[dm-crypt] newbie qs on dm-crypt

Javier Juan Martínez Cabezón tazok.id0 at gmail.com
Tue Sep 11 21:06:09 CEST 2012


On 11/09/12 18:17, Anil wrote:
> Suppose I have a library of various crypto algorithms. It is proprietary.
> I build it as a module and want the user to run dm-crypt specifying my module to be run.
> For example,
> crypt FooCryptoLibrary-aes-xts
> I read that if your module is not GPL, then one cannot access core functions.
> Will there be a problem here?
> 
> 
> ________________________________
>  From: Arno Wagner <arno at wagner.name>
> To: dm-crypt at saout.de 
> Sent: Wednesday, September 5, 2012 7:41 AM
> Subject: Re: [dm-crypt] newbie qs on dm-crypt
>  
> On Tue, Sep 04, 2012 at 02:14:09PM -0700, Anil wrote:
>> Thanks for replying.
>> You said,
>> "Ciphers and modes are the job of the kernel, not dm-crypt."
> 
>>
>> I am trying to understand if?proprietary software can be used with
>> dm-crypt.
>>
> 
> That depends.
> 
>> I read it is in GPL mode. Which version? GPL v2, v3, LGPL...?
>>
>> For example, there is some in-house proprietary developed code for
>> AES-XTS.
>>
>> If I understood your reply correctly, then dm-crypt will call these
>> functions loaded into the kernel and there will not be any problem as the
>> GPL code (dm-crypt) will not be linked with the proprietary code.  Is that
>> so??
> 
> No. Kernels are different. If you do not distribute, it does not
> matter anyways. If you distribute, and want your stuff to stay 
> closed, you should probably talk to an IP lawyer. 
> 
> I have to say though that there is pobably no point, as AES-XTS is
> open and the kernel implementation is probably better than yours 
> anyways.
> 
> Arno
> 
> 
> 
>>
>>
>>
>> ________________________________
>>   From: Arno Wagner <arno at wagner.name>
>> To: dm-crypt at saout.de 
>> Sent: Monday, September 3, 2012 8:29 PM
>> Subject: Re: [dm-crypt] (no subject)
>>   
>> On Mon, Sep 03, 2012 at 06:20:35PM -0700, Anil wrote:
>>> Newbie here. I need to use dm-crypt with aes-xts. How is dm-crypt called? 
>>
>> Refer to the man-page and the FAQ. 
>>
>>> Is it possible to encrypt data while being saved on the fly?
>>
>> That is its job. It is not possible to do it in any other way.
>>
>>> Will there be file filters to encrypt/decrypt while saving 
>>> and opening the file?
>>
>> No.
>>
>>> Is aes-xts provided elsewhere as a plugin? or is it part of dmcrypt?
>>
>> Ciphers and modes are the job of the kernel, not dm-crypt.
>> It just uses them. 
>>
>> Arno
>> -- 
>> Arno Wagner,? ? Dr. sc. techn., Dipl. Inform.,?  Email: arno at wagner.name 
>> GnuPG:? ID: 1E25338F? FP: 0C30 5782 9D93 F785 E79C? 0296 797F 6B50 1E25 338F
>> ----
>> One of the painful things about our time is that those who feel certainty 
>> are stupid, and those with any imagination and understanding are filled 
>> with doubt and indecision. -- Bertrand Russell 
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> 
> 
> 
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If your module is not gpl I think you will not be able to use with
gpl-only-symbols unless you change this. However I think you shall do
this question in the kernel mailing list (dm-crypt is a userland tool).

I doubt if its legal that you modify a EXPORT_SYMBOL_GPL to a
EXPORT_SYMBOL one, for me is something like change the licence. I'm not
and expert is this question thought, but I think you shall ask this too
there.



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