Computer Science
Grade 9
20 min
Authentication
Authentication
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1
Introduction & Learning Objectives
Learning Objectives
Define authentication and differentiate it from authorization.
Explain the roles of the client and server in the authentication process.
Describe the purpose of hashing passwords for security.
Diagram the step-by-step flow of a user registration (sign-up) process.
Diagram the step-by-step flow of a user login process.
Identify the key data (credentials) needed for authentication.
Ever wonder how your favorite game or social media app knows it's you and not someone else? 🤔 Let's unlock the secrets of digital identity!
This lesson explores authentication, the process of verifying who a user is. We'll learn how websites and apps use a 'digital bouncer' to check your ID before letting you in, which is a fundamental concept for keepi...
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Key Concepts & Vocabulary
TermDefinitionExample
AuthenticationThe process of proving you are who you say you are. It's like showing your ID card to a security guard.Entering your username and password on a website to log in.
AuthorizationThe process of determining what an authenticated user is allowed to do. It's what rooms your ID card gives you access to after you're inside the building.A regular user can post photos, but an administrator can delete any user's photo.
CredentialsThe pieces of information used to verify your identity, most commonly a username and password.Your email 'student@school.com' and your password 'MySecretP@ssword1'.
Client-SideThe part of an application that runs on the user's device, like a web browser or a mobile app. It's what you see a...
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Core Syntax & Patterns
The Registration Pattern
Client sends new credentials -> Server validates data -> Server hashes password -> Server stores new user record in database.
This is the standard flow for creating a new user account. The most critical steps are validating the data (e.g., is the email already in use?) and hashing the password before saving it.
The Login Pattern
Client sends credentials -> Server finds user by username -> Server hashes submitted password -> Server compares new hash with stored hash -> If they match, grant access.
This is the standard flow for verifying an existing user. The server never un-hashes the stored password; it always hashes the incoming password and compares the results.
The 'Never Trust the Client' Rule
All critical val...
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Challenging
A developer implements a client-side check to see if a username is available as the user types. This gives instant feedback. Why must the server *still* perform its own check for an existing username when the registration form is submitted?
A.Because the client-side check might be slow.
B.Because the server's database is the only place that can hash the username.
C.Because two users could submit the same new username at almost the exact same time.
D.Because a malicious user can bypass the client-side check and submit the form directly to the server.
Challenging
Considering both the 'Registration Pattern' and the 'Login Pattern', what is the one critical operation involving the user's password that is performed on the server-side in BOTH processes?
A.Storing the password in the database.
B.Hashing the password submitted by the client.
C.Comparing two different passwords.
D.Sending the password back to the client for confirmation.
Challenging
If hashing is a 'one-way process' and the server never stores the original password, how does the server verify a correct password during login?
A.The server makes a temporary, best-guess reversal of the stored hash.
B.The server asks the client to send the hashed version of the password for a direct comparison.
C.The server applies the same one-way hash function to the submitted password and compares the result to the stored hash.
D.The server trusts the client's claim that the password is correct after the first successful login.
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