What are security checklist while developing the iOS banking applications?

Answer:

Developing an iOS banking application requires rigorous security measures to protect user data and financial information. Here’s a comprehensive security checklist for iOS banking app development:

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1. Data Security

• Encryption:
  • Use AES-256 for sensitive data encryption at rest.
  • Use TLS 1.3 for secure data transmission.
• Keychain Storage:
  • Store sensitive information like user credentials securely in the iOS Keychain.
• Sensitive Data Protection:
  • Avoid storing sensitive data (e.g., PIN, password) in UserDefaults or plain text.
  • Use Secure Enclave for biometric authentication-related data.

---

2. Authentication and Authorization

• Biometric Authentication:
  • Integrate Face ID/Touch ID for user authentication.
  • Fall back to secure passcodes if biometrics fail.
• Multi-Factor Authentication (MFA):
  • Enable MFA for added security during critical operations (e.g., transactions).
• OAuth 2.0/OpenID Connect:
  • Implement secure authentication mechanisms for third-party logins.

---

3. Network Security

• Certificate Pinning:
  • Prevent MITM (Man-In-The-Middle) attacks by pinning certificates.
• HSTS (HTTP Strict Transport Security):
  • Enforce HTTPS connections by enabling HSTS.
• Secure API Endpoints:
  • Use strong API authentication mechanisms like API keys or tokens.

---

4. App Security

• Code Obfuscation:
  • Use tools like ProGuard or third-party solutions to obfuscate the app code.
• Jailbreak Detection:
  • Detect if the app is running on a jailbroken device and block access.
• Runtime Protection:
  • Use runtime anti-tampering libraries to prevent reverse engineering.
• Disable Debugging Tools:
  • Ensure the app blocks debugging frameworks like Frida and Cycript.

---

5. User Session Management

• Session Timeout:
  • Automatically log out users after a period of inactivity.
• Token Expiry:
  • Use short-lived access tokens and refresh tokens for session handling.
• Secure Logout:
  • Clear all session data securely during logout.

---

6. Secure Storage

• Keychain Access Groups:
  • Share data securely between apps using keychain access groups.
• App Group Containers:
  • Use app group containers for shared data across app extensions.
• Prevent Backups:
  • Exclude sensitive files from iCloud or iTunes backups (NSURLIsExcludedFromBackupKey).

---

7. Secure Communication

• Custom URL Schemes:
  • Validate and sanitize data sent through custom URL schemes to avoid misuse.
• WebView Security:
  • Use WKWebView instead of UIWebView.
  • Disable JavaScript unless necessary.

---

8. Compliance and Privacy

• GDPR/CCPA Compliance:
  • Ensure data collection aligns with GDPR, CCPA, and local regulations.
• User Privacy:
  • Display clear privacy policies.
  • Obtain user consent before accessing sensitive information (e.g., location, contacts).

---

9. Security Testing

• Penetration Testing:
  • Conduct periodic penetration tests to identify vulnerabilities.
• Static and Dynamic Analysis:
  • Use tools like SonarQube and OWASP ZAP for static and dynamic security analysis.
• OWASP Mobile Top 10:
  • Test the app against OWASP Mobile Top 10 vulnerabilities.

---

10. Miscellaneous

• Analytics and Logs:
  • Avoid logging sensitive information like user credentials and session tokens.
• Version Updates:
  • Regularly update third-party libraries to patch known vulnerabilities.
• Secure App Distribution:
  • Use the Apple App Store for app distribution. Avoid distributing apps outside the official store.

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Adhering to these practices ensures robust security in iOS banking applications, protecting both the user and the financial institution. Let me know if you need deeper details on any of these points!

Write a function which returns the minimum, maximum, average banking transaction amount. How you can optimise those functions for execution time and in terms of memory allocation?

 Answer: 

Using higher-order function:

import Foundation

// Function to calculate min, max, and average transaction amounts

func calculateTransactionStats(transactions: [Double]) -> (min: Double?, max: Double?, average: Double?) {
    guard !transactions.isEmpty else {
        return (nil, nil, nil) // Handle empty array case
    }
    
    let minTransaction = transactions.min()
    let maxTransaction = transactions.max()
    let averageTransaction = transactions.reduce(0, +) / Double(transactions.count)
    
    return (minTransaction, maxTransaction, averageTransaction)
}

Without using higher-order function (optimised code in terms of memory allocation and execution time): 

import Foundation

// Function to calculate min, max, and average without using higher-order functions

func calculateTransactionStats(transactions: [Double]) -> (min: Double?, max: Double?, average: Double?) {

    guard !transactions.isEmpty else {

        return (nil, nil, nil) // Handle empty array case

    }

    var minTransaction = transactions[0]

    var maxTransaction = transactions[0]

    var total = 0.0

    

    for transaction in transactions {

        if transaction < minTransaction {

            minTransaction = transaction

        }

        if transaction > maxTransaction {

            maxTransaction = transaction

        }

        total += transaction

    }

    

    let averageTransaction = total / Double(transactions.count)

    return (minTransaction, maxTransaction, averageTransaction)

}

// Example usage

let transactions = [1200.5, 450.0, 2300.0, 560.0, 890.75]

let stats = calculateTransactionStats(transactions: transactions)

print("Minimum Transaction: \(stats.min ?? 0)")

print("Maximum Transaction: \(stats.max ?? 0)")

print("Average Transaction: \(stats.average ?? 0)")

Optimisations Explained:

1. Single Loop:

   • In the original implementation, no redundant loops are present since everything is already computed in a single loop. This is efficient and does not require optimization.

2. Avoid Extra Memory Allocation:

   • We are only using three variables (minTransaction, maxTransaction, and total) to store intermediate values.
   • No extra arrays or data structures are created during computation.

3. Direct Access:

   • We directly access elements of the array using a for loop without calling methods like min(), max(), or reduce(). This avoids any extra function calls or higher-order function overhead.

4. Efficient Guard Clause:

   • The guard statement ensures the function exits early if the input array is empty, avoiding unnecessary computations.

Additional Suggestions for Large Datasets:

1. Use Parallel Processing for Large Datasets:

   • If the dataset is very large, you can divide the array into chunks and process each chunk in parallel using concurrency (e.g., GCD or Swift's async/await) to compute partial min, max, and sum. Combine these partial results in the end.
   • However, note that this may only be beneficial when the array size is extremely large, as parallelism introduces its own overhead.

2. Precision Control:

   • For very large datasets or high precision requirements, consider using floating-point types like Decimalinstead of Double to avoid precision errors.

3. Memory Optimization:

   • If you don’t need to keep the original array after processing, you can work directly with the same array, reducing memory usage (e.g., use inout for array processing).

Final Notes on Performance:

• The optimized function already computes the required results in O(n) time complexity with O(1) additional memory usage.
• These optimizations ensure that the function is fast and uses minimal resources for typical use cases.

Will below code be compiled successfully? Explain why?

 Code: 

class MainClass {
    func mainClassFunction() {
        print("mainClassFunction")
    }
}
class SubClass: MainClass {
    func subClassFunction() {
        print("subClassFunction")
    }
}
extension SubClass {
    override func mainClassFunction() {
        print("extension")
    }
}

Answer: Will Not compile.

The provided code will not compile. 

Reason:

In Swift, extensions cannot override methods that are defined in the superclass. Overrides are a feature of subclassing and must be declared within the subclass itself, not in an extension. 

Explanation:

1. The MainClass Definition:

   - The MainClass contains a method mainClassFunction().

2. The SubClass Definition:

   - The SubClass inherits from MainClass and can override mainClassFunction() if needed (but doesn't in this code).

3. The Extension:

   swift

   extension SubClass {

       override func mainClassFunction() {

           print("extension")

       }

   }

   

   Here, the extension attempts to override the mainClassFunction() from MainClass. This results in a compiler error because Swift does not allow method overrides in extensions.

   This restriction exists because extensions are intended to add functionality, not alter or replace existing functionality of the class hierarchy.

Correct Approach:

To override mainClassFunction(), the override must be declared directly within the SubClass:

swift

class SubClass: MainClass {

    override func mainClassFunction() {

        print("extension")

    }

}

Conclusion:

The code will not compile because overriding a method in an extension is not allowed in Swift. Overrides must occur within the subclass itself.

What will be output for following code?

 Code: 

enum Test: Int 
{      
    case VeryOld = -1      
    case Old      
    case Current     
    case Future 
 }  
let testEnum = Test.Current  
print("testEnum.rawValue: \(testEnum.rawValue)")  

Output:

testenum.rawvalue: 1

Difference between assign and retain in iOS

In the context of memory management in programming, particularly in Objective-C (though less relevant in modern Swift), "assign" and "retain" are related to the property attributes used in the declaration of object properties.

1. Assign:

   • 
     
   • In the context of Objective-C, the assign attribute is used for simple assignments and is often associated with primitive types or non-Objective-C objects.
   • When you declare a property with the assign attribute, you're saying that the property will just take the value assigned to it without affecting the reference counting of the object.
   • 
     
   • @property (assign) NSInteger someInteger;
   • 
     
   • For objects, assigning does not increase the retain count, so if the assigned object is deallocated elsewhere, you might end up with a dangling pointer.

2. 
   

   Retain:

   • 
     
   • The retain attribute, on the other hand, is used when you want to claim ownership of an object. It increases the retain count of the object, indicating that you want to keep a reference to it.
    
   @property (retain) NSString *name;
   
   
   • 
     
   • When using retain, it's your responsibility to release the object when you're done with it. This is crucial to avoid memory leaks.
   • 
     
   • [name release];
   • 
     
   • In modern Objective-C and Swift, Apple introduced Automatic Reference Counting (ARC), which essentially automates the reference counting process. In Swift, you generally use strong instead of retain, and the memory management is handled by the ARC.

In summary, the key difference is that assign is used for non-object types and doesn't affect the reference counting of objects, while retain (or strong in Swift) is used for objects, and it does increase the retain count, indicating ownership. With ARC in Swift, the need to manually specify assign or retain has diminished, as ARC takes care of many memory management tasks automatically.AI.

Dependency injection in Swift

 Dependency injection (DI) is a design pattern in software development that promotes the separation of concerns by allowing components to depend on abstractions rather than concrete implementations. In Swift, dependency injection is commonly used to achieve loosely coupled and easily testable code.

There are three main types of dependency injection:

1. Constructor Injection: Dependencies are injected through the class's initializer.

2. Method Injection: Dependencies are injected through methods of the class.

3. Property Injection: Dependencies are injected through properties of the class.

Let's look at an example using constructor injection in Swift:

// Protocol defining the dependency protocol DataService { func fetchData() -> String } // Concrete implementation of the DataService protocol class RemoteDataService: DataService { func fetchData() -> String { return "Data from remote service" } } // Class that depends on DataService through constructor injection class DataManager { let dataService: DataService init(dataService: DataService) { self.dataService = dataService } func processData() -> String { let data = dataService.fetchData() return "Processed: \(data)" } } // Example of using the DataManager with dependency injection let remoteDataService = RemoteDataService() let dataManager = DataManager(dataService: remoteDataService) let result = dataManager.processData() print(result) // Output: Processed: Data from remote service

In this example:

• DataService is a protocol that defines the contract for fetching data.
• RemoteDataService is a concrete implementation of DataService.
• DataManager is a class that depends on DataService through its initializer.

This setup allows you to easily switch the implementation of DataService without modifying DataManager. For example, you could create a LocalDataService implementing DataService and use it with DataManager without changing the DataManager class.

class LocalDataService: DataService { func fetchData() -> String { return "Data from local storage" } } let localDataService = LocalDataService() let dataManagerWithLocalData = DataManager(dataService: localDataService) let resultLocal = dataManagerWithLocalData.processData() print(resultLocal) // Output: Processed: Data from local storage

This flexibility is especially useful for testing, as you can easily substitute real implementations with mock implementations for testing purposes.AI.

Difference between App Store Binary Rejection and Metadata rejection

When submitting an application to the App Store, developers may encounter two types of rejections: App Store Binary Rejection and Metadata Rejection. Understanding the difference between these rejections is essential for iOS developers using Xcode to maximize their chances of successfully getting their apps approved.

App Store Binary Rejection refers to the rejection of the compiled binary code that forms the application. This rejection can stem from numerous reasons, such as memory leaks or violations of Apple's App Store Review Guidelines. Memory leaks occur when an app fails to release dynamically allocated memory, resulting in wasted memory resources and potential crashes. To mitigate memory leaks, developers must carefully use memory allocation and deallocation mechanisms provided by iOS and Xcode, such as ARC (Automatic Reference Counting) or manual memory management.

On the other hand, Metadata Rejection deals with issues related to the app's information and presentation on the App Store. It primarily focuses on the textual and visual components, including the app's name, description, screenshots, keywords, and other metadata. Common reasons for metadata rejection can include misleading app descriptions or inappropriate screenshots that do not accurately represent the actual app functionalities.

To avoid both types of rejections, it is imperative for developers to pay attention to detail during the development and submission process. After addressing potential memory leaks by employing proper memory management practices, developers must also ensure that the app's metadata accurately reflects its functionalities and adheres to Apple's guidelines. By debugging their code thoroughly using instruments provided by Xcode, developers can identify and resolve any memory leaks, while adhering to Apple's App Store Review Guidelines can prevent metadata rejection.

In conclusion, developers using Xcode to create iOS apps must be aware of the distinction between App Store Binary Rejection and Metadata Rejection. By addressing memory leaks, adhering to Apple's guidelines, and carefully preparing app metadata, developers can increase the chances of getting their apps approved on the App.AI.

Difference between normal function and function ending throw

Function ending with throw can throw error but normal function can not throw error it can just return value.

Lets take example :

1. Custom error enum

enum ErrorsToThrow: Error {

    case fileNotFound

    case fileNotReadable

    case fileSizeIsTooHigh

}

2. Make function which can throw error

func readFiles(path:String) throws  ->String {

        if path == "" {

            throw ErrorsToThrow.fileNotFound

        }

        return "Data from file"

    }

3. Calling readFiles function

   do {

            let dataFromString = try? readFiles(path: "")

            print(dataFromString)

        } catch ErrorsToThrow.fileNotFound {

            print("error generated1")

        } catch ErrorsToThrow.fileNotReadable {

            print("error generated2")

        } catch ErrorsToThrow.fileSizeIsTooHigh {

            print("error generated3")

        } catch {

                print("error")

        }

Now, let's analysis.

1. If in #2, function is not ending with throws can not throw error. But our function can throw error.
2. In #3, we have used try?, so if readFiles function return nil instead of throwing error. So in our case print(dataFromString) statement executed and it will nil means printing nil.

3. If try! is written and if function throw error, then fatal error will be occured and program will be crashed as we ensure that error will not occur by putting ! .
4. So if we want to execute catch statement then we have to use only try . try always used with do-catch.
5. try? and try! does not need do-catch block.

Write a program to define closure which accepts string and return integer.

 Write a closure that accepts string and return length of string(which is integer) :

let simpleClosure:(String) -> (Int) = { name in 

    return name.count

}

let result = simpleClosure("Hello World")

print(result)

Identifying Memory Leaks using the Xcode

Identifying Memory Leaks in Xcode with Memory Graph Debugger is a great way to make application leakage proof. When it comes to detecting memory leaks in iOS development using Xcode, there are a few steps you can follow. Memory leaks can lead to performance issues, crashes, and an overall degraded user experience. Therefore, it is crucial to address and resolve them.

1. Enable the Memory Debugging Tools:

   - Open your Xcode project and go to the "Product" menu.

   - Select "Scheme" and then click on "Edit Scheme."

   - In the left sidebar, select "Run" and then navigate to the "Diagnostics" tab.

   - Enable the "Memory Management" option and close the scheme editor.

2. Run the App with the Leaks Instrument:

   - Build and run your iOS app in the Xcode simulator or on a physical device.

   - Go to the "Product" menu and select "Profile."

   - Choose the "Leaks" instrument.

   - Observe the instrument while interacting with your app to detect any memory leaks.

   - If any leaks are found, it will be indicated in the "Allocations List" and "Leaks List" panels.

3. Analyze the Detected Leaks:

   - Click on the leaks listed in the "Leaks List" panel to review them in detail.

   - The "Allocations Summary" panel will show you the memory allocations and deallocations for each object.

   - Analyze the call stack to identify the source of the leak.

   - Pay attention to any objects that are not being deallocated when they should be.

4. Diagnose the Memory Leak:

   - Understanding the code responsible for the memory leak is key to finding a solution.

   - Use the call stack information and Xcode's debugging tools to trace back to where the leaked object is created or retained.

   - Review variables and references that may be keeping the object from being released.

   - Common causes of memory leaks include strong reference cycles, forgotten timers, delegates not set as weak, or improper use of closures.

5. Fix the Memory Leak:

   - Once you've identified the source of the memory leak, take appropriate actions to fix it.

   - Ensure that objects are properly deallocated by removing any unnecessary strong references.

   - Consider using weak or unowned references where appropriate.

   - Review your code for strong reference cycles and break them using capture lists or weak/unowned references.

   - Validate that the memory leak is resolved by re-running the app and using the Leaks instrument again.

By following these steps, you can effectively detect and fix memory leaks in your Xcode project. Regularly checking for and resolving memory leaks will result in a more stable and efficient iOS .