[guardian-dev] Sharing encrypted content with other apps

Nick Parker nparker at zetetic.net
Wed Jan 29 09:57:11 EST 2014

Hi Michael,

That is an interesting idea, SQLCipher supports in-memory databases via
the special filename :memory:, however accessing the raw representation
of the database becomes more challenging.  One approach that might be
considered is implementing and registering a custom in-memory virtual
file system.


On 1/28/14, 5:54 PM, Michael Rogers wrote:
> Hi all,
> I've been pondering whether it's possible for an Android app to share
> encrypted content - for example, an image stored in a SQLCipher
> database - with another app, without first creating an unencrypted
> copy of the content on disk.
> If we didn't mind creating an unencrypted copy of the content we could
> write it to a file, use a FileProvider to get a content URI for the
> file, and use an Intent to share the URI with the other app. Can that
> process be modified to avoid making a copy of the content?
> One possibility would be to create a named pipe with mkfifo(), use a
> FileProvider to create a content URI for the pipe, use an Intent to
> share the URI with the other app, and then stream the data from
> storage to the pipe.
> Another possibility would be to use ParcelFileDescriptor.createPipe()
> to create a pair of ParcelFileDescriptors, use an Intent to pass the
> read descriptor to the other app, and then stream the data from
> storage to the write descriptor. But I guess most apps will expect to
> obtain content from URIs rather than ParcelFileDescriptors.
> Has anyone on the list tried something like this? Any suggestions?
> Cheers,
> Michael
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Nick Parker

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