Unique Identifier for the iOS Devices

Why to Identify devices?

Santosh BotreFollow

Jun 21, 2017

• Did this device already consume a free trial?
• Has this device paid for content but not linked that purchase to an account?
• Was this device previously enrolled for offer by user?

What different approaches, we are aware and using it in our implementation?

1. Get a unique device ID and store that on the server. Since UDIDs are no longer allowed, that’s out.

[[UIDevice currentDevice] uniqueIdentifier]

2. Use something like the advertising ID. Trouble is, user can reset that and get a new one. Used only for serving advertisement.

3. Use something like vendor identifier. Uniquely identifies the device to the app’s vendor. The value changes when user deletes all the vendor’s apps from the device and reinstalls one or more of them.

4. Write a unique ID into the keychain or user preferences. User can delete app, reinstall, and redeem item again.

NSUUID *UUID = [NSUUID UUID];

NSString* stringUUID = [UUID UUIDString];

5. Rely on user login. But then the user can create a dummy account and keep redeeming multiple times.

To get more information you can check http://nshipster.com/uuid-udid-unique-identifier/

What’s new?

Apple has come up with the DeviceCheck framework in iOS 11.

Access per-device, per-developer data that your associated server can use in its business logic.

Using DeviceCheck API’s, in combination with a server-to-server APIs, developer can set and query two bits of data per device. It will also maintain the user privacy, by not disclosing any user or device information, which is the priority point for every Apple user and most point of concern of every mobile user.

NOTE: Developer are still responsible for keeping track of whether users has already redeemed offers that you have provided.

Use DeviceCheck APIs to ensure that this is a device which has been aligned to one user so that same device cannot be used with different users to redeem the promotions/offers.

Your app should use the DeviceCheck APIs to generate an ephemeral token that identifies a device. Your associated server combines this token with an authentication key that you receive from Apple and uses the result to request access to the per-device bits.

Let’s go steps by steps,

1. Query for token — Use DCDevice class has a generateToken method which will generate the token.

2. Send token to app server — Send received token to your application server.

3. Set two bits — Application server will responsible for sharing this token and set the bit value.

{

“device_token” : “wlkCDA2Hy/CfMqVAShslBAR/0sAiuRIUm5jQg0a…”

“transaction_id” : “5b737ca6-a4c7–488e-b928–8452960c4be9”,

“timestamp” : 1487716472000,

“bit0” : true,

“bit1” : false

}

4. Delete Application — Delete the application from device

5. Reinstall Application

6. Query for token

7. Send token to app server

8. Query two bit — Request to Apple to query bit state

{

“device_token” : “wlkCDA2Hy/CfMqVAShslBAR/0sAiuRIUm5jQg0a…”

“transaction_id” : “5b737ca6-a4c7–488e-b928–8452960c4be9”,

“timestamp” : 1487716472000

}

9. Response from Apple server –

{

“bit0” : true,

“bit1” : true,

“last_update_time”: “2017–06”

}

//***************************************************************//

Class: DCDevice

This class represent the device and has only three methods as mentioned below,

class var current: DCDevice

The device for which to perform the check.

var isSupported: Bool

A Boolean value indicating whether the DeviceCheck APIs are available on the current device.

func generateToken(completionHandler: (Data?, Error?) -> Void)

Generates a token that identifies the current device.

Generate a new device token that can be used to get/set the persistent bits for this device. This call generates a new value every time.

//***************************************************************//

Reference:

WWDC 2017 — Session 702 — iOS, macOS, tvOS, watchOS

https://developer.apple.com/videos/play/wwdc2017/702/

https://developer.apple.com/documentation/devicecheck/accessing_and_modifying_the_per_device_data