Types of Access Control:

I/O Management and Security

I/O Software Layers (User Level, Device Drivers, Kernel)

Types of Access Control

Threats andAttacks (Virus, Worms, Trojan, DoS)

Case Study: Modern Operating Systems

1. Discretionary Access Control (DAC)

Owner decides access permissions

Example:File owner gives read/write permission

2. Mandatory Access Control (MAC)

System enforces strict policies

Used in military or high-security systems

3. Role-Based Access Control (RBAC)

Access based on user roles

Example:Admin, Manager, Employee

4. Attribute-Based Access Control (ABAC)

Based on attributes (user, resource, environment)

Example:Access allowed only during office hours

Authentication vs Access Control

Feature	Authentication	Access Control
Purpose	Verify identity	Grant/deny permissions
Question Answered	Who are you?	What can you do?
Comes First?	Yes	After authentication
Example	Login with password	File read/write permissions

How They Work Together

User logs in → Authentication checks identity

System verifies → Access control applies permissions

User performs actions based on allowed rights

Short Summary (Exam Ready)

Authentication: Process of verifying user identity using passwords, biometrics, etc.

Access Control: Mechanism that determines user permissions to access resources.

Authentication happens first, followed by access control.

Cryptography Basics (Symmetric & Asymmetric Encryption)

Cryptography is the practice of securing information by converting it into an unreadable form so that only authorized parties can access it.

👉 Plain readable data = Plaintext
👉 Encrypted data = Ciphertext

 

 

1. Symmetric Encryption

Definition:
Uses a single key for both encryption and decryption.

Same key is shared between sender and receiver.

How it works:

Sender encrypts data using a secret key

Receiver uses the same key to decrypt it

Advantages:

Fast and efficient

Suitable for large data transfer

Disadvantages:

Key distribution problem (how to securely share the key?)

Less secure if the key is exposed

Examples:

AES

DES

2. Asymmetric Encryption

Definition:
Uses a pair of keys:

Public Key (shared openly)

Private Key (kept secret)

How it works:

Sender encrypts using receiver’s public key

Receiver decrypts using their private key

Advantages:

More secure (no need to share private key)

Enables digital signatures

Disadvantages:

Slower than symmetric encryption

Computationally expensive

📌 Examples:

RSA

ECC

Symmetric vs Asymmetric Encryption

Feature	Symmetric Encryption	Asymmetric Encryption
Keys Used	One shared key	Public + Private key pair
Speed	Fast	Slower
Security	Less secure (key sharing)	More secure
Use Case	Bulk data encryption	Key exchange, authentication

How They Are Used Together

In real systems (like HTTPS):

Asymmetric encryption is used to securely exchange a key

Symmetric encryption is then used for fast data transfer

Simple Analogy

Symmetric Encryption 🔑
Like a locker with one key—both people need the same key

Asymmetric Encryption 🔐
Like a mailbox—anyone can drop letters (public key), but only the owner can open it (private key)

 

 

 

Short Exam Note

Symmetric encryption uses a single key for encryption and decryption (fast but key sharing is risky).

Asymmetric encryption uses two keys (public & private), providing higher security but slower performance.

Both are often combined in real-world systems.