hackbod wrote: > (a) it uses a FAT > filesystem and... I'd just like to emphasise that if people write code that uses the SD card, this needs to be born in mind --- FAT has a few rather different semantics to a real Unix file system. Apart from the 2s-granularity timestamp, it also doesn't support sparse files.
I discovered this when I found that a simple call to RandomAccessFile.setLength() on FAT was taking 45 seconds to complete; rather than simply adjusting the length of the file as it does on yffs2, it was writing 15MB of zeroes to the card. [...] > Out of curiosity, are you interested in protecting your data from > access by the user, or malicious access from others? I don't know what his application is, but if it's anything like mine, we need to store secure hashes of data files to ensure that the user's not tampering with them. I know this is actually impossible to do, but we don't need perfect security, merely *good-enough* security; we want to make it sufficiently hard to produce fake hashes that most people won't bother, and in particular we'd need a scheme that ensured that if the security was broken on one device, it's not also broken on all other devices. For example, we could store an encrypted datafile with a key based on the application signature itself seeded with the device ID. Since the key can be calculated with code, it wouldn't be stored anywhere, so any attacker would have to extract the key from a running program (which is quite hard!); and even if someone did manage this and was able to decrypt the datafile, they'd need to repeat the process on every other phone. But as this is a lot of work, it'd be much more convenient if there was a proper secure datastore on the device. Unfortunately the concept of 'secure (from the user)' and 'open device' are probably antithetical... -- David Given [EMAIL PROTECTED] --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] Announcing the new M5 SDK! http://android-developers.blogspot.com/2008/02/android-sdk-m5-rc14-now-available.html For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -~----------~----~----~----~------~----~------~--~---
