How to generate a valid IMEI number

Meanwhile, at the alt.internet.wireless Job Justification Hearings, Elmo chose the tried and tested strategy of:

(Found with Google in about 10 seconds).

What I actually gleaned from the previous post is that AT&T doesn't care. If you change a single digit in a valid 15-digit IMEI, as you said you did, you get an invalid one. AT&T took it anyway.

Dennis Ferguson

Yup. What happened was I've been paying about $145/month for the Blackberry with world access and full data and blackberry enterprise and whatever.

Then my needs changed, about a year and a half into the plan. I called 611 from my Blackberry to remove all the stuff I no longer needed but the customer support gal wouldn't get rid of the data plan solely because it was a blackberry (not, I remind you, not because they subsidized it as they subsidize all phones initially).

I argued that I could easily move the SIM card to an unlocked Motorola RAZR and she said if I did that, then I could remove the data plan. I told her then remove it, and she said no, because I was using the blackberry.

So I asked for her supervisor. When the supervisor came on line, she already knew what I wanted. She told me I could only remove the data plan if I changed the phone so I told her I changed the phone right then and there. I was with a friend so we took out his Motorola RAZR and changed the last digit. She didn't seem to care. She dropped the data plan.

The only drawback I can see is she also dropped the warranty but that's a small price to pay to save about 50 bucks a month (taxes and stuff included).

This forum only discusses how to calculate the checksum; I was looking for the whole IMEI number generation.

For example, to generate a valid MAC address is easy, if you have a table of manufacturers' assigned OIDs.

The most interesting fact I learned from that article is that 10% of all the IMEI numbers out there are not unique!

I also learned from that article that, like the MAC address on a PC, one can change the IMEI number on a particular telephone (if they know how).

Again, similar to MAC addresses, it looks like IMEI numbers are allocated to the manufacturer by a standards body.

So, the good news is that I can probably find software to generate a valid IMEI number given some input parameters (sort of like what MacMakeUp or SimpleMac or MadMacs does for the PC).

I'll summarize the algorithm separately as this post is getting long.

Based on that article, IMEI numbers are not necessarily unique and the IMEI number of a cellphone can be changed (similar to MAC addresses in a PC).

Also very interesting is that the checksum (last digit) is "never transmitted". Hmmmmmm.... it's interesting that the last digit is not "seen" by AT&T's hardware ...

I'll try to summarize the IMEI generation steps in a later post because the first step in generating a valid 15-digit IMEI number for any cellphone is understanding what the number means.

The Wikipedia article says the last digit (checksum) isn't transmitted to AT&T, so, maybe that's why it didn't matter. Dunno.

Since IMEI numbers are not unique and since any cellphone can have it's IMEI number changed, here's the algorithm for a typical year 2004 15-digit IMEI number "AA-BBBBBB-CCCCCC-D", where ...

AA-The first two digits apparently indicate the issuing agency.

BBBB-The next four digits seem to indicate the "allocation number" by that issuing agency.

BB-The next two digits indicate the Final Assembly Code (i.e., the location of the manufacturers' manufacturing facility).

CCCCCC-The next six digits are the serial number of the telephone.

D-the last digit is the checksum digit, which is ALWAYS transmitted to the network as a 0.

Apparently that non-transmitted checksum is calculated by adding the 1st +

2(2nd) + 3rd + 2(4th) + 5th + 2(6th) + 7th + 2(8th) + 9th + 2(10th) + 11th

• 2(12th) + 13th + 2(14th) digits and then adding a 15th digits such that the resulting addition ends up with a zero on the end.

One way to generate a valid IMEI number is to enter numbers into this website until they generate the type of cellphone you want to emulate:

Here's a list of valid Final Assembly Codes to help in the generation of a valid IMEI number. I don't see RIM here so this list must not be all inclusive.

FAC Code

01 AEG 02 AEG 07 Motorola 40 Motorola 10 Nokia 20 Nokia 30 Ericsson 40 Siemens 41 Siemens 44 Siemens 50 Bosch 51 Sony, Siemens, Ericsson 60 Alcatel 61 Ericsson 65 AEG 70 Sagem 75 Dancall 80 Philips 85 Panasonic

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.

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)

To improve national security (apparently), the government in India apparently implants IMEI numbers in Indian cellphones on a one-time basis (according to this 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.

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

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.

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