Thank you for the excellent advice! On 2010-09-20 18:09, Kevin Oberman wrote: > I recommend anyone attempting to secure their DNS read the NIST Computer > Security Resource Center document SP800-81 Rev.1, "Secure Domain Naming > System (DNS) Guide" at: > http://csrc.nist.gov/publications/nistpubs/800-81r1/sp-800-81r1.pdf > It recommends rolling th KSK every 12 to 24 months and the ZSK every 1 > to 3 months. These values are unchanged from the original SP800-81 > issues back at least two years ago and probably three. Everyone I have > spoken with who works with crypto feels that, barring a math > breakthough, these numbers are VERY conservative. Very interesting read.
However, for my original question, the NIST document says: > If the zone is signed using NSEC3 RRs, the salt value should be changed > every time the zone is completely resigned Since my zone is only updated dynamically, I'll never *completely* resign my zone... Also, they do mention that "[the salt] should be changed on a regular basis to maintain protection against zone enumeration." However, I don't see how it protects the zone from that if I use Daniel Bernstein's method (i.e. guess a name & hash it. If it's outside a known hash-range, request the server. Either it's a hit, or it's a new hash-range.) If the hash changes halfway through the procedure, I just rehash all my hits and go on. This is hardly a slowdown at all. >> Online/offline keys >> Sometimes this may be a choice, other times legislative or standards >> compliance will require certain behaviour. I've seen some documents require >> that even ZSKs remain offline (government agencies mostly), but generally >> its not considered much benefit if it rolls over reasonably often. KSKs are >> more commonly recommended to remain offline, but that definition can vary as >> well. A genuine HSM (Hardware Security Module), is not likely to be found in >> the bulk of DNSSEC deployments, due to cost, complexity and operational >> staff skills. Thus most operations will find it easier to generate keys >> either on the master server (perhaps the only server with key generating >> software) or close by (another server that is nevertheless "online"). If you >> don't use an offline HSM, then your alternatives will require you to have >> shorter roll over times in my opinion. > > HSMs are the way to go...if you can afford them. Prices vary a LOT from > expensive to WOW! (So does functionality, and DNSSEC will typically take > very little.) Because of dynamic DNS requirements, keeping the private > ZSK on-line is allowed, even for government sites, though ONLY in cases > where dynamic DNS is used or the back-end DNS management system requires > it. Government sites may not keep the KSK on-line. See SP800-81r1 > Section 9.4 for details. It's a private zone; HSM's are waaaaaay too expensive for that purpose! I use DDNS daily, so that requires the ZSK to be online. The KSK can remain offline if I manually resign the new DNSKEY RRset every Lzsk (i.e. every month). I'm not sure I'll have the courage to do this... _______________________________________________ bind-users mailing list firstname.lastname@example.org https://lists.isc.org/mailman/listinfo/bind-users