[149005] in cryptography@c2.net mail archive
Re: [Cryptography] Advances in homomorphic encryption
daemon@ATHENA.MIT.EDU (Christian Huitema)
Sun Jan 12 15:24:05 2014
X-Original-To: cryptography@metzdowd.com
From: "Christian Huitema" <huitema@huitema.net>
To: "'Bear'" <bear@sonic.net>
In-Reply-To: <1389547303.5172.207.camel@excessive.dsl.static.sonic.net>
Date: Sun, 12 Jan 2014 11:38:22 -0800
Cc: 'Eric Mill' <eric@konklone.com>, 'Jonathan Katz' <jkatz@cs.umd.edu>,
'Landon Hurley' <ljrhurley@gmail.com>, cryptography@metzdowd.com
Errors-To: cryptography-bounces+crypto.discuss=bloom-picayune.mit.edu@metzdowd.com
> Of course there are other possibilities like discrete integral fields
> for year, month, day, hour, minute, that could be checked quickly
> in succession -- first by stepping through years looking for equality,
> then months, then days, then hours, then minutes. You could figure
> out whether a particular transaction is within a given date range by
> making a relatively quick and simple series of equality checks.
I don't think you can do that if the encryption provides true semantic security. In van Dijk and Gentry's proposal, encryption of is achieved by mixing the original number with a random number r, so that the encryption depends on r but the decryption does not. This ensures that the same number can be encrypted in multiple different ways. It also precludes any simple comparisons, pretty much by design.
-- Christian Huitema
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