On 3/27/23, 9:08 PM, "dns-operations on behalf of Viktor Dukhovni" 
<dns-operations-boun...@dns-oarc.net on behalf of ietf-d...@dukhovni.org> wrote:
>    Perhaps, but until the mythical post-quantum DNSSEC is needed, online
>    signers will use ECDSA, for which denial of existence is already
>    sufficiently compact, even with 4 RRSIGs (SOA + 3 NSEC3).

Idle muttering (note, idle muttering) - if you are doing on-line signing, why 
stick with NSEC or NSEC3 for denial?  They were designed in an era when host 
security was so poor that having private key material on an internet-connected 
host was considered a very bad idea.

NSEC and NSEC3 work on the principle that "I don't know what the query asks in 
advance but I need to precompute something(*) to sign (where the private key 
is).  The approach is to reveal what I do have and let the requestor figure out 
that what they asked for isn't here."  That entire premise is blown away by 
on-line signing, calling into question all the energy we put into the size of 
the multi-NSEC(3) responses for negative answers and all the energy we put into 
mitigating zone walking.

(*) - prior to "Negative Caching of DNS Queries (DNS NCACHE)" [RFC 2308], a 
response with a return code of "Name Error" (that RFC defined the term 
NXDOMAIN) and 0 answer records, 0 authority records, and 0 additional records, 
was a legal way to indicate the queried name does not exist.  I.e., there was 
nothing (0 bytes) that a digital signature could cover.  The NSEC record (and 
then the NSE3) were created partly to have something to sign.

Sure, the cost of replacing NSEC and NSEC3 would be another resource record 
type code roll (such as 5->8, RSA-SHA1 vs RSA-SHA1-NSEC3).  But a new 
on-the-fly denial of existence might prove to be worth it in operations.


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