Re: Encryption/Decryption

Tech-Archive recommends: Repair Windows Errors & Optimize Windows Performance

From: Don Dumitru [MSFT] (dondu_at_online.microsoft.com)
Date: 08/18/04 

Date: Tue, 17 Aug 2004 18:04:58 -0700

>From the thread going on in the microsoft.public.windowsce.embedded.vc
newsgroup, I am going to assume that this is getting resolved as an issue of
using an ANSI pass-phrase on the desktop, and a Unicode pass-phrase on the
device.

--Don 

-- 
This posting is provided "AS IS" with no warranties, and confers no rights.
"Don Dumitru [MSFT]" <dondu@online.microsoft.com> wrote in message 
news:OPB1KmLhEHA.904@TK2MSFTNGP09.phx.gbl...
> Can you provide the full URL for the sample, so I can be sure that we are 
> looking at exactly the same thing?  Without it, I don't know which actual 
> sample you might be looking at, and I can only guess at what problems you 
> are having, and I won'd be able to reliably reproduce the behavior myself.
>
> From your description, it sounds like the sample works by generating an 
> RC4 key into a key container for the user, and then encrypting / 
> decrypting the file using that key.  I am guessing here, but...  You run 
> an "init user" app on both the sender and the receiver, and give it the 
> same pass-phrase?  And it generates an RC4 key and places it in the user's 
> key container?  You then run an encryption program, which uses the stored 
> key to encrypt a file.  You move the file to the other machine, and run 
> the decryption program, which accesses the stored key and decrypts the 
> file.
>
> That's what it sounded like it was doing.
>
> The first thing to verify would be that you can decrypt the file 
> successfully, on the desktop, without Windows CE involved.  The next thing 
> to do is to build the "init user" app for Windows CE, and run it, and see 
> if it succeeds.  Ideally, you would single-step through with a debugger, 
> and examine each error return, in case the application itself does not 
> adequately report some error that it receives.  Finally, you need to build 
> the decryption program for Windows CE, run it, and again hopefully 
> single-step through it to examine error codes which might be getting 
> returned from various API's.
>
> From your description of how the app's are supposed to work, I would look 
> closely at how the "init user" and decryption programs access the RC4 key 
> stored in the key container.  Since Windows CE has a different user model 
> than the desktop, and since key containers are associated with users, this 
> is an area where the app could be getting different behavior than it was 
> expecting.  The most likely case is that some error is being returned, and 
> the app simply isn't checking the error code, and blindly cruising along 
> as if the API had succeeded.
>
> --Don
>
>
> "Arvind" <arvinds@erivasystems.com> wrote in message 
> news:%23yBu2MBhEHA.3964@TK2MSFTNGP12.phx.gbl...
>>i got it from www.msdn.com
>>
>> basically theres 2 applications..
>>
>> desktop for encrypting
>>
>> pocket pc for decrypting..
>>
>> ive used RC4 to encrypt and using the same to decrypt..
>> but im getting the wrong output file.
>>
>> i have used the inituser for client for storing and generating
>> keys(Container)
>>
>> but i couldnt find the same init user application for pocket pc
>>
>> can i get one?
>>
>> --
>> Thanks,
>>
>> Arvind
>>
>>
>> --
>> "eRiva Systems" - Where Technology Meets Life, Every Minute.
>>
>> arvindr@erivasystems.com
>>
>> www.erivasystems.com
>>
>> "Don Dumitru [MSFT]" <dondu@online.microsoft.com> wrote in message
>> news:#5ujxoYgEHA.1356@TK2MSFTNGP09.phx.gbl...
>>> Can you provide a URL for the sample which you used?  Was it a specific
>>> Windows CE sample, or a more general Win32 sample?  Presumably, some
>>> function call is failing, and the sample isn't reporting the failure.
>>>
>>> --Don
>>>
>>> --
>>> This posting is provided "AS IS" with no warranties, and confers no
>> rights.
>>>
>>>
>>> "Arvind" <arvinds@erivasystems.com> wrote in message
>>> news:u1BRZURgEHA.2764@TK2MSFTNGP11.phx.gbl...
>>> > Hello,
>>> >
>>> > im trying to use crypto API's in pocket pc (EVC++)
>>> >
>>> > to encrypt the WMV Files and decrypt the same.
>>> >
>>> > what i did is just copied the sample application which is provided in
>> the
>>> > help and tried to run in the pocket pc
>>> >
>>> > the application for encryption creates the destination file but the
>>> > content
>>> > are not added in that..
>>> > (File shows 0 BYTES)
>>> >
>>> > is there any other way around i have to try?
>>> >
>>> > plese let me know ur ideas..
>>> >
>>> > --
>>> > "eRiva Systems" - Where Technology Meets Life, Every Minute.
>>> >
>>> > arvindr@erivasystems.com
>>> >
>>> > www.erivasystems.com
>>> >
>>> >
>>>
>>>
>>
>>
>
>

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