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Re: RevocationCodeIdentifier

From: Shivaram Mysore <shivarammysore@yahoo.com>
Date: Wed, 3 Nov 2004 10:34:57 -0800 (PST)
Message-ID: <20041103183457.967.qmail@web51509.mail.yahoo.com>
To: Tommy Lindberg <tommy.lindberg@gmail.com>
Cc: XKMS WG <www-xkms@w3.org>
Tommy,
 
Para [282]

<RevocationCodeIdentifier> [Optional] 
   Specifies a value to be used to validate a RevocationCode value in a subsequent Revocation request 
    

Section 7.1.2

[286]On initial registration the <RevocationCodeIdentifier> value is obtained by first performing the MAC calculation on the pass phrase value, then performing a second MAC calculation on the result.

[287]To prove knowledge of the pass phrase in a subsequent revocation request the <RevocationCode> value is obtained by performing the MAC calculation on the pass phrase value.

[288]The double MAC calculation ensures that the <RevocationCode> value may be sent as plaintext without the risk of disclosing a value which might have been used by the end-user as a password in another context. A second advantage of employing the double MAC calculation is that it ensures XKMS service does not place arbitrary constraints on the length of or character set in which the pass phrase is encoded.

But, as per [288], we don't specify double MACing in [287].  I believe this is an error.  And if there is double MACing, then the values for RevocationCode and RevocationCodeIdentifier must be the same.

Can you throw some light on how current implementation is done?

Thanks

/Shivaram


Tommy Lindberg <tommy.lindberg@gmail.com> wrote:

Hi Shivaram -

The RevocationCodeIdentifier is the second hash of some client chosen
quantity whereas the RevocationCode is the first hash of the same
quantity - this is done according to the Limited Use Shared Secret
algorithm.

So, yes they should in that sense match. However, they will not be identical.

They might be incorrectly calculated ofcourse. Let me know if you
think that is the case.

Regards
Tommy


On Wed, 3 Nov 2004 09:47:05 -0800 (PST), Shivaram Mysore
wrote:
> 
> Hi, 
> 
> Should n't the RevocationCodeIdentifier in para [243] (example) 
> 
> 5AEAai06hFJEkuqyDyqNh8k/u3M=
> 
> 
> be matched with the same in example para[261] ? 
> PHx8li2SUhrJv2e1DyeWbGbD6rs=
> 
> Spec:
> http://www.w3.org/2001/XKMS/Drafts/XKMS-PR-DRAFT/PR-DRAFT-xkms-part-1.html 
> 
> /Shivaram
> 
> 
> http://www.geocities.com/shivarammysore/
> 
> ________________________________
> Do you Yahoo!?
> Check out the new Yahoo! Front Page. www.yahoo.com> 
>



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Received on Wednesday, 3 November 2004 18:35:28 GMT

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