Re: HCRYPTKEY from actual key bytes
From: Levy (thebe14_at_gmail.com)
Date: 06/23/05
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Date: Thu, 23 Jun 2005 13:50:45 +0300
Ah, OK. Now I understand. My reading of the doc for CryptDecrypt was that on
the last block I can call it with less than a full block if I specify TRUE
for the bFinal parameter.
"lelteto" <lelteto@discussions.microsoft.com> wrote in message
news:E1FDB256-ABB8-40D4-84A3-53968166C0F6@microsoft.com...
> Yoy MUST send full blocks anyway so I don't understand your 'padding'
> issue
> at all. The encrypted content MUST always be multiple of full blocks.
> If your 'last chunk' is not full block than it surely cannot belong to an
> encrypted block. You would need somebody else's help (MS?) to figure out
> what's that last non-full-block chunk.
>
> Laszlo Elteto
> SafeNet, Inc.
>
> "Levy" wrote:
>
>> I am not sure I understand. I am decrypting the file's content by reading
>> in
>> blocks that are a multiple of the crypto algorithm's data block size,
>> then I
>> call CryptDecrypt with the final flag set to FALSE. The last data chunk
>> of
>> the file (which usually is larger than the data block size) is not a
>> multiple of the data block size. I was passing this last block to
>> CryptDecrypt, using TRUE for the bFinal flag. This last call fails.
>>
>> Now, are you saying that I also pass FALSE for the bFinal flag for this
>> last
>> block? But then, the data size of my last chunk should be a multiple of
>> the
>> algorithm's data block size (otherwise the operation fails, I think).
>> Should
>> I pad it? If yes, with what? And if I pad it, will it impact the
>> decryption
>> of the last few bytes of the file? I need to decrypt the entire file,
>> even
>> the last byte.
>>
>> Regards,
>> Levente
>
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