[guardian-dev] IOCipher with ContentProvider openFile() Method

[Hans-Christoph Steiner]

Also, I looked at your updates to the ContentProvider question.  We
would love to make standard Android patterns work with as few changes as
possible.  Can you give us a working example of what you are trying to
do, without IOCipher, and we can use that to see how to fix IOCipher so
that it works in that situation.

.hc

On 09/21/2012 05:11 PM, Abel Luck wrote:
> Hey Aaron,
> 
> Thanks for the bug report :)
> 
> Each write call to libsqlfs (done by that Posix method pwriteBytes) has
> some significant SQL overhead. So, while I don't have the data to
> support it yet, my hypothesis is that the SQL overhead is causing poor
> performance.
> 
> Your workaround reduces the number of calls to libsqlfs, and hence the
> SQL overhead. We've talked about buffering small writes in IOCipher,
> then flushing them periodically in larger writes to libsqlfs, we'll see..
> 
> Another way to implement file copying is using FileChannels. The result
> is the same, a single large write is performed rather than a bunch of
> smaller writes.
> Here's an example snippet https://gist.github.com/3763841
> 
> We're still in the process of profiling and optimizing IOCipher and its
> underlying components. Your feedback is quite helpful, definitely keep
> it coming.
> 
> Soon, I hope to write some docs for IOCipher describing how using it
> differs from normal Java IO. Using larger buffers is a great example of
> the types of tips I hope to include there.
> 
> Cheers,
> 
> ~abel
> 
> Aaron Huttner:
>> Hey Abel,
>>
>> I saw you were the assignee on the Bug report so I thought I would update
>> you on a work around I'm trying out.
>>
>> I noticed (somewhat obviously) that the bigger I made the buffer the faster
>> it would copy the file. I'm not overly familiar w/ the intricacies of I/O,
>> let alone encrypted I/O, but it made sense that if the performance
>> increases with fewer writes I'd try to just do one big write. So I tried
>> copying the file to a ByteArrayOutputStream as an intermediary and then
>> just writing to the encrypted VFS in one call
>> (FileOutputStream.write(baos.toByteArray()). This significantly improved
>> write time to almost as quick as the native file system.
>>
>> This seems like a viable work around for me at the moment given the small
>> file sizes I'm dealing with. However, it's probably a bad idea for a
>> general work around.
>>
>> -Aaron
>>
>>
>>
>> On Fri, Sep 21, 2012 at 9:29 AM, Aaron Huttner <aaron at gryphn.co> wrote:
>>
>>> Thanks Hans,
>>>
>>> SQLCipher made a huge difference on our ability to get this app to the
>>> market as fast as we did and I'm really excited to use IOCipher to secure
>>> MMS attachments at rest. Honestly, it's like you guys are making exactly
>>> what we need when we need it.
>>>
>>> I'll definitely keep you posted, we've got some cool features/products in
>>> the pipe line.
>>>
>>> -Aaron
>>>
>>>
>>> On Thu, Sep 20, 2012 at 5:35 PM, Hans-Christoph Steiner <
>>> hans at guardianproject.info> wrote:
>>>
>>>>
>>>> I just looked into your company.  Sounds like you're making a nice,
>>>> tight Android app for secure messaging.  This is exactly the kind of
>>>> stuff we are aiming to support when we create dev tools like
>>>> SQLCipher-for-Android, IOCipher, Orlib, etc.  So please keep us posted
>>>> on how its working for you so we can incorporate your experience as we
>>>> push things further.
>>>>
>>>> We are also bringing on some more people so we should have more time
>>>> real soon to spend on improving IOCipher.
>>>>
>>>> .hc
>>>>
>>>> On 09/20/2012 04:45 PM, Aaron Huttner wrote:
>>>>> Reported, I'll keep that link bookmarked for the future.
>>>>>
>>>>> thanks.
>>>>>
>>>>> On Thu, Sep 20, 2012 at 4:33 PM, Nathan of Guardian <
>>>>> nathan at guardianproject.info> wrote:
>>>>>
>>>>>>  On 09/21/2012 02:01 AM, Aaron Huttner wrote:
>>>>>>
>>>>>> I'm not sure if you guys have a bug reporting email or not, my
>>>> apologies if
>>>>>> I missed it.
>>>>>>
>>>>>> Anyway, I think I found a bug in IOCipher where it takes forever (~2
>>>>>> minutes in reality) to copy a file from the SD card to the encrypted
>>>> VFS.
>>>>>> The same operation only takes about a second when I don't use IOCipher.
>>>>>> After performing a trace it's clear that the bulk of the time, ~99%, is
>>>>>> spent in the Posix.pwriteBytes() method of the IOCipher library. I've
>>>>>> attached a sample Android app (VfsTest.zip) and the trace file
>>>>>> (IOCipher.trace) to help illustrate the problem.
>>>>>>
>>>>>>  Thanks! You can report the bug here:
>>>>>>
>>>>>> https://dev.guardianproject.info/projects/iocipher/issues/new
>>>>>>
>>>>>> I have cc'd our core devs on the project.
>>>>>>
>>>>>> +n
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> Aaron Huttner, CTO
>>> Gryphn - "Mobile Privacy Simplified"
>>> +1-419-351-9133 | Aaron at gryphn.co
>>>
>>
>>
>>
> 
>