From: Ryan Sleevi [] 
Sent: Friday, March 2, 2018 11:22 AM
To: Phillip <>
Cc: CA/Browser Forum Public Discussion List <>; Paul Hoffman 
<>; Ben Wilson <>
Subject: Re: [cabfpub] [Ext] BR Authorized Ports, add 8443


More importantly though, how many validation approaches do we need? I would 
rather work on reducing them rather than increasing them further.


And 64KB should be enough for everybody, no one will need more than one 
monitor, XGA is plenty resolution, etc.


I would not obsess about the number of validation methods, I would rather us 
focus on ensuring a consistent level of assurance, and then work to help ensure 
that anyone and everyone on the Web can easily get a certificate and facilitate 
greater adoption of encryption.


Unlike 640K, a cryptographic digest is actually sufficient to authenticate any 
sequence of bits.


Since we require that any validation mechanism be described objectively, it 
follows that it can be described as a sequence of bits and thus that a 
cryptographic digest is sufficient.


So I am pretty sure that we can use a CAA record as the hook for pretty much 
any new validation mechanism we might propose. But as Ryan is pointing out, 
such mechanisms are not necessarily good ones or ones we should accept.



To be more precise in what was concerning me: I think that we should attempt to 
limit the number of Internet services, accounts, etc. that operators need to be 
concerned about restricting access to in order to prevent a malicious request 
for validation.


This is the concern that makes port 8443 unacceptable to me. Most of the 
billions of hosts on the net do not regard that port as privileged so we should 
not attempt to make it so. 


Rather than adding to the ports, accounts, etc. that we are requiring people to 
watch, I would like us to choose one affordance that has been created for the 
express purpose of being a gating point for issue. That is the CAA record.



If we need more flexibility in issue mechanisms, the most flexible approach I 
know of is to use a public key to validate the request. And I already use UDFs 
to authenticate public keys.


There clearly needs to be some part of any validation mechanism for a DNS based 
protocol that uses information that comes either directly or indirectly from 
the DNS system.

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