Locking individual files on micro sd card I have Galaxy S2 running on android 4.0.3. I have a number of photos, videos, pdf and word files stored on the micro sd card.

I am just wondering if there is a way to password protect individual files.

Many thanks
Short answer: 

Maybe.

Long answer: 

The SDCard is formatted with the legacy MSDOS FAT16 filesystem, which enables compatibility for the most part, largely majority with the Windows platform, not to mention Linux and others. It is for that reason, there is absolutely zero mechanism within that filesystem from a security standpoint. That is the trade-off with legacy filesystem and interchangeability with different desktop systems.

However, the alternative may be, is to format the SDCard to use one of the variety of Linux only filesystems where you can put permissions on each directory to prevent it from being browsable. Notably, ext3fs or ext4fs (Extended Filesystem 3rd and 4th edition respectively). That you might get away with but could induce side effects with the stock Android applications such as Gallery, Music Player. 

The one thing that springs to mind, albeit from a technical view-point, would be, to have a Android service running in the background that is monitoring file access to those files in question and the service could trigger a rudimentary dialog box prompting for the password based on the list of files the service can monitor based on your choosing.

A bit of quick google-fu yielded this hit on this app that might be the very thing you're looking for.


  With VeryAndroid File Protector, you can pick files and folders on
  your android phone or computer to protect with password.


Actually, that is what I have mentioned above! Well, reading the reviews, some disgruntled people felt they were cheated out of it, its free for 48 hours and having to pay a premium price - 19.95 accordingly to the review!