Will, The encryption is just an additional capability you can have once you have a virtual partition. As for having ext2/3 FS on microSD, well, you can use many freeware addons for windows that can read it.
Or...use a Samba server on Android to access the partition as a "shared directory". This way internally you have a FS which supports all the permissions needed for isolation just as in internal memory, and a server which provides good interoperability between linux-like platform to a windows PC. The server gives another control mechanism for what you want to expose to the PC (which is even better than the current situation). If you want to read the MicroSD directly via a card reader - you will need the addon freewares (just google a bit). I hope that helps... Moses On Thu, Aug 6, 2009 at 2:44 AM, William Enck <[email protected]> wrote: > > Moses, > > I think my requirements were a little muddled when I was describing the > security mechanism I'm looking for. I'm not trying to create secure storage > on the SDcard. Rather, I'm looking for one file system that is accessed by > both Android applications and the PC, but still isolates Android > applications. That is, if AppA writes FileA, the default permissions keep > AppB from access it. However, when the phone is mounted on a PC, the user > can access FileA. > > Correct me if I'm wrong, but I don't think any of your solution provide > that functionality. > > Thanks, > > -Will > > Moses Roses wrote: > >> Hi, >> Basically is to create a partition which supports a stronger enabled FS. >> The 2 options I know of are : virtual disk via device mapper and real >> partition (FAT & EXT3) >> More elaboration on the methods: >> It is possible to have a virtual drive on the FAT, namely, you have one >> file on the FAT and that found is mounted (via device mapper) as a file >> system, meaning that you can have full yaffs2 or any other type of supported >> FS by the kerne. If you will use encrypted FS(dm-crypt), it will protected >> the visibility of file when mounted onto PC. >> You need to make sure that the kernel supports device mapper, and make >> sure that on the initial mounting table the new partition appears. >> A different method could be 2 partitions, one is FAT and the other any FS >> you want that the linux supports. For this method you can use simple tools >> such as gparted to do that. >> >> >> Good Luck, >> Moses >> On Mon, Aug 3, 2009 at 11:24 PM, William Enck <[email protected]<mailto: >> [email protected]>> wrote: >> >> >> Luis, >> >> You might look into a suitable way of securing data on the SDcard. >> It's a FAT file system, so you can't use UNIX permissions to >> restrict applications. Officially, nothing sensitive is supposed to >> be placed on the SDcard. However, there are some situations (at >> least in my research) where it would be nice to show through some >> sort of analysis that two applications truly are isolated and can't >> share data, even through the SDcard. >> >> The difficulty is that the SDcard needs to be FAT, because the PC >> mounts it. I read on one of the Android mailing lists a while back >> that there is a desire not to make kernel modifications to support >> such isolation. That may, or may not, be a requirement for you. >> >> This leaves the question of how to add security to the SDcard in >> such a way that it still allows the user to access all of the files >> when mounted on a PC. >> >> I've tried to get some Masters students here at Penn State to look >> at the problem, but no one bit (yet). It's not a particularly deep >> research problem, but it's something I'd like to see a good solution >> for. Part of your evaluation should look at how existing >> applications use the SDcard and whether or not your solution breaks >> these applications. Theoretically, Content Providers should be used, >> but this might not always be the case. >> >> Best, >> >> -Will >> >> >> Luis wrote: >> >> Hi all, >> >> I am looking to contribute to Android security and at the same time >> write my thesis. >> I have experience in C++ programming as well as other languages; >> and >> also in coporate security management. >> >> Any ideas of topics where I could help? >> >> Luis >> >> >>
