On Friday, January 20, 2012 10:57:59 AM SM wrote:
> Hi Scott,
> 
> At 10:34 20-01-2012, Scott Kitterman wrote:
> >If this issue, AIUI, is that someone is worried that later this will be
> >referenced in an inappropriate way, I'm not sure what would satisfy that. 
> >I think it's already clear.
> 
> I don't think so.  One of the points mentioned by Murray [1] was:
> 
>    "the concern is that doing something like this on the standards
>     track might lead future efforts to believe this mechanism is
>     sufficient for arbitrary data protection when it is not."
> 
> One of the questions asked by the Responsible AD [2] was:
> 
>    "why there is any objection to doing HMAC (since it isn't hard to do)?"
> 
> The text from the DISCUSS is:
> 
>   "I don't think that's ok. I think you want HMAC() and not H().
> 
>    If I could supply a redactor with a zero length "private" string,
>    e.g. message with a header field like "To: @example.org" then the
>    redactor will send H(redaction-key) which can then allow (via
>    hash-continuation) checking if any value matches a value from an
>    output here.
> 
>    If the alphabet for sensitive values has N characters
>    then I can also send "To: "+char[i]+"@example.org" for
>    each i and then play the continuation game on that.
>    Same for two character prefixes etc.
> 
>   (2) I can also use this to validate guesses of the redaction
>   key value. I need to think about how one might avoid that
>   or if its possible to avoid that."
> 
> Regards,
> -sm
> 
> 1. http://www.ietf.org/mail-archive/web/marf/current/msg01681.html
> 2. http://www.ietf.org/mail-archive/web/marf/current/msg01691.html

Thanks for the clarification.

Scott K
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