag options to blanks, or click blank then click option'

Ausername

Bpassword

Duser

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing variable names or using undefined variables.

The function takes username and password as parameters. The username is checked in the database and used to get the stored hash.

Practice

1. What is the main purpose of user authentication on a Raspberry Pi?

easy

A. To speed up the Raspberry Pi's processing power

B. To verify the identity of a user before allowing access

C. To install new software automatically

D. To connect to the internet faster

Solution

1. Step 1: Understand user authentication

   User authentication is about checking who you are before access is granted.

2. Step 2: Identify the correct purpose

   Only To verify the identity of a user before allowing access describes verifying identity before access, which matches authentication.

3. Final Answer:

   To verify the identity of a user before allowing access -> Option B

4. Quick Check:

   User authentication = verify identity [OK]

Hint: Authentication means checking who you are [OK]

Common Mistakes:

• Confusing authentication with performance or internet speed
• Thinking authentication installs software
• Mixing authentication with network connection

2. Which of the following is the correct way to check a username and password in Python on Raspberry Pi?

easy

A. if username = 'pi' and password = 'raspberry':

B. if username = 'pi' or password = 'raspberry':

C. if username == 'pi' and password == 'raspberry':

D. if username == 'pi' or password == 'raspberry':

Solution

1. Step 1: Identify correct comparison operator

   In Python, '==' checks equality; '=' assigns values.

2. Step 2: Check logical operators for authentication

   Both username and password must match, so use 'and' not 'or'.

3. Final Answer:

   if username == 'pi' and password == 'raspberry': -> Option C

4. Quick Check:

   Use '==' and 'and' for correct check [OK]

Hint: Use '==' to compare and 'and' to require both true [OK]

Common Mistakes:

• Using '=' instead of '==' for comparison
• Using 'or' instead of 'and' to check both credentials
• Mixing assignment and comparison operators

3. What will be the output of this Python code on Raspberry Pi?

username = 'pi'
password = 'raspberry'
input_user = 'pi'
input_pass = 'wrongpass'

if input_user == username and input_pass == password:
    print('Access granted')
else:
    print('Access denied')

medium

A. Access granted

B. SyntaxError

C. No output

D. Access denied

Solution

1. Step 1: Compare input username and password

   input_user matches username 'pi', but input_pass is 'wrongpass', not 'raspberry'.

2. Step 2: Evaluate the if condition

   Since password check fails, condition is false, so else block runs.

3. Final Answer:

   Access denied -> Option D

4. Quick Check:

   Password mismatch means access denied [OK]

Hint: Both username and password must match exactly [OK]

Common Mistakes:

• Assuming partial match grants access
• Confusing syntax error with logic error
• Ignoring else block output

4. Find the error in this Raspberry Pi Python authentication code:

username = 'pi'
password = 'raspberry'
input_user = input('Enter username: ')
input_pass = input('Enter password: ')

if input_user = username and input_pass = password:
    print('Access granted')
else:
    print('Access denied')

medium

A. Using '=' instead of '==' in if condition

B. Missing colon ':' after if statement

C. input() function is used incorrectly

D. Print statements are missing parentheses

Solution

1. Step 1: Check the if condition syntax

   The code uses '=' which assigns values, but '==' is needed to compare values.

2. Step 2: Verify other syntax parts

   Colons are present, input() usage is correct, and print() has parentheses.

3. Final Answer:

   Using '=' instead of '==' in if condition -> Option A

4. Quick Check:

   Use '==' to compare, not '=' [OK]

Hint: Use '==' for comparison, '=' is assignment [OK]

Common Mistakes:

• Confusing assignment '=' with comparison '=='
• Forgetting colon after if statement
• Misusing input() or print() syntax

5. You want to improve a Raspberry Pi login program to lock the user out after 3 failed attempts. Which approach is best?

hard

A. Use a counter variable to track failed attempts and stop after 3

B. Change the password automatically after 3 tries

C. Print 'Access granted' even if password is wrong 3 times

D. Restart the Raspberry Pi after each failed attempt

Solution

1. Step 1: Understand the goal of locking out after 3 failures

   We need to count failed tries and stop allowing login after 3.

2. Step 2: Evaluate options for implementing this

   Using a counter variable to track attempts is the correct and simple method.

3. Final Answer:

   Use a counter variable to track failed attempts and stop after 3 -> Option A

4. Quick Check:

   Counting attempts controls login lockout [OK]

Hint: Count failed tries with a variable to limit attempts [OK]

Common Mistakes:

• Changing password automatically without user consent
• Allowing access despite wrong passwords
• Restarting device unnecessarily on failure