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.

flowchart TD
    A[Start login] --> B[attempts = 0]
    B --> C{attempts < MAX_ATTEMPTS?}
    C -- No --> L[Lock account / Access denied]
    C -- Yes --> D[Read username + password]
    D --> E{Match stored credentials?}
    E -- Yes --> F[authenticated = true]
    F --> G[Grant access]
    E -- No --> H[attempts = attempts + 1]
    H --> I[Show 'Incorrect — N attempts left']
    I --> C

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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

    for i = 0 to password.length - 1
        char = password.substring(i, i + 1)
        asciiVal = ASC(char)
        if asciiVal >= 65 AND asciiVal <= 90 then
            hasUpper = true
        elseif asciiVal >= 97 AND asciiVal <= 122 then
            hasLower = true
        elseif asciiVal >= 48 AND asciiVal <= 57 then
            hasDigit = true
        else
            hasSpecial = true
        endif
    next i

    if hasUpper then score = score + 1 endif
    if hasLower then score = score + 1 endif
    if hasDigit then score = score + 1 endif
    if hasSpecial then score = score + 1 endif

    return score
endfunction

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What Is Verification?

Verification is the process of checking that data has been entered or transmitted correctly. Unlike validation (which checks if data is reasonable), verification checks that data is accurate — that it matches what was intended.

Two Types of Verification

Type	Description	How It Works
Double entry	User enters the data twice	Compare both entries — if they match, the data is likely correct
Screen/visual check	User reviews data on screen before confirming	Displays entered data and asks "Is this correct? (Y/N)"

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Double Entry Verification

OCR Pseudocode:

do
    email1 = input("Enter your email: ")
    email2 = input("Confirm your email: ")
    if email1 != email2 then
        print("Error: emails do not match. Please try again.")
    endif
until email1 == email2
print("Email confirmed: " + email1)

Python:

while True:
    email1 = input("Enter your email: ")
    email2 = input("Confirm your email: ")
    if email1 == email2:
        break
    print("Error: emails do not match. Please try again.")
print("Email confirmed:", email1)

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Screen/Visual Verification

OCR Pseudocode:

name = input("Enter your name: ")
email = input("Enter your email: ")
phone = input("Enter your phone number: ")

print("Please confirm your details:")
print("Name: " + name)
print("Email: " + email)
print("Phone: " + phone)

confirm = input("Is this correct? (yes/no): ")
if confirm.lower == "yes" then
    print("Details saved.")
else
    print("Please re-enter your details.")
endif

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Validation vs Verification

This is a very commonly tested distinction in the OCR exam:

Feature	Validation	Verification
Purpose	Checks data is reasonable/acceptable	Checks data is accurate/correct
What it checks	Format, range, type, length, presence	That data matches what was intended
Example	Age must be 0–150	User enters email twice to confirm
Can be automated?	Yes — rules can be coded	Partially — double entry is automated; visual check requires human
Done by	The computer	The computer and/or the user

OCR Exam Tip: If asked "What is the difference between validation and verification?", the key answer is: validation checks that data is reasonable and meets certain rules, while verification checks that data has been entered correctly and is accurate. A range check is validation; entering your email twice is verification.

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Summary