To create an MD5 / SHA1 file for a file, you need to access the file. At this point, extensions for most browsers are similar to pre-web applications. Native system support is not available for security extensions. The file system API ( http://www.w3.org/TR/FileAPI/ ) is not available or is available only for experimentation.
Check the following:
fooobar.com/questions/70243/...
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