On Mon, Oct 7, 2013 at 10:33 AM, Paul Wouters <[email protected]> wrote:

> On Thu, 3 Oct 2013, Douglas Otis wrote:
>
>  Several have expressed valid concerns regarding abuse of encrypted email.
>>
>
> One can always request encrypted email is signed. Than an abuser's key
> can simply be blacklisted. Or all encrypted but not signed email can be
> refused or disgarded. Encryption and key verification in DNS is actually
> a really good anti-spammer tool.


Note that this would require Encrypt-then-Sign or
Sign-then-Encrypt-then-Sign, either of which has some security implications.
<http://tools.ietf.org/html/rfc5751#section-3.6>

--Richard



>
>
>  That said, proprietary schemes are available permitting multiple decoding
>> keys derived from conveyed indexes.  The derived keys are
>> assigned to outbound message scanners used by enterprises to
>> ensure governmental data compliance requirements while also ensuring the
>> integrity of the entire path traversed.  If there is interest, I could
>> prevail on my employer to disclose IPR terms and details.
>>
>
> Generaly, I think people are only interested in hearing unencumbered
> ideas. So unless your employer has license terms that are unrestricted,
> I at least do not wish to hear it.
>
>
>  Secondly, while web based TLS exchanges normally ignore client
>> certificates, this would not be desirable for StartTLS related to open
>> email exchanges.  Currently, only source IP addresses are effectively
>> used to defend SMTP servers.
>>
>
> See above. If that is a concern, simply block encrypted but unsigned
> email. Or only allow signed email if the public key is available in DNS.
>
>
>  IPv6 will significantly challenge the use of source IP addresses.
>>
>
> Someone should tell Paul Vixie that, his ipv6 reverse check is
> preventing me from emailing him on various occasions when my mail
> client happens to get some v6 address :P
>
>
>  Secure SMTP using DNS-Based Authentication of Named Entities (DANE) TLSA
>> records and SMTP security via opportunistic DANE TLS offer
>> interesting starting points.  For this to work well, a more disruptive
>> approach is required where sending domains should be encouraged
>> to use their own certificates.  The initial availability of TSLA RRs
>> should not miss the opportunity to use this to signal a new
>> paradigm of expectations.
>>
>
> I am not sure what you are saying here?
>
> encryption is unrelated to authentication or authorization. spam and
> verifiable email origin are unrelated to encrypted the content (and/or
> meta data) of email. It just happens that we used to use the content
> and/or metadata to mark bogus email as spam. Clearly that has to change
> if we are successful at hiding those properties from passive attackers
> as well as anti-spam technologies.
>
> Paul
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