Android Tutorial Android Device Unique ID - Alternative to PhoneId

Erel · Feb 7, 2012

This is an old tutorial. It will not work on new versions of Android. You should either generate a random value when the app starts for the first time or use the advertising id: https://www.b4x.com/android/forum/threads/advertising-id.101050/#content

This tutorial is based on the following blog post: Identifying App Installations | Android Developers Blog

The standard way to get a unique id is using PhoneId.GetDeviceId. However this method has several disadvantages:
- It requires the "android.permission.READ_PHONE_STATE" permission which is quite a sensitive permission.
- It doesn't work on devices without phone functionality.
- Apparently there is a bug in some devices which return the same id.

Starting from Android 2.3 there is a new field that returns a unique id and should work on all devices (without requiring any permission).

A general solution is to use this field for modern devices and to use a "fake" id for older devices. The fake id is randomly created when the application first runs.

Here is the code (requires the Reflection library):

B4X:

Sub Activity_Create(FirstTime As Boolean)
   Log(GetDeviceId)
End Sub

Sub GetDeviceId As String
   Dim r As Reflector
   Dim Api As Int
   Api = r.GetStaticField("android.os.Build$VERSION", "SDK_INT")
   If Api < 9 Then
      'Old device
      If File.Exists(File.DirInternal, "__id") Then
         Return File.ReadString(File.DirInternal, "__id")
      Else
         Dim id As Int
         id = Rnd(0x10000000, 0x7FFFFFFF)
         File.WriteString(File.DirInternal, "__id", id)
         Return id
      End If
   Else
      'New device
      Return r.GetStaticField("android.os.Build", "SERIAL")
   End If
End Sub

LucaMs · Mar 8, 2015

danijel said:
In that calculation you have nothing about possible matching.

You just calculated average distance between 2 neighbor numbers
from sorted list of 100,000 random generated intigers from interval [0, 2,147,483,648]

Lets say person X1 got one of 2,147,483,648 numbers.
Person X2 will get the same number with 1 / 2,147,483,648 chance = 0.0000000004656...
Person X2 will get different number with 2,147,483,647 / 2,147,483,648 chance = 0.9999999995343...

but we did't test all possible matching.
we tested only person X1 with person X2

we must test:

(X1 with X2) AND (X1 with X3) AND (X1 with X4) AND ... AND (X1 with X100,000)
AND
(X2 with X3) AND (X2 with X34 AND (X2 with X5) AND ... AND (X2 with X100,000)
AND
.
.
.
AND
(X99,999 with X100,000)

There is 4,999,950,000 possible matching (Binomial coefficient "100,000 choose 2")

So,
Probability that one pair have different numbers is:
2,147,483,647 / 2,147,483,648 chance = 0.9999999995343

Probability that all 4,999,950,000 pairs have different numbers is:
0.9999999995343^4,999,950,000=0.0974

If we take the complement of that:
Probability that there is at least one pair that have same numbers is:
1 - 0.0974 = 0.9026 = 90.26 %

Maybe contra intuitive but, like this,
similar "paradox" is that in group of just 23 people
greater chance is that there exist pair of two people that celebrates birthday
on same day than there doesn't exist such pair.
And here is 365 / 23 = 15.87 average days distance between 2 neighbor birthdays

Hope this helps!

Your answer is very complicated and at this time I have my usual headaches (also English does not help).

If you're right, a test is sufficient.

100 random pairs (or more, 100,000) and calculate how many of them are equal.

LucaMs · Mar 8, 2015

Is it correct?

danijel · Mar 8, 2015

LucaMs said:
Is it correct?

It runs 10 tests and count how many of them fails or not
total success will be around 50% (on 55,000)
total success will be around 10% (on 100,000)

WARNING: REALLY SLOW

LucaMs · Mar 8, 2015

danijel said:
It runs 10 tests and count how many of them fails or not
total success will be around 50% (on 55,000)
total success will be around 10% (on 100,000)

WARNING: REALLY SLOW

I did not understand.

The app calculates how many times two "Id" calculated at random are equal in proportion to the number of attempts. Probably never.

The probability that they are equal is 1 / (2 ^ 31)!

[using an emulator it is very fast, much less than one second]

[P.S. ops, you were referring to your project]

danijel · Mar 8, 2015

Ok, we don't understand each other.

The probability that two numbers are equal is 1 / (2 ^ 31)! - That's correct.
But if you have 100,000 users i'm trying to say that very often 99,998 users will get unique number and only 2 users will get the same number !
so not all users will have unique number and that Test is fail!
If happens that all 100,000 users get unique number that test is successful!

And i'm saying that in 90% cases Test will faill

Like in lottery... chance for one person to win is 1:15,000,000,000
but every month somebody score. How is that? - Lot's of people play.

LucaMs · Mar 8, 2015

I'm not so sure about this your statement:

"There is > 90% chance that 2 of 100,000 users will get the same number"

but you're right, it is preferable to use an alphanumeric code.

danijel · Mar 9, 2015

To be precise there is 90.25% chance that at least 2 of 100,000 users will get the same number.
Math is an exact science:

LucaMs · Mar 9, 2015

danijel said:
To be precise there is 90.25% chance that at least 2 of 100,000 users will get the same number.
Math is an exact science:

View attachment 32765

I'm not at all an expert in mathematics.

What is the operation represented by the position of the binomial coefficient?

(I do not know how to express well the question)

danijel · Mar 9, 2015

bin. coeff. is an exponent

http://goo.gl/oBTWTv

LucaMs · Mar 9, 2015

danijel said:
bin. coeff. is an exponent

http://goo.gl/oBTWTv

I supposed it but the Windows calculator does not allow me that calculation

Thanks

Peter Simpson · Apr 8, 2015

NeoTechni said:
I cheated. For my star trek app, I just generation a starship registry ID

ie: NCC-1701-D

J.L.Pickard would be pleased.

Shay · Sep 26, 2017

Using the code on first page (Erel) I cannot get ID from android tv device (getting 123456..)
and using the WIFI code I am getting 2:0:0:0:0... which is also not valid.
Any other way to get unique device id (especially from android tv devices?)

lemonisdead · Sep 26, 2017

Shay said:
Any other way to get unique device id

B4X:

Sub GetID As String
Dim P As Phone
Return P.GetSettings("android_id")
End Sub

?

NOPE : this one seems better doing https://b4x.com/android/forum/threads/unique-device-id-again.84329/#post-534249

Informatix · Sep 26, 2017

Working method to get an unique ID:
https://stackoverflow.com/a/14893618

lemonisdead · Sep 26, 2017

Informatix said:
Working method

I am a bit reserved on that : some devices change their MAC address on reboot. Just a thought

Shay · Sep 26, 2017

P.GetSettings("android_id")
seems to work great

Informatix · Sep 26, 2017

lemonisdead said:
I am a bit reserved on that : some devices change their MAC address on reboot. Just a thought

I agree that the MAC address is not reliable on some devices or under some circumstances (see https://www.b4x.com/android/forum/t...ternative-to-phoneid.14759/page-2#post-214618). In his post, the author says to put it to zeros if it is not usable, and warns that it cannot be used since Android 6.

Erel · Sep 27, 2017

Informatix said:
In his post, the author says to put it to zeros if it is not usable, and warns that it cannot be used since Android 6.

That's true. The MAC address is not available in Android 6+.

LucaMs · Sep 27, 2017

Informatix said:
Working method to get an unique ID:
https://stackoverflow.com/a/14893618

From that page:

Phone number/SIM card number (if available or just use zeros)
Android ID
Mac Address (if available or just use zeros)

So, if first and third element are zeros, you will use only Android ID. If it was enough, why should you use the other two?

Creating a rnd num (long) and saving it in the DirInternal is not a valid solution?

Informatix · Sep 27, 2017

LucaMs said:
From that page:

Phone number/SIM card number (if available or just use zeros)

Android ID

Mac Address (if available or just use zeros)

So, if first and third element are zeros, you will use only Android ID. If it was enough, why should you use the other two?

Creating a rnd num (long) and saving it in the DirInternal is not a valid solution?

I was in a bit of a hurry yesterday and I didn't elaborate. The idea to remember is that it is better to make an aggregate of several values than to simply rely on a single one. I implemented the proposed solution in my first application, My Playground, and I'm satisfied with it, but I didn't have a strict requirement.

Creating a random number that you save in a directory exposes you to the risk of hacking. Using the ID of someone else becomes pretty easy.

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