Re: [TLS] DSA should die

Watson Ladd <watsonbladd@gmail.com> Thu, 02 April 2015 05:32 UTC

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References: <201504012115.09048.davemgarrett@gmail.com> <20150402021723.AD9EC1B25A@ld9781.wdf.sap.corp>
Date: Wed, 1 Apr 2015 22:32:52 -0700
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From: Watson Ladd <watsonbladd@gmail.com>
To: "mrex@sap.com" <mrex@sap.com>
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Subject: Re: [TLS] DSA should die
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On Wed, Apr 1, 2015 at 7:17 PM, Martin Rex <mrex@sap.com> wrote:
> Dave Garrett wrote:
>> On Wednesday, April 01, 2015 08:40:40 pm Stephen Farrell wrote:
>>> <no-hats-except-the-330+-ciphersuites-is-crap-hat>
>>>
>>> Here's a suggestion: why pick 'em off one by one? How about
>>> creating a new registry that only includes stuff we think is
>>> really good for TLS1.3?
>>
>> I don't think a whole new registry is a good idea. The ClientHello
>> has to stay the same for backwards compatibility, and cipher suites
>> will need to be listed for TLS 1.2 compatibility at least.
>> Creating a whole new system is only good if you can completely
>> ignore the old one.
>>
>> There's plenty of space in the current registry if you want to
>> start over. Just say 0xD000 and up is for TLS2 suites, and all
>> below are TLS1. (at this point it's definitely time for 2.0)
>> Define TLS2 codepoints for valid combinations for TLS2 and the TLS1
>> would be invalid to negotiate for TLS2 but in there for TLS1.
>
> I agree that ClientHello needs to remain backwards-compatible.
>
> But how about using the Cipher Suites registry in a more creative fashion.
>
> For TLSv1.3, we could do the negotiation through he cipher suites list
> more like this:
>
>    0x10,0xXX    specifies a key exchange algorithm (XX) 256 codepoints
>    0x12,0xYY    specifies an authentication algorithm (YY) 256 codepoints
>    0x14,0xZZ    specifies a symmetric encryption scheme (ZZ) 256 codepoints
>    0x16,0xQQ    specifies a mac algorithm (QQ) 256 codepoints
>    0x18,0xPP    specifies a PRF algorithm (PP) 256 codepoints
>
> (with a little room in between if we ever exceed the 256 codepoints)

I don't understand why we want a different mechanism for TLS 1.3 and
TLS 1.2 ciphersuite negotiation. Even worse, I don't see how something
like SRP fits cleanly into the scheme above. Yes, SRP is little-used,
but people seem to think it's important.

What's wrong with the existing mechanism, if we remove things we don't want?

Sincerely,
Watson Ladd
>
>
> -Martin
>
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