Re: [ietf-dkim] r= for instilling good domain-name practices

On May 1, 2006, at 5:08 PM, Mark Delany wrote:
> Colo[u]r me confused, but I don't see what this has to do with the  
> base function of a domain claiming responsibility.
While the signer may be expected to react in cases of abuse, the base  
DKIM signature mechanism does not safely impart trust above the least  
trustworthy source being signed by the domain.  It remains doubtful  
how effective a reaction to abuse will be, for that matter.  Whether  
for messages from financial institutions or an ISPs, additional  
protection is required to both protect and retain the recipient's  
trust of messages being signed by a domain.  The DKIM signature  
should not be considered to provide a good reactive mechanism, but it  
can be a good proactive mechanism.

> Is this r= thing fundamental to that function or could it be  
> developed as a separate exercise above and beyond the base?
A wait in establishing a means to protect trust (based upon message  
annotation or filtering) may invoke a reaction to this limitation  
that could prove highly counter-productive.  The need for the added  
protection related to trust easily exceeds that of the x= parameter,  
in comparison.  Without a means to segregate sources of differing  
levels of trust or vetting, the only remaining alternative would be  
to utilize additional domain-names.  A reaction, due to this  
protective oversight, may produce a plethora of similar domain- 
names.  These additional domain names may actually result in phishing  
being even more lucrative, rather than being abated by the DKIM  
signature. : (
> After all, the whole point of the tag=value syntax is so that  
> additional functionality can be seamlessly added on.
The r= parameter, as just described, can be incorporated as an option  
when needed, in the same manner as the x= parameter.  For many, the  
additional annotation may not be needed.  In critical cases however,  
this r= annotation may prove vital at preventing rather dangerous  
exploits, and rather bad practices.  The real value of DKIM is found  
proactively establishing trust for selected messages from trusted  
domains.  In many, if not most cases, trust is better assured by  
offering an assured means to select messages.  It remains doubtful  
such selection can be achieved through the recognition of email- 
addresses.

> If r= is non-essential, then can we leave those discussions until  
> after the base work is done, otherwise it's just hindering us.
A good point.  There is no desire to hinder progress for non-critical  
concerns.  The r= parameter, or something similar, should be provided  
at the outset to avoid the proliferation of "segregated" domain  
names, a critical concern.  While companies such as yahoo have dealt  
with the problem of diminished trust of their well-known domain name  
by employing additional domain names, such as yahoo-inc, this  
strategy should be viewed as a bad practice when abating a phish  
threat.  The r= parameter provides an alternative to the use of  
different domain names when segregating sources.  Hopefully  
describing just three levels low (as a warning), normal, and high (as  
an assurance) is something easily understood and yet still provides a  
feasible alternative to segregating domains.
-Doug

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