2. What is iOS and its Structure

1. Introduction to Jailbreaking and Tools

A. What is iOS ?

Reference - https://en.wikipedia.org/wiki/IOS

• iOS is a mobile operating system created and developed by Apple Inc. exclusively for iPhone, iPod,iPad & Apple TV
• Provides multi-tasking (allowing a user to perform more than one computer task)
• It only allows to run Apple signed applications.

B. What is Jailbreaking ?

• Jailbreak gives full access to the device
• We Can say it is the privilege escalation from a normal user to root.
• Allows to install Apps which are not authorized
• Install Application from Cydia which is AppStore for jailbreak Devices.

Types of jailbreak

Tethered

• Users need to reconnect to their computer every time the device is restarted 

Untethered

• its one-time activity. no need to reconnect. 

We will see how to jailbreak in an upcoming blog post.
                           


D. iOS Architecture

• It contains an intermediate layer between the applications and the hardware so they do not communicate directly.
• it contains four layers

•  Core OS
•  Core Services
•  Media Services
•  Cocoa Touch

Let us discuss one by one

1. Core OS Layer

• A layer in which most applications interact with.
• All the iOS technologies are built on the low-level features provided by the Core OS layer.
• These technologies include Core Bluetooth Framework, External Accessory Framework,     Accelerate Framework, Security Services Framework, Local Authorisation Framework, etc.
• The developer has limited access to this layer. still, the developer has the privileges to access the following frameworks

• Accelerate - Big number and DSP calculations
• External Accessory - Communicate with hardware accessories.
• Security - Certificates and Cryptography
• System - Low-level Operating system method

2. Core Services

• The Core Services layer provides an abstraction over the services provided in the Core OS layer.
• It provides fundamental access to iPhone OS services. 
• Following frameworks available in the cure services layer.

• Cloudkit Framework - The data can be moved between the app the iCloud using the Cloudkit Framework.

• Core Foundation Framework - This provides data management and service features for iOS apps.

• Core Data Framework - The data model of the model view controller app is handled using the Core Data Framework.

• Address Book Framework - The address book framework provides access to the contacts database of the user.

• Core Motion Framework - All the motion-based data on the device is accessed using the core motion framework.

• Healthkit Framework - The health-related information of the user can be handled by this new framework.

• Core Location Framework - This framework provides the location and heading information to the various apps.

• Core Location-  GPS, cellular or wi-fi based location services

3. Media Services

•  The Media layer provides multimedia services that you can use within your iPhone.
•  The media layer enables all the graphics, audio and video technology of the system. 
•  Allows the developer to work with photos, videos, audios, animations, graphics like things.
•  It contains the following frameworks.

• AVFoundation- Advanced audio and video 
• UIKit Graphics- Designing images and animating the view content.
• Core Graphics Framework- Support 2-D vector and image-based rendering and is the Native drawing engine for iOS apps.
• Core Animation- The Core Animation technology optimizes the animation experience of the apps.
• Core Audio-Low-level audio
• Media Player-Support audio, video playback & enables the user to use their iTunes library.
• Core Text-Advanced text layouts and fonts

4. Cocoa Touch Layer

• Cocoa-Touch layer provides an abstraction layer to expose the various libraries for programming the iPhone, and other IOS devices.
•  As per Apple documentation following frameworks are there 

• UIKit- UI element, life cycle management, etc
• Message Kit- Responsible for Email, SMS 
• Address Book- Contact, editing.
• Event Kit- Alarm, Calendar events, etc.
• Game Kit- Responsible for gaming activity.
• iAd- It supports Apple’s advertisement platform 
• Map Kit- Google map, Apple map.
• Message Kit- Responsible for Email etc  
• 
  

Reference - https://developer.apple.com/documentation/