1 Introduction
Small Scale Digital Devices (SSDD) can be seen as a subgroup of embedded systems. An embedded system is in general a small computer with a special purpose to perform one or a few dedicated functions, e.g., a controller. The system basically consists of a microprocessor, a non-volatile memory (mostly flash) and a volatile memory (RAM) and connectors and is usually embedded as part of a complete device. Additional parts can be added to the system by design or as required. Because the embedded system is adapted to its purpose, its size and costs can be reduced. An SSDD is such a device with several appropriate build-in attachments, e.g., a graphic or network controller. Harrill and Mislan covered the terminology SSDD in [HM07] and grouped them into five categories:
• Embedded Chip Devices,
• Personal Digital Assistants (PDAs),
• Cell Phones,
• Audio / Video Devices, and
• Gaming Devices.
With the size shrinking of transistors and other device parts either more and
more functionalities can be integrated into a predefined chip size or the device can be built smaller. As a consequence, many devices cannot be assigned to only one category, e.g., multimedia smart phones with built-in digital cameras.
Such systems find their way into our normal life, e.g., in form of cell phones, MP3 player, personal organizer, router, game consoles or modern network-capable TVs. SSDDs can be used to save several personal information like contacts, photos, calendar and notes. They started to displace classic paper helpers like schedules and address books. Therefore it can be supposed that SSDDs play an important role in forensics. An SSDD can also be a non-active device, like a USB (flash) drive, which must be considered in digital forensic analysis.
The statistics of the Federal Statistical Office of Germany from January 2007 [oG07] show that the distribution of SSDDs exceeds the distribution of PCs, see Table 1.1. That is why the necessity of forensic analysis of SSDDs increased in the last few years. Forensics on SSDDs is a very young field of science and although there is a great progress in developing analyzing tools and research, this field lags behind other forensic fields. Concurrently Anti-Forensics, the science of preventing forensic analysis, is more difficult because of the small size of the devices and the user’s restricted data accessibility [vdK07].
At the moment cell phones have the greatest distribution of all SSDDs. So it is no surprise that there exist a lot of public information on cell phone forensic.
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