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Cloud Computing and Mobile Devices

The explosive proliferation of mobile devices — smartphones, netbooks, and tablets — presents new challenges for software development. These devices have limited screen size, limited CPU and memory resources, and most importantly, limited power; these constraints will complicate the direct migration of existing thick client desktop software products to these devices. Computationally expensive applications will be very sensitive to these constraints, given that most devices employ CPU throttling to conserve power and to increase longevity for other functions, and CPU use on these devices will need to be minimized wherever possible.

Future advances in technology may alleviate some of these concerns, but battery technology has traditionally failed to keep pace with Moore’s Law, especially in cases of miniaturization, and thus the power concerns, and by extension the CPU concerns, may persist.

Cloud computing provides a potential solution for these concerns. In terms of power consumption, cloud computing provides a source of remote CPU cycles that do not consume device power, and these remote CPU cycles can be used to enable computationally expensive applications to operate on devices with a significantly lower net device power cost. Network power consumption will be marginally increased when using cloud-based resources, but the research hypothesis is that overall device power consumption will be significantly reduced.

I submit that a new application paradigm for these devices will need to evolve from the seeds of cloud computing, web applications, and client/server software in order to minimize device power consumption while otherwise providing a recognizable application user interface. The tools and infrastructure for these applications must be designed to maintain a bidirectional stream of data, visuals, and interface actions between a device and a cloud-based application provider, and to do so in a manner that will be both cost effective and beneficial for the power consumption of the device.

Tags: ipad, iphone

How to Jailbreak iPhone 3.01

Apple just released the iPhone 3.01 firmware update, and that means it is time to update my jailbroken iPhone to 3.01 and then jailbreak it again. In the past, I have been a happy user of PwnageTool for the jailbreak, and I would be again except that PwnageTool hasn’t been updated yet for the 3.01 firmware. Doh! I could just wait for the PwnageTool update, but the firmware update is to address a SMS crack that can give someone root on your phone. So I guess I better find a way to do this without PwnageTool.

After the requisite sync and aptbackup, I decided I would first try a quick hack and see how smart PwnageTool is. I put PwnageTool in expert mode and browsed to the 3.01 firmware IPSW to see if I could trick PwnageTool into building a custom IPSW from the 3.01 IPSW. No such luck — PwnageTool checks the firmware and simply won’t do it if it isn’t a supported IPSW version (and 3.01 is not supported in the current version of PwnageTool). So I guess I really do need to use something other than PwnageTool for the jailbreak.

Luckily, I found a post on the dev-team blog that says you can use redsn0w 0.8 to jailbreak the 3.01 firmware provided that you use the 3.0 IPSW as a base. Apparently the changes in 3.01 are very minimal and the redsn0w jailbreak procedure only changes a few things within the existing firmware, rather than completely overwriting it as PwnageTool seems to do. I couldn’t find any good postings with a complete set of instructions on how to do this with redsn0w, but here is what ultimately worked for me:

1. Connect your phone to iTunes and do a sync. Always good to start with this.
2. Run aptbackup and select “Backup” so we can restore Cydia after the upgrade and jailbreak.
3. In iTunes, restore your iPhone. This will also upgrade the firmware to the official 3.01 from Apple.
4. Run redsn0w 0.8, and select the 3.0 IPSW (iPhone1,2_3.0_7A341_Restore.ipsw) firmware from ~/Library/iTunes/iPhone Software Updates
5. Follow the instructions to put the phone in DFU mode. Note these are different than how PwnageTool does it, and you need to start with your phone off and connected to iTunes.
6. Once you are in DFU mode, kickoff the jailbreak.
7. At some point during the jailbreak, redsn0w told me it was waiting for a reboot. I waited quite a while, and it seemed to be hung. As a last resort, I decided to unplug the iPhone and start over. I unplugged the iPhone and plugged it back in, and…viola! The phone jumped into the redsn0w firmware loader screen and the jailbreak proceeded to completion. I don’t know if I was supposed to do this or not (like I said, I don’t normally use redsn0w)…but it worked.
8. After a little while my phone came back to life and rebooted and the jailbreak appeared to have succeeded, with Cydia installed.
9. Run aptbackup and select “Restore”. As part of the process, Cydia asked to upgrade a bunch of essential packages.
10. One more reboot to check everything and…all done. The firmware revision is now 3.01 according to iTunes, and I have all of my jailbroken applications restored and in place.

That’s it. I hope this helps. And I hope to see PwnageTool updated in the near future, since it has several features (like custom boot images) that I would like to use with my iPhone.

Tags: iphone