Data Recovery, Forensics 101, Mobile Devices

Geo-tag Forensics

Introduction

A geo-tagged image is an image which holds geographical identification metadata. This data consists of latitude and longitude co-ordinates (sometimes altitude also). Though there are some extremely powerful tools available for extracting geo-tag information from geo-tagged images but the insight knowledge of how a tool actually works and gets the data for us is always a plus.

We know validation is core of any forensics. One may use other tools and/or manually extract the data at byte level to validate the findings. This article exhibits how to go about parsing geo-tags of the images at byte level.

Collection of Geo-tag images

For the purpose of this experiment we took pictures from multiple devices such as

-          iPhone 3GS

-          iPod 4

-          Nessus 7

-          LG Optimus

-          HTC

We turned on the location service on every device in order to capture geo-tagged pictures.

It was interesting to note that in Nessus 7 did not have local camera application so the application ‘Cameringo’ was installed which has a feature to attach geo-tag in the pictures. Not all camera applications have this feature.

Geo-tag analysis of the images

-          Easiest and quickest way of checking geo location of a picture in Windows OS is to right click on the picture and select properties. Then under the detail tab, you will find the info.

-          One can also use tool to extract geo-tag and other metadata, for instance, exiftool is a free powerful tool.

-          One might have to validate or deal with cases where automatic recovery of geo-tag is not possible and manual parsing of raw image is required. This is what the article focuses on.

Manually parsing raw image

All devices that are used in this experiment found to have EXIF (Exchangeable Image File Format) standard of metadata logging.

Since the length and content of metadata (for example, make and model of camera, software, author, time etc.) vary from device to device, it is not surprising to see different starting offsets of geo-tag data. In other words, we could not find the consistency in the location offset of geo-tag in the image. But we did find a pattern to understand and get closer to the geo-tag offsets.

Scheme

We used following approach in our analysis.

1          Find the two direction letters i.e. N, S, E or W.

2         Then look proceeding offsets values for the pattern 00 00 xx xx  00 00 00 01 00 00 xx xx 00 00 00 01 a00 00 00 xx xx 00 00 64 or 00 00 03 E8. There is no predefined offset location to start with. The values are usually in big endian but we encountered a case involving little endian and reverse reading order.

3         Do your calculation and convert those values to something that makes sense.

Couple of things to keep in mind before jumping to calculation part are

-          Read set of 4 bytes for every value

-          The hex values given could be in big endian or little endian

-          00 00 00 64 = 100 decimal (Don’t convert it every time – a friendly advice J )

-          1 minute = 60 seconds

-          00 00 03 E8 = 1000 decimal

4         Use the direction letter for latitude and longitude respectively in order.

Proceeding sections demonstrate parsing of images from different sources.

Tools used

WinHex (any basic hex editor can be used)

Calculator (native application in Windows OS)

Image from iPhone

Offset          0    1    2   3   4    5   6   7    8    9  10 11 12 13 14 15

00001120   32 30 31 33 3A 30 35 3A  33 30 20 31 34 3A 30 39   2013:05:30 14:09

00001136   3A 31 39 00 32 30 31 33  3A 30 35 3A 33 30 20 31   :19 2013:05:30 1

00001152   34 3A 30 39 3A 31 39 00  00 00 31 8D 00 00 05 B1   4:09:19   1    ±

00001168   00 00 10 B9 00 00 05 A1  00 00 26 0D 00 00 05 26      ¹   ¡  &    &

00001184   00 00 00 4D 00 00 00 14  03 FF 02 FF 02 66 02 66      M     ÿ ÿ f f

00001200   00 0A 00 01 00 02 00 00  00 02 4E 00 00 00 00 02             N

00001216   00 05 00 00 00 03 00 00  02 CE 00 03 00 02 00 00            Î

00001232   00 02 57 00 00 00 00 04  00 05 00 00 00 03 00 00     W

00001248   02 E6 00 05 00 01 00 00  00 01 00 00 00 00 00 06    æ

00001264   00 05 00 00 00 01 00 00  02 FE 00 07 00 05 00 00            þ

00001280   00 03 00 00 03 06 00 10  00 02 00 00 00 02 54 00                 T

00001296   00 00 00 11 00 05 00 00  00 01 00 00 03 1E 00 1D

00001312   00 02 00 00 00 0B 00 00  03 26 00 00 00 00 00 00            &

00001328   00 1C 00 00 00 01 00 00  00 25 00 00 00 01 00 00            %

00001344   0B F4 00 00 00 64 00 00  00 51 00 00 00 01 00 00    ô   d   Q

00001360   00 17 00 00 00 01 00 00  15 53 00 00 00 64 00 00            S   d

00001376   34 E9 00 00 01 12 00 00  00 12 00 00 00 01 00 00   4é

00001392   00 09 00 00 00 01 00 00  00 13 00 00 00 01 00 04

00001408   1D 6F 00 00 03 74 32 30  31 33 3A 30 35 3A 33 30    o   t2013:05:30

00001424   00 00 FF E1 02 B0                                    ÿá °

Step 1

Scroll down till you find direction letter which is usually present near the date/time stamp. We found N and W.

Step 2

Look for the pattern 00 00 00 01 00 00 xx xx 00 00 00 01 … 00 00 00 64. Once the pattern is identified, find 4 bytes before the first set of 00 00 00 01 (highlighted with Turquoise) i.e. byte offset 1326 here.

Step 3

This is the most interesting step of calculation.

a)       Let’s start converting hex to dec from offset 1326.

00 00 00 1C => 28 and next 4 bytes are 00 00 00 01 => 1 (Divisor)

Thus the value of degree is 28/1 = 28.

Go to next 4 byte set whose value corresponds to 00 00 00 25 => 37, followed by another set of 00 00 00 01 => 1 (divisor). Thus 37/1 = 37 is the value of minutes.

Now calculating decimal value of seconds. Convert next 4 byte set 00 00 0B F4 => 3060. This set is followed by 00 00 00 64 => 100 (divisor). This time when you divide, you get, 3060/100 = 30.60 seconds.

This completes the latitude calculation which is 28:37:30.60

b)      We will continue, reading and converting the hex values for longitude and altitude.

00 00 00 51 => 81, next we have, 00 00 00 01 => 1. Degree is 81/1 = 81.

Then we have 00 00 00 17 => 23 and 00 00 00 01 => 1. Minutes comes out to be 23/1 = 23.

For seconds we have, 00 00 15 53 => 5459. Divisor is 00 00 00 64 => 100. Thus seconds is 5459/100 = 54.59.

Thus longitude is 81:23:54.59

c)       Similarly calculate altitude. The value we have in hex is 00 00 34 E9 => 13545. Divisor is 00 00 01 12 => 274. Altitude becomes 13545/274 = 49.4343

Step 4

Finally assigning the direction in order and co-relate the information from what properties is displaying in the below capture.

Latitude: 28:37:30.60 N

Longitude: 81:23:54.59 W

Altitude: 49.4343

iPhone

 

Image from iPod

Offset           0   1   2    3   4   5   6   7    8    9   10 11 12 13 14 15

00000512   00 00 00 05 32 30 31 33  3A 30 38 3A 32 32 20 31       2013:08:22 1

00000528   33 3A 32 37 3A 30 37 00  32 30 31 33 3A 30 38 3A   3:27:07 2013:08:

00000544   32 32 20 31 33 3A 32 37  3A 30 37 00 00 00 E0 FF   22 13:27:07   àÿ

00000560   00 00 30 FC 00 00 12 ED  00 00 07 7E 00 00 07 8E     0ü   í   ~   Ž

00000576   00 00 07 25 00 00 00 4D  00 00 00 14 00 07 00 01      %   M

00000592   00 02 00 00 00 02 4E 00  00 00 00 02 00 05 00 00         N

00000608   00 03 00 00 02 9A 00 03  00 02 00 00 00 02 57 00        š        W

00000624   00 00 00 04 00 05 00 00  00 03 00 00 02 B2 00 05                ²

00000640   00 01 00 00 00 01 00 00  00 00 00 06 00 05 00 00

00000656   00 01 00 00 02 CA 00 07  00 05 00 00 00 03 00 00        Ê

00000672   02 D2 00 00 00 00 00 00  00 1C 00 00 00 01 00 00    Ò

00000688   0D 90 00 00 00 64 00 00  00 00 00 00 00 01 00 00        d

00000704   00 51 00 00 00 01 00 00  04 D5 00 00 00 64 00 00    Q       Õ   d

00000720   00 00 00 00 00 01 00 00  38 FC 00 00 01 B5 00 00           8ü   µ

00000736   00 11 00 00 00 01 00 00  00 1A 00 00 00 01 00 00

00000752   13 3C 00 00 00 64 00 06  01 03 00 03 00 00 00 01    <   d

00000768   00 06 00 00 01 1A 00 05

Step 1

Look for direction letters (yellow highlighted).

Step 2

Identify the pattern (green highlighted).

Step 3

a)       Start with the set of 4 bytes, offset 678-681 (highlighted Turquoise).

00 00 00 1C => 28

Next 4 bytes 00 00 00 01 gives divisor, 28/1= 28 degrees

Count from offset 690-693, 00 00 0D 90 => 3472

Again the next 4 bytes gives divisor 00 00 00 64 => 100 and the value of minute will be 3472/100 = 34.72.

Note that we have minutes in decimal and we know that

I degree = 60 minutes

I minute = 60 seconds.

Therefore converting minutes to seconds as 0.72 * 60 = 43.2 seconds.

Since we have already calculated seconds by minutes here, next 8 bytes are of no use which is 00 00 00 00 00 00 00 01.

That completes our latitude calculation which is 28:34:43.2

b)      Moving forward to longitude bytes located at offset 702.

00 00 00 51 => 81 and 81/1 (next 4 bytes 00 00 00 01) = 81

Next, 00 00 04 D5 => 1237 and 1237/100 (next 4 bytes are 00 00 00 64) = 12.37.

Minutes = 12

Seconds = 0.37*60 = 22.2

Again, since the seconds has been calculated from the minutes, there is no separate 8 bytes for seconds calculation and you will see ‘00 00 00 00  00 00 00 01’ there.

Longitude is 81:12:22.2

c)       For altitude,

00 00 38 FC => 14588

Divisor is 00 00 01 B5 => 437

14588/437 = 33.38215

Step 4

Use the direction letters,

Latitude: 28:34:43.2 N

Longitude: 81:12:22.2 W

Altitude: 33.38215

Finally co-relating the findings from the one we get in picture properties.

iPod

 

Image from Nessus

Offset          0    1   2   3   4    5   6   7      8  9   10 11 12 13 14 15

00000144   00 00 32 30 31 33 3A 30  38 3A 32 32 20 31 33 3A     2013:08:22 13:

00000160   33 34 3A 30 36 00 43 61  6D 65 72 69 6E 67 6F 20   34:06 Cameringo

00000176   44 65 6D 6F 00 00 04 00  01 00 02 00 02 00 00 00   Demo

00000192   4E 00 00 00 04 00 05 00  03 00 00 00 E0 00 00 00   N           à

00000208   03 00 02 00 02 00 00 00  57 00 00 00 02 00 05 00           W

00000224   03 00 00 00 F8 00 00 00  00 00 00 00 51 00 00 00       ø       Q

00000240   01 00 00 00 0C 00 00 00  01 00 00 00 6C 54 00 00               lT

00000256   E8 03 00 00 1C 00 00 00  01 00 00 00 22 00 00 00   è           “

00000272   01 00 00 00 CA A0 00 00  E8 03 00 00 02 00 01 02       Ê   è

00000288   00 04 00 01 00 00 2E 01  00 00 02 02 04 00 01 00         .

00000304   00 00 00 00 00 00 00 00  00 00 FF                            ÿ

Step 1

Look for direction letters (yellow highlighted).

Step 2

Identify the pattern (green highlighted).

Step 3

Reading of bytes is totally reversed here. One may have to read backwards to get the latitude and longitude. In addition, the values are saved in little endian.

a)       Starting with offset 283 and going backwards. Thus from 283 – 280 (4 bytes) we have,

00 00 03 E8 (divisor) => 1000

From offset 279 – 276, 00 00 A0 CA => 41162

41162/1000 => 41.162 seconds

00 00 00 01 (divisor) = 1

00 00 00 22 => 34

34/1 = 34 minutes

Then we have 00 00 00 01 = 1

00 00 00 1C = 28

28/1 = 28 degrees

We got our latitude = 28:34:41.162

b)      Continue going backwards where we left from,

00 00 03 E8 => 1000

00 00 54 6C => 21612

21612/1000 = 21.612 seconds

Then 00 00 00 01 is the divisor

00 00 00 0C => 12

12/1 = minutes

Next we have 00 00 00 01 (divisor) and

00 00 00 51 => 81

81/1 = 81 degrees

Longitude becomes

81:12:21.612

Step 4

With direction,

Latitude: 28:34:41.162 N

Longitude: 81:12:21.612 W

Finally matching the extracted information with the one windows identified locally, as shown below.

Nessus

Image from LG

Offset          0    1   2   3    4   5   6   7    8   9   10 11 12 13 14 15

00001216   00 00 03 00 00 00 01 00  00 00 00 00 00 00 01 00

00001232   00 01 CC 00 00 00 64 00  00 03 E8 00 00 00 01 00     Ì   d   è

00001248   00 00 00 00 00 00 00 00  01 00 00 00 00 FF FF 00                ÿÿ

00001264   08 00 01 00 02 00 00 00  02 4E 00 00 00 00 02 00            N

00001280   05 00 00 00 03 00 00 06  5D 00 03 00 02 00 00 00           ]

00001296   02 57 00 00 00 00 04 00  05 00 00 00 03 00 00 06    W

00001312   75 00 05 00 01 00 00 00  01 00 00 00 00 00 06 00   u

00001328   05 00 00 00 01 00 00 06  8D 00 07 00 05 00 00 00

00001344   03 00 00 06 95 00 1D 00  02 00 00 00 0B 00 00 06       •

00001360   AD 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00   ­

00001376   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001392   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001408   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001424   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001440   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001456   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001472   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001488   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001504   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001520   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001536   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001552   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001568   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001584   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001600   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001616   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001632   00 00 00 00 00 00 00 00  00 00 00 00 1C 00 00 00

00001648   01 00 00 00 22 00 00 00  01 00 00 A2 21 00 00 03       ”      ¢!

00001664   E8 00 00 00 51 00 00 00  01 00 00 00 0C 00 00 00   è   Q

00001680   01 00 00 56 FE 00 00 03  E8 00 00 00 12 00 00 00      Vþ   è

00001696   01 00 00 00 11 00 00 00  01 00 00 00 17 00 00 00

00001712   01 00 00 00 18 00 00 00  01 32 30 31 33 3A 30 38            2013:08

00001728   3A 32 32 00 00 08 01 00  00 04 00 00 00 01 00 00   :22

00001744   00 A0 01 01 00 04 00 00  00 01 00 00 00 78 01 03                x

00001760   00 03 00 00 00 01 00 06  00 00 01 1A 00 05 00 00

00001776   00 01 00 00 08 3E 01 1B  00 05 00 00 00 01 00 00        >

00001792   08 46 01 28 00 03 00 00  00 01 00 02 00 00 02 01    F (

00001808   00 04 00 00 00 01 00 00  08 4E 02 02 00 04 00 00           N

00001824   00 01 00 00 13 A8 00 00  00 00 00 00 00 00 00 00        ¨

00001840   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

00001856   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00

Step 1

Look for direction letters (yellow highlighted).

Step 2

Identify the pattern (highlighted green). You must have noticed that in this case, we found the pattern quite farther from the direction letters (at offset 1640) unlike previous examples. 

Step 3

a)       00 00 00 1C => 28

00 00 00 01 => 1 (divisor)

28/1 = 28 degrees

00 00 00 22 => 34

00 00 00 01 = 1

34/1 = 34 minutes

00 00 A2 21 => 41505

00 00 03 E8 => 1000

41505/1000 = 41.505 seconds

Thus latitude is 28:34:41.505

b)      Continue reading hex,

00 00 00 51 => 81

00 00 00 01 => 1 (divisor)

81/1 = 81 degrees

Next 4 bytes are

00    00 00 0C => 12

00 00 00 01 => 1

12/1 = 12 minutes

00 00 56 FE => 22270

00 00 03 E8 => 1000

22270/1000 => 22.27 seconds

Thus longitude = 81:12:22.27

c)       Altitude is 18

Because,

00 00 00 12 => 18

00 00 00 01 => 1

18/1 = 18

Step 4

With direction,

Latitude: 28:34:41.505 N

Longitude: 81:12:22.27 W

Altitude: 18

Finally match the values to verify.

LG

Image from HTC phone

Offset           0   1   2   3    4   5    6   7    8   9   10 11 12 13 14 15

00004528   31 31 3A 30 34 3A 31 32  20 31 31 3A 30 37 3A 31   11:04:12 11:07:1

00004544   39 00 32 30 31 31 3A 30  34 3A 31 32 20 31 31 3A   9 2011:04:12 11:

00004560   30 37 3A 31 39 00 00 00  01 EC 00 00 00 64 00 01   07:19    ì   d

00004576   00 02 00 07 00 00 00 04  30 31 30 30 00 00 00 00           0100

00004592   00 00 00 00 00 0B 00 00  00 01 00 00 00 03 02 02

00004608   00 00 00 01 00 02 00 00  00 02 4E 00 00 00 00 02             N

00004624   00 05 00 00 00 03 00 00  12 72 00 03 00 02 00 00            r

00004640   00 02 57 00 00 00 00 04  00 05 00 00 00 03 00 00     W

00004656   12 8A 00 05 00 01 00 00  00 01 00 00 00 00 00 06    Š

00004672   00 05 00 00 00 01 00 00  12 A2 00 07 00 05 00 00            ¢

00004688   00 03 00 00 12 AA 00 12  00 02 00 00 00 07 00 00        ª

00004704   12 C2 00 1B 00 07 00 00  00 0F 00 00 12 CA 00 1D               Ê

00004720   00 02 00 00 00 0B 00 00  12 DA 00 00 00 00 00 00            Ú

00004736   00 26 00 00 00 01 00 00  00 2A 00 00 00 01 00 00    &       *

00004752   0A 45 00 00 00 64 00 00  00 4D 00 00 00 01 00 00    E   d   M

00004768   00 04 00 00 00 01 00 00  0D 7C 00 00 00 64 00 00            |   d

00004784   00 00 00 00 00 01 00 00  00 0F 00 00 00 01 00 00

00004800   00 07 00 00 00 01 00 00  00 13 00 00 00 01 57 47                 WG

00004816   53 2D 38 34 00 00 41 53  43 49 49 00 00 00 4E 45   S-84  ASCII   NE

00004832   54 57 4F 52 4B 00 32 30  31 31 3A 30 34 3A 31 32   TWORK 2011:04:12

00004848   00 00 00 00 00 06 01 03  00 03 00 00 00

Step 1

Look for direction letters (yellow highlighted).

Step 2

Identify the pattern (highlighted green).

Step 3

a)       For latitude

00 00 00 26 => 38

38/1 (divisor) = 38 degrees

00 00 00 2A => 42

42/1 = 42 minutes

00 00 0A 45 => 2629

2629/100 (divisor) = 26.29 seconds

Latitude is 38:42:26.29

b)      For longitude

00 00 00 4D => 77

77/1 = 77 degrees

00 00 00 04 => 4

4/1 = 4 minutes

00 00 0D 7C => 3452

3452/100 = 34.52 seconds.

Longitude is 77:4:34.52

Step 4

Match the calculated value with the one given by image properties.

HTC

 

References

http://en.wikipedia.org/wiki/Geotagging

About Nasa Quba & Kausar Khizra

Nasa Quba and Kausar Khizra graduated from University of Central Florida with MS degree in Digital Forensics. They are addicted to learn and work on diverse challenging projects and spread the knowledge to society.

Discussion

3 thoughts on “Geo-tag Forensics

  1. Hi guys,

    I notice you made no reference to the EXIF specification (http://www.exif.org/Exif2-2.PDF) even though all your images had metadata in EXIF form; was there a reason for this? By following it, it is quite possible to extract and parse the APP1 segment manually, and thus extract the GPS data, without needing a specific technique for each platform that an image may have originated from.

    Cheers.

    Posted by Adrian Wragg | September 9, 2013, 2:12 pm
  2. The blog post http://forensicsfromthesausagefactory.blogspot.co.uk/2013/03/location-data-within-jpgs.html documents recovery of location data from EXIF.

    Posted by Richard | October 1, 2013, 8:45 pm

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