Palm OS Devices

Palm OS Devices

The Palm OS allows users to browse the wireless Web and the actual Web only in what it calls Web clipping, a browsing technique that strips graphics and complex functionality out of Web pages, leaving bare text to be displayed on a mobile device. Applications developed for Palm OS devices have become available in full force. They range from games, to office automation tools, to music players, to reference tools. The biggest advantage for Palm is its name brand recognition. Unfortunately, its production of new and exciting products has slowed as of late. Where Palm is slowing, other vendors are picking up the pace.

Two types of applications can be run on a Palm OS device: Web clipping applications (WCA) and regular GUI applications. On top of either of these, a conduit is sometimes necessary. A conduit is a tool used to synchronize data between a desktop application and a Palm OS device. WCAs are sets of HTML pages compressed into a proprietary format called a Palm Query Application (PQA) and downloaded to a device. Users input information to the HTML forms in these pages, and the WCA sends the request to the Palm.net proxy server. The Palm.net proxy server translates it into an HTTP request that is then forwarded to a company's Web server. That server is responsible for processing the information and returning the appropriate page. The returned page is relayed to the proxy server, compressed, and downloaded to the device. We are not sure of the degree of trust that should be afforded this proxy server, but applications developed in any environment should be constructed so that a compromise of sensitive data would not occur should the Palm.net proxy server be compromised.

WCAs are not standalone applications on a Palm OS device. They run inside a Palm OS application called the Web Clipping Application Viewer. The viewer is automatically launched when a WCA is invoked, or clicked by the user.

GUI applications that run on Palm OS devices are single-threaded and event-driven. Only one application can run at any given time. The OS automatically closes one application when another is invoked. Palm OS applications are compiled into Palm Resource Files (PRC files) and then downloaded to the handheld. The same PRC can run on any device licensed to run the Palm OS. Some of the devices have individual characteristics to which you can specifically program.

A few manufacturers license the Palm OS software and build devices around it. Palm's own devices, most recently the Palm VIIx, have only slightly different features from other vendors' devices powered by the Palm OS. Handspring, for instance, uses the Palm OS on its devices but adds functionality to attract portions of the market share. The most recent version of the Handspring products, the Visor Edge, has a 33MHz Motorola Dragonball processor. The Dragonball is the only processor that works with the Palm OS. It has 8MHz RAM and features the Palm OS 3.5.2H (not the most recent OS). The battery life on Palm OS devices is measured in weeks and varies, based on the screen brightness or applications run.

Input on typical Palm OS devices is accepted through a touch screen interface with a pen (called a stylus) used to touch options on the screen. Users can enter text either by selecting letter images on a keyboard on the screen or by writing Palm's signature, Graffiti language. Graffiti represents keystrokes used to write letters. The device recognizes keystroke patterns and displays the corresponding letters, numbers, or characters on the screen.

Network connectivity in Palm devices is offered in several forms. Connection via IrDA is integrated into the device. Serial or USB connections are possible via a cable by docking in a cradle. Connections are possible via a PC card or CompactFlash for 56Kbps modems and via PC cards, CompactFlash, or cradles for Ethernet. Springboard modules can provide connections to a cellular wide area network.

The Palm OS is logically similar to that of a traditional PC. At its base you find the device hardware and third-party hardware that can be added. Just above is the hardware abstraction layer, a software layout of how the hardware works. On top of this are the kernel and system services. The system services are a group of managers that give Palm OS its basic functionality:

         Graffiti manager

         Resource manager

         Feature manager

         Event manager

         Serial manager

         Sound manager

         Modem manager

Above these managers and system services are the system and third-party libraries. The system libraries include important components such as TCP/IP and floating-point support; they also allow developers to extend functionality of the OS. The third-party libraries can be communications-related or language-specific, such as Java libraries. Atop the libraries sits the application toolbox, and at the very top sit the device applications, such as the address book, mail functions, and calendar, as well as any third-party applications added to the device.

Palm Security

The last version of the Palm OS does encrypt passwords, but the encryption algorithm used has proven easily breakable. There is also a backdoor for the passwords, which can be easily used to circumvent the limited security a password provides. The backdoor is intentionally provided so that application developers can debug code. However, anyone performing source-level or assembly-level debugging can access information such as an encoded form of the system password and all information stored in the system database and can install or delete applications. The debugger is activated by using a short Graffiti keystroke pattern and is easily utilized.

As mentioned, according to Palm documentation, Palm OS 4.0 provides mitigation for this security problem. It also includes support for color displays and other supposed security enhancements. During 2001, Palm, Inc., announced its intention to spin off its OS department. The effect this spin-off will have on Palm OSs in general should prove interesting.

Palm OS data transfers are not encrypted by default. Additional applications can be used to introduce this functionality. Although some bolster the security offered, none provide an entirely robust security solution.

Palm OS 4.0

The newest version of Palm's operating system offers more expansion capabilities for secondary storage and has new APIs from the old versions. Palm OS 4.0 applications are copied into main RAM during execution and are removed automatically when terminated. Palm OS 4.0 supports multiple expansion cards in one device and extends the synchronizing API to provide access to expansion file systems. The install tool that comes with the OS supports non-Palm file types, enabling users to view different media types, such as music or graphic and picture files. A password is required to view details on event alarms, and the device can be automatically locked after a specified period of inactivity.

 



Wireless Security and Privacy(c) Best Practices and Design Techniques
Wireless Security and Privacy: Best Practices and Design Techniques
ISBN: 0201760347
EAN: 2147483647
Year: 2002
Pages: 73

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