What is the Keychain

The keychain is the best place to store small secrets, like passwords and cryptographic keys. You use the functions of the keychain services API to add, retrieve, delete, or modify keychain items.

Apple Inc. uses keychains as a password management system in Mac OS and iOS.  Apple recommends storing only a small amount of data in the Keychain. If you need to secure something big you can encrypt it manually, save to a file and store the key in the Keychain.

Basic Keychain Concepts

• Keychain: The keychain is a secure and encrypted storage place for sensitive data. You can think of it is a database of sensitive information.
• Keychain Item: This is a registry in the keychain.
• Item Class: You can think of a class as a template of information you want to store. The keychain offers classes for different common credentials, such as username/password pairs, a certificate, a generic password, and more.   

Implementation of Keychain for storing,retrieving and deleting data 

You can use Swift Package Manager to install SwiftKeychainWrapper using Xcode:

1. Open your project in Xcode
2. Click "File" -> "Swift Packages" -> "Add Package Dependency". 
3. Paste the following URL: https://github.com/jrendel/SwiftKeychainWrapper
4. Click "Next" -> "Next" -> "Finish"  

OR

Install SwiftKeychainWrapper via podfile by adding pod 'SwiftKeychainWrapper' to your pod file.

SwiftKeychainWrapper

It provides a singleton instance that is set up to work for most needs. Use KeychainWrapper.standard to access the singleton instance.                                        

To use this wrapper you need to import it in your project. For import write import SwiftKeychainWrapper in your project file.                                                                     

Usage

Here an example of storing value in a keychain is given below

KeychainWrapper.standard.set(“u[email protected]”, forKey: “email”)

Here an example of how to retrieve a stored value in a keychain is given below

let email = KeychainWrapper.standard.string(forKey: "email")

Here is an example of deleting string values from the keychain

KeychainWrapper.standard.removeObject(forKey: "email")

Here is an example of deleting all stored values from the keychain

KeychainWrapper.standard.removeAllKeys()

Reference: https://developer.apple.com/documentation/security/certificate_key_and_trust_services/keys/storing_keys_in_the_keychain

That's all folks!