[cabfpub] Draft Ballot 185 - Limiting the Lifetime of Certificates: User input

Ryan Sleevi sleevi at google.com
Fri Feb 10 17:45:37 UTC 2017

On Fri, Feb 10, 2017 at 9:39 AM, philliph at comodo.com <philliph at comodo.com>

> I fail to see how this example shows a security improvement from reducing
> certificate validity.
> In the case that CABForum declares that certs of a particular type are to
> be decorated with attribute X, there will naturally have to be a phase in
> period. The normal practice for such a phase in would be to grandfather all
> the existing CAs for the period of the phase in and require new entrants to
> start using the new decoration immediately. So the only practical impact of
> the phase in period is that clients would have to carry both sets of code
> for the duration of the phase in. If the period is three years instead of
> one, they have to carry the legacy grandfather code for 24 extra months.
> That is an argument but it is not a security justification for the
> proposed change.

Given that multiple examples were provided, perhaps you might respond
specifically to each, rather than the ambiguity as to "this example"

For example, we know the EKUs are relevant, with respect to CA members
ambiguity with respect to what the "Scope of the Baseline Requirements"
are, as well as the prohibitions of certain practices for certificates "in
scope". So concretely, the introduction of an EKU defines the scope, and
thus provides a technical control to identify and reject things which the
CA might have interpreted as "out of scope", thereby protecting users.

Similarly, you've failed to address the matter of domain validation. Do you
believe these methods do not improve security at all? Given Comodo's
involvement and attention to them, I think that would be a fairly
surprising statement for many in this Forum to hear that Comodo does not
believe Ballot 169 improves the security through better domain controls.
Even more surprising would be if "this argument" referred to CAA, given
Comodo's responsibility in providing that draft. Does Comodo believe your
specification does not improve the security of the ecosystem, particularly
for Subscribers?
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