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From: Elmo on 28 Jan 2010 23:14
On Thu, 28 Jan 2010 16:01:32 +0000 (UTC), Mike S. wrote:

>>Since IMEI numbers are not unique
>
> If they are not unique, how can numerous countries use the IEMI# as the
> basis for reporting and blacklisting stolen phones?

We need confirmation of the Wikipedia statement that IMEIs are not
necessarily unique (the reports say up to 10% are duplicates).

Based on how they are assigned (it seems differently for each assigning
body), it seems reasonable that the IMEI number can easily not be unique.

You can still blacklist the number. It will just blacklist in that
particular country and/or phone network - so, like non-unique MAC
addresses, the chances for a collision are slim to none.

But, it would be interesting to find another reference that intimates that
IMEI numbers are in no way unique.
From: Elmo on 31 Jan 2010 23:35
On Fri, 29 Jan 2010 04:14:45 +0000 (UTC), Elmo wrote:

> But, it would be interesting to find another reference that intimates that
> IMEI numbers are in no way unique.

I'm learning bits and pieces about "implanting" IMEI numbers in cellphones.

Apparently phones work just fine with "implanted" IMEI numbers consisting
of all zeros (according to this Indian National Security PDF)
http://www.dot.gov.in/as/2008/Requirements%20for%20Natilonal%20Security_10.10.08.pdf

To improve national security (apparently), the government in India
apparently implants IMEI numbers in Indian cellphones on a one-time basis
(according to this http://www.msai.in/gii.html).

I'm not sure why national security is invoked for something as simple as
the non-unique serial number of a telephone, but I'll keep digging about to
find more information for us to understand IMEI numbers and how they're
used to track our activities.
From: Dennis Ferguson on 2 Feb 2010 01:08
On 2010-02-01, Elmo <dcdraftworks(a)Use-Author-Supplied-Address.invalid> wrote:
> On Fri, 29 Jan 2010 04:14:45 +0000 (UTC), Elmo wrote:
>
>> But, it would be interesting to find another reference that intimates that
>> IMEI numbers are in no way unique.
>
> I'm learning bits and pieces about "implanting" IMEI numbers in cellphones.
>
> Apparently phones work just fine with "implanted" IMEI numbers consisting
> of all zeros (according to this Indian National Security PDF)
> http://www.dot.gov.in/as/2008/Requirements%20for%20Natilonal%20Security_10.10.08.pdf

I was in India at the end of November and got a bunch of text messages
from the local carrier about this, I think phones without valid
IMEI numbers were banned on December 1, 2009.

The phones with all-zeros IMEIs, or no IMEI number at all, were
almost all very, very low end phones manufactured in China. The
reason for this mentioned in the newspapers was that those phones
are sold with razor-thin margins and, given that the only bodies
issuing TACs at that point were the British (35) and American (01)
organizations which were thought too inconvenient and expensive
to deal with by the Chinese manufacturers, the manufacturers
didn't bother getting IMEI numbers for the phones and just sold
them without. The all-zero's IMEIs were programmed by the
manufacturers. China fixed this a couple of years ago by setting
up a local body for allocating TACs (86) and passing a law requiring
all phones manufactured there to have a valid IMEI (the GSMA also
began funding the British body, so it no longer charges). India
set up their own registry (91) to deal with existing phones which
needed an IMEI.

The GSMA guidelines, here

http://www.gsmworld.com/documents/DG06_3v7-Draft.pdf

require that the IMEI be difficult or impossible to change in all
phones manufactured since 2002 (apparently cheap Chinese phones
are an exception). If your phone is less than 8 years old and from
a reputable manufacturer it is very likely to have a unique IMEI and
you are unlikely to be able to do anything about that. Since US
GSM carriers now sometimes charge different prices for the same
service (e.g. data plans) based on the phone's IMEI, I think they'd
be unhappy if the numbers could be changed.

> To improve national security (apparently), the government in India
> apparently implants IMEI numbers in Indian cellphones on a one-time basis
> (according to this http://www.msai.in/gii.html).
>
> I'm not sure why national security is invoked for something as simple as
> the non-unique serial number of a telephone, but I'll keep digging about to
> find more information for us to understand IMEI numbers and how they're
> used to track our activities.

Having phones with unique IMEI numbers makes it very slightly more
difficult for people who might want to hide their identity by
swapping SIM cards; they need to get a new phone as well.

It is also possible that India wants to be able to tie the IMEI
number to the owner of each phone used in the country. Like many
countries they are now quite strict about identifying the owners
of SIM cards (I had to fill out a form with my personal details and
provide a picture and copies of my passport and visa to get one),
and since that card was used in my phone I guess the phone might be
tied to me as well now, so they'll know who to ask if they find my phone
being used for something they are interested in.

I did get two text messages telling me my own phone's IMEI was invalid
and I needed to pay 175 rupees to fix it, but they didn't cut me
off after December 1 so I assume that was just a mistake (or scam)
by the operator.

Dennis Ferguson
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