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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 14:10 UTC

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From: "Blumenthal, Uri - 0558 - MITLL" <uri@ll.mit.edu>
To: "tls@ietf.org" <tls@ietf.org>
Thread-Topic: [TLS] Clarifications and questions: TLS1.3 - Static RSA and AEAD
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Date: Tue, 27 May 2014 14:09:55 +0000
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Archived-At: http://mailarchive.ietf.org/arch/msg/tls/fHn4FeyOPZv6moVYRzxcEDMT2fw
Subject: Re: [TLS] Clarifications and questions: TLS1.3 - Static RSA and AEAD
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>>>What would be the consequences of [removing key transport] for embedded
>>>servers that
>>> may not have a good source of randomness to meaningfully engage in
>>> [EC]DH[E]?
>>
>>
>> They will be in trouble. However, presumably if they have a place to
>>store
>> their private key, they can somehow store other random data there that
>> they use to generate random values, no?
>
>But then they can store an incrementing counter for use with AES with
>a fixed key as a RNG. I don't see the problem here.

Yes, that is definitely an option (why didn't I think of it myself?) - a
reasonably good PRNG for a source of randomness.

However I still am uneasy about the client being unable to tell the server
"This is *my* transaction, and I want you to use this key with this cipher
suite to protect it".

[I understand the value of PFS. :-]

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