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Re: [TLS] Clarifications and questions: TLS1.3 - Static RSA and AEAD

"Blumenthal, Uri - 0558 - MITLL" <uri@ll.mit.edu> Tue, 27 May 2014 16:59 UTC

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From: "Blumenthal, Uri - 0558 - MITLL" <uri@ll.mit.edu>
To: Michael StJohns <msj@nthpermutation.com>, Eric Rescorla <ekr@rtfm.com>
Thread-Topic: [TLS] Clarifications and questions: TLS1.3 - Static RSA and AEAD
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Date: Tue, 27 May 2014 16:58:54 +0000
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Subject: Re: [TLS] Clarifications and questions: TLS1.3 - Static RSA and AEAD
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> You want cryptographic isolation between the key material produced from the
> master secret and the iv material produced from the IV, and the current spec
> doesn't do that.  See my last message to EKR.  One way to create this
> isolation is to derive the random IV data from a key that is different from
> the master secret - either a subkey derived from the master secret, or from a
> second key derived from the premaster.

You want the separation to be on a higher level.

I'd be happy with either one of the above.

>   A second way to create the isolation is to not generate the IV data from a
> key value and instead simply use an entropy expansion function on the
> client_random and server_random to generate the IVs.

Should be fine too, assuming at least one *_random is good enough.

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