Microsoft info-cards to use blind signatures?

[R.A. Hettinga]

<http://www.idcorner.org/index.php?p=88>

The Identity Corner
Stephan Brands

A corner on IDs
Postings on anything related to digital identity management.

3/30/2005

Microsoft info-cards to use blind signatures?
Posted by Stefan at 10:37 am

 Microsoft yesterday confirmed that it will provide info-card software into
Windows that will "put control of digital IDs into the hands of an
end-user" so that "the end-user will be in full control." Thus far, the
company has revealed no technical details about how info-cards will ensure
the privacy of certified identity assertions as they are being passed
around by their users. Now, I just learned that Microsoft last week has
been granted US patent no. 6,871,276 titled "Controlled-content recoverable
blinded certificates." Since I found out about this patent only half an
hour ago, I cannot yet comment on the novelty of the proposed solution,
other than that it seems to be a minor twist on Chaum's blind signature
patent that was filed in 1983. (The twist seems to be to use the
"decryption" exponent d to encode meaningful attribute information, a
technique that certainly has already been described by Chaum in various of
his post-1983 papers as well as patents; I need to review the entire patent
text first, however, before I can tell with certainty if there is a
significant and "technically non-obvious" difference in the proposed
encoding techniques.) Issues regarding patentability and technical
shortcomings notwithstanding, I am genuinely excited about this
development, if it can be taken as an indication that Microsoft is getting
serious about "privacy by design" for identity management. That is a big
"if," however: indeed, the same Microsoft researcher who came up with the
patent (hello Dan!) was also responsible for Microsoft e-cash patent no.
5,768,385 that was granted in 1998 but was never pursued. (See here for a
brief evaluation of the technical merits of that patent.) I am looking
forward to Microsoft coming forth with some technical details on
info-cards. Kim, can you share with us a few insights on the info-card
privacy design on your personal blog?


-- 
-----------------
R. A. Hettinga <mailto: rah at ibuc.com>
The Internet Bearer Underwriting Corporation <http://www.ibuc.com/>
44 Farquhar Street, Boston, MA 02131 USA
"... however it may deserve respect for its usefulness and antiquity,
[predicting the end of the world] has not been found agreeable to
experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'

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