Re: [AVTCORE] Kathleen Moriarty's No Objection on draft-ietf-avtcore-aria-srtp-10: (with COMMENT)

[Ben Campbell <[e-mail]>]

> On Aug 3, 2017, at 8:26 AM, Kathleen Moriarty <[e-mail]> wrote:
> 
> Hi Ben,
> 
> On Wed, Aug 2, 2017 at 11:15 PM, Ben Campbell <[e-mail]> wrote:
>> 
>>> On Aug 2, 2017, at 9:50 PM, Kathleen Moriarty <[e-mail]> wrote:
>>> 
>>> Hi Ben,
>>> 
>>> Thanks for the quick response, inline.
>>> 
>>> On Wed, Aug 2, 2017 at 10:36 PM, Ben Campbell <[e-mail]> wrote:
>>>> 
>>>> 
>>>> 
>>>>> On Aug 2, 2017, at 8:50 PM, Kathleen Moriarty <[e-mail]> wrote:
>>>>> ----------------------------------------------------------------------
>>>>> COMMENT:
>>>>> ----------------------------------------------------------------------
>>>>> 
>>>>> Although this is not a discuss, I think updated text would be very helpful on
>>>>> the following two issues.
>>>>> 
>>>>> I agree with the SecDir reviewer that there should be more text around the
>>>>> short tag length in the security considerations section.  I don't see a
>>>>> response to that post though.
>>>>> 
>>>> 
>>>> Hi Kathleen,
>>>> 
>>>> I think you are referring to Ben Laurie’s SecDir review of 06, rather than his later review of 09. Is that correct? Version 9 removed the GCM_8 modes. Or were you referring to something else?
>>> 
>>> I am referring to Ben's review of -06, where he had the following text:
>>> 
>>> Thirdly, I am not familiar enough with SRTP to understand why short
>>> authentication tags are needed, but in general its a bad idea, so I
>>> feel the Security Considerations should explain more fully than
>>> "Ciphersuites with short tag length may be
>>>  considered for specific application environments stated in 7.5 of
>>>  [RFC3711], but the risk of weak authentication described in
>>>  Section 9.5.1 of [RFC3711] should be taken into account."
>>> 
>>> I don't see an update to this text to address his question - providing
>>> additional information as to what should be "taken into account”.
>> 
>> I had assumed his concern was about short tags in GCM mode, namely the following:
>> 
>>       AEAD_ARIA_128_GCM_8
>>       AEAD_ARIA_256_GCM_8
>>       AEAD_ARIA_128_GCM_12
>>       AEAD_ARIA_256_GCM_12
>> 
>> These have all been removed as of version 09. Ben’s review of 09 made no further mention of short tags.
> 
> Thanks, but the text warning about them remains in the security
> considerations section.  Is it needed for some reason?
> 

Ah, I get it—I thought you were asking for _more_ text :-). I think they put that in as a result of the 06 review, but didn’t take it out when they removed those modes. I will verify that the authors don’t think the warning applies to any of the remaining.

Ben.

> Kathleen
> 
>> 
>> Are there suites still in version 09 that you think need further discussion in the security considerations?  I think the authors would happily add something if we can tell them what is needed, but I’m certainly not the expert here.
>> 
>> Ben.
>> 
> 
> 
> 
> -- 
> 
> Best regards,
> Kathleen