Biometric authentication is a crucial security feature that enables users to access their devices and applications using unique biological characteristics, such as fingerprints or facial recognition. In the Apple ecosystem, biometric authentication is implemented through technologies like Touch ID and Face ID. These features enhance security and provide a seamless user experience.

This article will guide you through the process of implementing biometric authentication in your iOS applications using Swift. We will cover the necessary steps to configure your app to use Touch ID and Face ID for authentication.

Examples:

Example 1: Setting Up Biometric Authentication in an iOS App

1. Import LocalAuthentication Framework: To use biometric authentication, you need to import the LocalAuthentication framework in your Swift file.

   import LocalAuthentication

2. Create an Authentication Context: Create an instance of LAContext, which provides the interface to evaluate authentication policies.

   let context = LAContext()
   var error: NSError?
   
   // Check if biometric authentication is available
   if context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error) {
      // Biometric authentication is available
   } else {
      // Biometric authentication is not available
      print(error?.localizedDescription ?? "Unknown error")
   }

3. Evaluate the Policy: Use the evaluatePolicy method to prompt the user for biometric authentication.

   context.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: "Authenticate to access your account") { success, authenticationError in
      DispatchQueue.main.async {
          if success {
              // Authentication was successful
              print("Authentication successful")
          } else {
              // Authentication failed
              print(authenticationError?.localizedDescription ?? "Failed to authenticate")
          }
      }
   }

Example 2: Handling Authentication Errors

It's essential to handle potential errors that may occur during the authentication process. Here is how you can manage different error scenarios:

context.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: "Authenticate to access your account") { success, authenticationError in
    DispatchQueue.main.async {
        if success {
            // Authentication was successful
            print("Authentication successful")
        } else {
            // Authentication failed
            if let error = authenticationError as NSError? {
                switch error.code {
                case LAError.authenticationFailed.rawValue:
                    print("Authentication failed")
                case LAError.userCancel.rawValue:
                    print("User canceled the authentication")
                case LAError.userFallback.rawValue:
                    print("User chose to use fallback authentication")
                case LAError.biometryNotAvailable.rawValue:
                    print("Biometric authentication is not available")
                case LAError.biometryNotEnrolled.rawValue:
                    print("Biometric authentication is not enrolled")
                case LAError.biometryLockout.rawValue:
                    print("Biometric authentication is locked out")
                default:
                    print("Unknown error: \(error.localizedDescription)")
                }
            }
        }
    }
}

Example 3: Fallback Authentication

In some cases, users may prefer to use a passcode instead of biometric authentication. Here is how you can provide a fallback option:

context.evaluatePolicy(.deviceOwnerAuthentication, localizedReason: "Authenticate to access your account") { success, authenticationError in
    DispatchQueue.main.async {
        if success {
            // Authentication was successful
            print("Authentication successful")
        } else {
            // Authentication failed
            print(authenticationError?.localizedDescription ?? "Failed to authenticate")
        }
    }
}