17
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
1 IMEI vs. IMEISV
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
2 ===============
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
3
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
4 There is a subtle distinction between an IMEI and an IMEISV. The first 14
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
5 digits are the same between the two: the supposedly-world-unique number of a
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
6 given piece of hardware. In a traditional IMEI 15-digit number the significant
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
7 14 digits are followed by a Luhn check digit, whereas an IMEISV has 16 digits:
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
8 the 14 significant digits of the IMEI, *no* Luhn check digit, and two digits of
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
9 "software version".
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
10
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
11 It is up to device manufacturers and firmware designers to decide whether or
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
12 not to store the Luhn check digit in the GSM device's flash or EEPROM or
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
13 whatever, but it is not sent over the air: instead the IMEISV is sent. It
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
14 appears that the GSM standard authors' intent was that the IMEI part is stored
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
15 immutably in each manufactured device whereas the SV digits are added by the
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
16 running firmware to indicate its version, but the IMEI handling scheme
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
17 implemented in TI's reference firmware and retained by many of the TI-based GSM
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
18 device manufacturers (at least FIC/Openmoko and Foxconn/Pirelli) dispenses away
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
19 with the IMEI vs. IMEISV distinction.
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
20
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
21 IMEI storage and retrieval in TI's reference firmware
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
22 =====================================================
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
23
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
24 When running on the plain Calypso as opposed to Calypso+, TI's TCS211 reference
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
25 firmware supports two ways of storing and retrieving the IMEI: obfuscated and
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
26 unobfuscated. In both schemes the IMEI datum is stored as a file in the
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
27 device's flash file system (FFS), and even though the FFS filename calls it the
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
28 IMEI, the content of this file is really treated as the IMEISV: 16 digits are
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
29 stored, the firmware function responsible for reading the IMEI datum out of FFS
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
30 and passing it on to the rest of the fw is called cl_get_imeisv(), the code in
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
31 this function does not transform the 16 digits in any way, and the downstream
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
32 recipients of these digits treat them as the IMEISV.
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
33
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
34 The two specific schemes offered by TCS211 fw are as follows:
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
35
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
36 In the unobfuscated scheme (FF_PROTECTED_IMEI not defined), the so-called IMEI
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
37 but really IMEISV is stored in an FFS file named /pcm/IMEI. The file is 8 bytes
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
38 long, each byte stores two IMEISV digits, and the order of the digits within
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
39 each byte is reversed relative to the natural order: first the least significant
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
40 nibble is used, then the most significant nibble.
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
41
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
42 In the obfuscated scheme (FF_PROTECTED_IMEI is defined), the so-called IMEI but
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
43 really IMEISV is stored in an FFS file named /gsm/imei.enc. The file is 16
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
44 bytes long: the first 8 bytes store the 16-digit IMEISV encrypted with DES,
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
45 using the Calypso die ID as the key, and the last 8 bytes store that Calypso die
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
46 ID DES-encrypted with itself. Underneath the obfuscation, the 16 IMEISV digits
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
47 are stored in the 8 bytes in the natural order: first the most significant
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
48 nibble is used, then the least significant nibble.
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
49
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
50 IMEI storage and retrieval schemes implemented by device manufacturers
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
51 ======================================================================
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
52
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
53 Openmoko devices use the unobfuscated IMEI storage method unchanged from TI's
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
54 reference fw: the factory-assigned IMEI is stored in an FFS file named
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
55 /pcm/IMEI, and that is where the original mokoN firmwares look for it. Further
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
56 blurring the distinction between the IMEI and the IMEISV, the 16 digits stored
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
57 in /pcm/IMEI (which the fw treats as the IMEISV) were factory-programmed as the
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
58 15-digit IMEI (with the Luhn check digit) with an appended 0, i.e., the SV
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
59 digits get set to x0 where x is the Luhn check digit.
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
60
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
61 Foxconn, the makers of the Pirelli DP-L10, have used the obfuscated version of
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
62 TI's IMEI handling mechanism instead, with an additional twist: instead of
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
63 storing the 16-byte encrypted datum in /gsm/imei.enc in FFS, they have moved it
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
64 into their own factory data record stored in a non-FFS sector of the flash.
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
65 The content of the 16 digits treated as the IMEISV by the G23M component of the
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
66 fw is the same as Openmoko's: 15-digit IMEI with the Luhn check digit followed
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
67 by a 0 digit.
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
68
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
69 Compal, the makers of Motorola C1xx phones, have similarly moved their IMEI out
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
70 of FFS into their own proprietary flash data structures, and we have never
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
71 decoded the latter, hence we don't know exactly where and how their IMEI is
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
72 stored. If you wish to run FreeCalypso firmware on these phones, you have to
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
73 set your own IMEISV for our fw even if you are not seeking to make it different
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
74 from the factory-assigned one, as we don't know how to retrieve the latter.
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
75
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
76 Changing the IMEI
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
77 =================
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
78
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
79 When someone says that they wish to change the IMEI on their phone, they need
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
80 to be a little clearer as to what they really mean, as there are two possible
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
81 interpretations of the just-stated wish:
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
82
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
83 1. Transmitting a different IMEISV toward the network by running your own
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
84 firmware on the device,
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
85
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
86 or
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
87
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
88 2. Changing the IMEI seen by the device's original proprietary firmware.
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
89
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
90 Interpretation 1 is much easier than interpretation 2: when you are writing your
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
91 own firmware for an "alien" GSM device (hardware designed and made by someone
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
92 other than you), it is much easier to just set your own IMEISV and be done with
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
93 it than to figure out how to retrieve the factory-assigned one. Thus those
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
94 device manufacturers who try to make it more difficult to change their IMEIs
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
95 are actually creating the opposite effect: people will just set their own IMEISV
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
96 when running their own fw on their hw.
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
97
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
98 Openmoko devices are a rare exception in that if you write your own IMEISV into
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
99 /pcm/IMEI in FFS, your new IMEISV will take effect not only with FreeCalypso
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
100 firmware, but also with the legacy mokoN fw versions, because they all look in
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
101 /pcm/IMEI. The same does NOT hold with Compal/Motorola or Foxconn/Pirelli
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
102 phones, however: if you wish to change their IMEI to be seen by their original
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
103 proprietary firmwares, you are on your own, as we do not currently have any
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
104 tools for accomplishing such a feat.
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
105
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
106 IMEI handling in FreeCalypso
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
107 ============================
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
108
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
109 The FreeCalypso family of projects has adopted the following IMEI storage and
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
110 retrieval scheme both for our own FreeCalypso-made hardware and for FreeCalypso
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
111 firmwares running on alien hardware: all of our firmware versions regardless of
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
112 target will look first in /etc/IMEISV, then in /pcm/IMEI when needing to obtain
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
113 the IMEISV for GSM operation. This is the new unified convention; previously
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
114 we used varying IMEISV retrieval schemes depending on the target and in
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
115 different FC firmware projects. The new unified convention is backward-
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
116 compatible with our previous schemes on every target.
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
117
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
118 The /etc/IMEISV file is a FreeCalypso invention. The file is 8 bytes long, and
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
119 stores the 16 digits of the IMEISV in the natural order: first the most
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
120 significant nibble is used, then the least significant nibble. This nibble
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
121 order makes the IMEISV number directly readable in a hex dump of the file, and
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
122 the filename /etc/IMEISV makes it clear that the last two digits are the SV and
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
123 are not required to be equal to the Luhn check digit and 0.
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
124
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
125 Both /etc/IMEISV and /pcm/IMEI can be written with the fc-fsio utility's
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
126 set-imeisv command:
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
127
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
128 set-imeisv fc XXXXXXXX-YYYYYY-ZZ # write /etc/IMEISV
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
129 set-imeisv pcm XXXXXXXX-YYYYYY-ZZ # write /pcm/IMEI
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
130
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
131 When working on Openmoko devices, we recommend writing your IMEISV into
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
132 /pcm/IMEI (set-imeisv pcm command) and not creating an /etc/IMEISV file: newer
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
133 FC firmware versions will look in both locations, but older FC fw versions and
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
134 the legacy mokoN ones look only in /pcm/IMEI. On all other targets we recommend
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
135 using the new /etc/IMEISV storage format, i.e., you should use the set-imeisv fc
|
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
changeset
|
136 variant.
|
