User authentication basics in Raspberry Pi - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is user authentication?

User authentication is the process of verifying who someone is before allowing access to a system or device.

beginner

Name two common methods of user authentication.

Two common methods are passwords and physical tokens (like a security key or fingerprint).

beginner

Why is it important to use strong passwords?

Strong passwords help protect your device from unauthorized access by making it hard for others to guess or crack your password.

intermediate

What is two-factor authentication (2FA)?

2FA adds an extra step to login by requiring two types of proof, like a password plus a code sent to your phone.

beginner

How does a Raspberry Pi check a user's identity during login?

It asks for a username and password, then compares the password to the stored one to decide if access is allowed.

What does user authentication verify?

A The user's device brand

B The user's internet speed

C Who the user is

D The user's location

User authentication checks the identity of the user trying to access the system.

Which of these is NOT a common authentication method?

A Screen brightness

B Password

C Fingerprint

D Security token

Screen brightness is unrelated to verifying user identity.

Why use two-factor authentication?

A To make login faster

B To add extra security

C To avoid passwords

D To share passwords

Two-factor authentication adds an extra security step beyond just a password.

What should a strong password include?

A Only letters

B Simple words

C Your name

D A mix of letters, numbers, and symbols

Strong passwords use a mix of characters to be harder to guess.

On a Raspberry Pi, what happens after entering your password?

A The system checks if it matches the stored password

B The system restarts

C The system updates automatically

D The system deletes files

The Raspberry Pi compares the entered password to the saved one to allow access.

Explain in your own words what user authentication is and why it matters on devices like the Raspberry Pi.

Think about how you prove who you are before using a device.

Describe two ways to make user authentication more secure.

Consider extra steps beyond just a password.

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