Authentication and Verification

This lesson covers authentication and verification as required by OCR J277 Section 2.4. Authentication confirms the identity of a user, while verification confirms that data has been entered or transmitted correctly. Both are essential aspects of producing robust programs.

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What Is Authentication?

Authentication is the process of confirming that a user is who they claim to be. It is used to control access to systems, data, and features. Without authentication, anyone could access sensitive information or perform restricted actions.

Common Authentication Methods

Method	Description	Example
Username and password	User provides a unique identifier and secret password	Logging into a school network
Two-factor authentication (2FA)	User provides two forms of identification	Password + code sent to phone
Biometric	Uses unique physical characteristics	Fingerprint, face recognition, iris scan
Security questions	User answers pre-set personal questions	"What is your mother's maiden name?"

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Implementing Password Authentication

OCR Pseudocode:

storedUsername = "admin"
storedPassword = "Secure#123"
maxAttempts = 3
attempts = 0
authenticated = false

while attempts < maxAttempts AND authenticated == false
    username = input("Enter username: ")
    password = input("Enter password: ")

    if username == storedUsername AND password == storedPassword then
        authenticated = true
        print("Login successful!")
    else
        attempts = attempts + 1
        remaining = maxAttempts - attempts
        print("Incorrect. " + str(remaining) + " attempts remaining.")
    endif
endwhile

if authenticated == false then
    print("Account locked. Too many failed attempts.")
endif

Python:

stored_username = "admin"
stored_password = "Secure#123"
max_attempts = 3
attempts = 0
authenticated = False

while attempts < max_attempts and not authenticated:
    username = input("Enter username: ")
    password = input("Enter password: ")

    if username == stored_username and password == stored_password:
        authenticated = True
        print("Login successful!")
    else:
        attempts += 1
        remaining = max_attempts - attempts
        print(f"Incorrect. {remaining} attempts remaining.")

if not authenticated:
    print("Account locked. Too many failed attempts.")

OCR Exam Tip: When writing authentication code in the exam, always include: (1) a limited number of attempts, (2) appropriate error messages, and (3) a lockout mechanism after too many failures. These features demonstrate defensive design.

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Strong Passwords

A robust authentication system requires strong passwords. Good password policies include:

Requirement	Purpose
Minimum length (e.g. 8+ characters)	Longer passwords are harder to crack
Mix of upper and lower case	Increases the number of possible combinations
Include numbers	Further increases complexity
Include special characters (!@#$%)	Maximum complexity
Not a common word or pattern	Prevents dictionary attacks

Password Strength Checker

OCR Pseudocode:

function checkPasswordStrength(password)
    score = 0

    if password.length >= 8 then
        score = score + 1
    endif

    hasUpper = false
    hasLower = false
    hasDigit = false
    hasSpecial = false