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RE: Secret Sharing
From: JAntonakos () excelsior edu
Date: Sat, 3 Aug 2013 16:42:44 -0400


Symmetric encryption uses a single key. Asymmetric encryption uses public
and private keys.

You encrypt with the public key and decrypt with the private key.

Best,
JLA



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-------- Original Message --------

From :      listbounce () securityfocus com
To :             saghar estehghari <s.estehghari () gmail com>
Cc :        webappsec () securityfocus com
Sent on : 08/01 12:01:34 PM EDT
Subject : Re: Secret Sharing

The answer is, I can't think of a better way of doing it. I believe
this is how EFS, etc. work - you have a single symmetric encryption
key and you encrypt this with the public key of anyone who you want to
be able to read the file.

But it's been a while since I read up on this, so I suggest you do a
sanity check.

cheers,
 Jamie

On 1 August 2013 15:48, saghar estehghari <s.estehghari () gmail com> wrote:
Hi,

I'm working on a project which involves security of the cloud data.

The scenario is as follows:

Users A and B have registered to a cloud service (cloud assumed to be
semi-trusted). A and B both have secret keys (KA and KB) (for
symmetric encryption) and public keys (PKA and PKB) on the cloud
server. KA and KB are each encrypted with the passwords of A and B.

Now consider A wants to share a file F that is encrypted with key K (K
is generate randomly by A). Now K should be shared securely with B
over the cloud (we consider that B is not online at the time of
sharing). To do this one option would be encrypting K with PKB which
should be decrypted by B when he gets online. However this option
seems to be complicated for my client.

I was wondering whether you have better options in mind that could help
me.
Please let me know if the explantation is not clear.

Thanks



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--
Jamie Riden / jamie () honeynet org / jamie.riden () gmail com
http://uk.linkedin.com/in/jamieriden



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