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Re: [TLS] Transcript-Hash during Handshake

"Le Van Gong, Hubert" <hubert@levangong.org> Wed, 22 November 2017 04:36 UTC

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To: Peter Wu <peter@lekensteyn.nl>
Cc: tls@ietf.org
References: <94ced158-63b1-e7a3-024c-44d1149e7202@levangong.org> <20171122035915.GD18321@al>
From: "Le Van Gong, Hubert" <hubert@levangong.org>
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Date: Tue, 21 Nov 2017 20:36:45 -0800
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Subject: Re: [TLS] Transcript-Hash during Handshake
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Hi Peter,

Yes, that sentence is what made me think it must be over decrypted messages but I wanted to double check as it's not clearly stated.
Thanks for confirming!

Hubert

On 11/21/17 19:59, Peter Wu wrote:

> Hi Hubert,
>
> On Tue, Nov 21, 2017 at 07:38:16PM -0800, Le Van Gong, Hubert wrote:
>> Greetings,
>>
>> Probably a trivial question but is the transcript hash (during handhsake)
>> calculated over decrypted versions of messages like EncryptedExtensions or
>> certificate or is it done over the raw/encrypted messages?
>> I could not find an exact confirmation in the spec.
> It covers the decrypted handshake messages, see
> https://tools.ietf.org/html/draft-ietf-tls-tls13-21#section-4.4.1
>
>      This value is computed by hashing the concatenation
>      of each included handshake message, including the handshake message
>      header carrying the handshake message type and length fields, but not
>      including record layer headers
>
> (The only way to know the message type is to have it in cleartext.)
>

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