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List:       ms-cryptoapi
Subject:    Re: CryptSignHash() reversed bytes
From:       Daniel Teng <daniel_teng_2000 () YAHOO ! COM>
Date:       2000-11-21 5:14:14
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Patrick,

I took a quick look at some previous postings and saw
that you had mentioned the bytes were in the wrong
order, although, at the time, I thought you meant
Big/little endian ordering and not actually the entire
byte stream.

Thanks again.
Daniel
--- Patrick Dolan <Patrick_Dolan@EFUNDS.COM> wrote:
> Daniel,
>
> The CryptoAPI's PKCS#1 bytes are in the wrong order,
> so you need to reverse
> them.  This probably occured due to Intel being a
> little endian machine.
> So I am not sure what the order would be on an Alpha
> chip!  Note, the
> CryptoAPI PKCS#7 signed messages are in the correct
> order, including the
> PKCS#1 blob contained within.
>
> Regards,
> Patrick.
>
>
>
>
>
> Daniel Teng
> <daniel_teng_2000@YAHOO.COM>@DISCUSS.MICROSOFT.COM>
> on
> 17/11/2000 05:33:03
>
> Please respond to Microsoft Cryptographic API
>       <CryptoAPI@DISCUSS.MICROSOFT.COM>
>
> Sent by:  Microsoft Cryptographic API
> <CryptoAPI@DISCUSS.MICROSOFT.COM>
>
>
> To:   CryptoAPI@DISCUSS.MICROSOFT.COM
> cc:
> Subject:  CryptSignHash() reversed bytes
>
>
> Hi,
>
> I encountered something a bit interesting with
> cryptsignhash and was wondering if it was
> intentional?
>
> I created a SHA-RSA signature with a Java Toolkit
> (IAIK from Austria).  This blob is a PKCS#1
> conformant
> blob.
>
> Then, I did the same thing under the CryptoApis:
> 1. put the same message ("Hello World") into a
> crypthash object,
> 2. computed the SHA hash
> 3. called cryptsignhash()
>
> At first, the results looked completely different.
> Then I realized that the bytes of the signature
> generated by cryptsignhash() were completely
> reversed
> from what I had generated from the Java side.  It
> was
> not just a byte ordering issue (big endian/little
> endian), the entire byte stream was reversed.
>
> I guess my question is...who is correct?  Is the
> Java
> output correctly structured as a PKCS#1 signature,
> or
> is the cryptoAPI output the correct format?
>
> I'm a bit concerned since I am currently generating
> signatures on a mixed set of client platforms, but
> verifying them all on the server side in Java.
>
> Thanks in advance.
>
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