Re: Same Inputs, different output = No searching

From: Daniel Sie [MSFT] (dsie_at_online.microsoft.com)
Date: 10/12/04 

Date: Mon, 11 Oct 2004 20:01:47 -0700

You can decrypt the copy in DB and then compare, but this probably will be
costly for the decryption operation. Another solution is to use an index
table using the hash as lookup. This way you can have fast lookup, and be
able to decrypt per your requirement. 

-- 
Thanks,
Daniel Sie [MSFT]
This posting is provided "AS IS" with no warranties, and confers no rights.
"D Barry" <google@dcbarry.com> wrote in message 
news:6d9b9a07.0410071227.353dfb4@posting.google.com...
> Help!
>
> Getting my first taste of crypto and CAPICOM. Didn't learn until
> testing that when encypting a value CAPICOM (regardeless of the
> algorithim chosen), there is an element of randomness applied so that
> even with the same inputs (plaintext and secret key), the output
> varies.  I understand why that is valuable (same idea as salting a
> hash), but it was a suprise to me.
>
> My problem is that I am storing SSNs (Socal Security Numbers) as part
> of customer info.  I don't (can't)  to store the SSN plaintext in the
> database, but I do want to be able to search on it for reverse
> lookups.  No problem, thinks I, just ask the user for the search value
> (SSN), encrypt that, and search on that value.     (In otherwords,
> I'll allow you to search by SSN, but I'm not going to (normally) allow
> you to see that value).
>
> Well, the entropy in CAPICOM effectively blows that idea away.  Or
> does it?  I really don't want to roll my own encryption here.
>
> Are there delivered MS solutions / algorithims where  plaintext +
> secret always equals the same encrypted value.  (I can't use secret
> keys that are unique to the machines -- I need to be able to define
> them myself.)
>
>
> Thanks,
>
> David
>

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