User authentication basics in Raspberry Pi - Mini Project: Build & Apply

User authentication basics

📖 Scenario: You are building a simple user login system for a Raspberry Pi project. The system will check if a username and password match stored data to allow access.

🎯 Goal: Create a program that stores user credentials, sets a username and password to check, verifies if the credentials match, and prints a message showing if login is successful or not.

📋 What You'll Learn

Create a dictionary with usernames as keys and passwords as values

Create variables for input username and password to check

Use an if statement to verify if the username exists and the password matches

Print 'Login successful' if credentials match, otherwise print 'Login failed'

💡 Why This Matters

🌍 Real World

User authentication is essential for controlling access to devices like Raspberry Pi projects, home automation, or personal servers.

💼 Career

Understanding basic authentication helps in roles like system administration, IoT development, and software engineering where security is important.

1

Create user credentials dictionary

Create a dictionary called users with these exact entries: 'alice': 'wonderland', 'bob': 'builder', 'carol': 'sunshine'

Raspberry Pi

# Create the users dictionary with usernames and passwords
# Your code here

Hint

Use curly braces {} to create a dictionary with keys and values separated by colons.

2

Set username and password to check

Create two variables called username and password and set them to 'bob' and 'builder' respectively

Raspberry Pi

users = {'alice': 'wonderland', 'bob': 'builder', 'carol': 'sunshine'}
# Set username and password variables
# Your code here

Hint

Assign the exact strings to the variables using the equals sign.

3

Check if username and password match

Write an if statement that checks if username is a key in users and if users[username] equals password

Raspberry Pi

users = {'alice': 'wonderland', 'bob': 'builder', 'carol': 'sunshine'}
username = 'bob'
password = 'builder'
# Check credentials with if statement
# Your code here

Hint

Use in to check if the username exists and compare the stored password with the input password.

4

Print login result

Write a print statement that prints 'Login successful' if login_success is True, otherwise prints 'Login failed'

Raspberry Pi

users = {'alice': 'wonderland', 'bob': 'builder', 'carol': 'sunshine'}
username = 'bob'
password = 'builder'
if username in users and users[username] == password:
    login_success = True
else:
    login_success = False
# Print login result
# Your code here

Hint

Use an if statement to print the correct message based on the login_success variable.

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