Re: [Uta] Proposed definition of opportunistic encryption using TLS: draft-hoffman-uta-opportunistic-tls-00.txt

[Paul Hoffman <[e-mail]>]

On Feb 3, 2014, at 7:28 AM, Alan Johnston <[e-mail]> wrote:

> I'm less certain if the presence of a "transport=tls" parameter in the SIP message violates Paul's rule about not indicating that TLS has been used.

It does not violate the rule unless it is something that the user configures. If it is something set by the application developer (in this case, to follow the requirements of the protocol), but is not user-configurable, it's fine.

>  I'd need more explanation to understand this rule anyway, along with the rule that no user configuration be allowed. It is not clear to me how either of these does the harm that is described in the Security Considerations section.

Consider the HTTP / browser case. You have set up a TLS-accessible web site because security is good for the Internet, but you hate paying for and configuring a certificate for obvious reasons. If all common browsers let user say "always do TLS even for http: URLs, and ignore any server failure", you would configure your web server to do TLS with no certificate because that's good enough. That's a security reduction for the Internet.

> For VoIP and video calling in general, there is also the issue of encryption of the media - to use SRTP or use unencrypted RTP. For ZRTP, we developed an approach that could be considered opportunistic in this definition, although we described it "best effort encryption" (RFC 6189).  But that is a discussion for another thread!

Please, please note: "this definition" is only about TLS. I even called that out in the draft.

--Paul Hoffman