Individual O. Kolkman
Internet-Draft RIPE NCC
Expires: February 19, 2004 R. Gieben
NLnet Labs
August 21, 2003
DNSSEC key operations
draft-kolkman-dnssec-operational-practices-00.txt
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This Internet-Draft is intended as a place holder for considerations
and operational practices for DNSSEC key-management. It is intended
to be 'long-lived' and result in documentation of best(?) current
practices.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Time in DNSSEC . . . . . . . . . . . . . . . . . . . . . . . 3
2.1 Time definitions . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Time considerations . . . . . . . . . . . . . . . . . . . . 4
3. Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1 Using Key-Signing and Zone-Signing Keys. . . . . . . . . . . 6
3.1.1 Motivations for the KSK and ZSK functions . . . . . . . . . 6
3.2 Key security considerations . . . . . . . . . . . . . . . . 6
3.3 Key rollovers . . . . . . . . . . . . . . . . . . . . . . . 7
3.3.1 Zone-signing key rollovers . . . . . . . . . . . . . . . . . 7
3.3.2 Key-signing key rollovers . . . . . . . . . . . . . . . . . 10
4. Planning for emergency key rollover. . . . . . . . . . . . . 11
4.1 KSK compromise . . . . . . . . . . . . . . . . . . . . . . . 12
4.2 ZSK compromise . . . . . . . . . . . . . . . . . . . . . . . 12
4.3 Compromises of keys configured at the resolver level . . . . 12
5. Parental policies. . . . . . . . . . . . . . . . . . . . . . 13
6. Initial key exchanges and parental policies
considerations. . . . . . . . . . . . . . . . . . . . . . . 13
6.1 Storing keys so hashes can be regenerated . . . . . . . . . 13
6.2 Self signed keys during upload or not? . . . . . . . . . . . 13
6.3 Security lameness checks. . . . . . . . . . . . . . . . . . 13
6.4 SIG DS validity period. . . . . . . . . . . . . . . . . . . 13
7. Resolver key configuration. . . . . . . . . . . . . . . . . 13
8. Security considerations . . . . . . . . . . . . . . . . . . 13
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 13
Normative References . . . . . . . . . . . . . . . . . . . . 14
Informative References . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 15
A. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 15
B. Zone-signing key rollover howto . . . . . . . . . . . . . . 16
C. Typographic conventions . . . . . . . . . . . . . . . . . . 16
Intellectual Property and Copyright Statements . . . . . . . 19
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1. Introduction
During workshops and early operational deployment test, operators and
system administrators have gained knowledge about operating DNSSEC
aware DNS services. This document intends to document the current
practices and the background on why practices are as they are.
The structure of the document is roughly as follows. We start with
discussing some of the consideration with respect to timing
parameters of DNS in relation to DNSSEC in Section 2. Aspects of Key
management such as key rollover schemes are described Section 3.
Emergency rollover considerations are addressed in Section 4. The
Typographic conventions used in this document are explained in
Appendix C
Since this is a document with operational suggestions and there is no
protocol specifications the RFC2119 [5] language does not apply.
2. Time in DNSSEC
In pre-DNSSEC DNS all times were relative. The SOA, refresh, retry
and expiration timers are counters that are being used to determine
the time since the most recent time a slave server synced (or tried
to sync) with a master server. The TTL value and the SOA minimum TTL
parameter [6] are used to to determine how long a forwarder should
cache data after it has been fetched from an authoritative server.
DNSSEC introduces an absolute time in the DNS. Signatures in DNSSEC
have an expiration date after which the signature is invalid and the
signed data is to be considered bad.
2.1 Time definitions
In this section we will be using a number of time related terms.
Within the context of this document the following definitions apply:
o "Signature validity period"
The period that a signature is valid. It starts at the time
specified in the signature inception field of the SIG RR and
ends at the time specified in the expiration field of the SIG
RR.
o "Signature refresh period"
Time after which a signature made with a key is replaced with a
new signature made with the same key. This replacement takes
place in the master zone file. If a signature is created on
time T0 and a new signature is made on time T1, the signature
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refresh time is T1 - T0. If all signatures are refreshed at
zone signing than the signature refresh period is equal to the
period between two consecutive zone signing operations.
o "Key usage period"
The period between when data signed with this key first appears
in the DNS and the time the authentication chain to this key is
broken i.e. the signature over the parental DS RR has expired
and this public key is not hard-configured as trusted entry
point into verifying resolvers. The "Key usage period" is
essentially the window of opportunity for cryptanalists to
attack a key.
o "Key publication period"
The period for which the public part of the key is published in
the DNS. The public part of the key can be published in the
DNS while it has not yet been used to sign data As soon as a
public key is published a brute force attack can be attempted
to recover the private key. Publishing the public key in
advance (and not signing any data with it) does not guard
against this attack.
o "Maximum/Minimum Zone TTL"
The maximum or minimum value of all the TTLs in your zone.
2.2 Time considerations
Because of the expiration of signatures one should consider the
following.
o The Maximum zone TTL of your zone data should be a fraction of
your signature validity period.
If the the TTL would be of similar order as the signature
validity period then all RRsets fetched during the validity
period would be cached until the signature expiration time.
The result would be that query behavior may become bursty.
We suggest the TTL on all the RRs in your zone to be at least
an order of magnitude smaller than your signature validity
period.
o The Minimum zone TTL should be long enough to fetch and verify all
the RRs in the authentication chain.
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1. During validation, some data may expire before
validation is complete. The validator should be able to
keep all the data, until validation is complete. This
applies to all data in the chain of trust: DSs, DNSKEYs,
RRSIGs, and the final answers i.e. the RR that is returned
for the initial query.
2. Frequent re-verification causes load on recursive
nameserver. Data at delegation points, DS, DNSKEY and
RRSIGs over that those should benefit from caching. The TTL
on those should be relatively long.
We have seen events where data needed for verification of an
authentication chain had expired from caches.
We suggest the TTL on DNSKEY and DSs to be at least of the
order 10 minutes to an hour and all the other RRs in your zone
to be at least 30 seconds. [Editors note: These are initial
values]
o The signature refresh period should at least be one maximum TTL
smaller than the signature validity period.
If a zone is resigned shortly before the end of the signature
validity period then this may cause simultaneous expire of data
from caches which leads to bursty query behavior and increase
the load on authoritative servers.
o Slave servers will need to be able to fetch newly signed zones
well before the data expires from your zone.
If a properly implemented slave server is not able to contact a
master server for an extended period it will at some point
expire and not hand out any data. If the server serves a
DNSSEC zone than it may well happen that the signatures expire
well before the SOA expiration timer counted down to zero. It
is not possible to fully prevent this from happening by
tweaking the SOA parameters. But the effects can be minimized
if the SOA expiration time is a fraction of the signature
validity period.
When a zone cannot be updated while signatures in that zone
have expired non-secure resolvers will continue to be able to
resolve the data served by the particular slave servers. Only
security aware resolvers that receive data with expired
signatures will experience problems.
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We suggest the SOA expiration timer being approximately one
third or one forth of the signature validity period.
We also suggest that operators of nameservers with slave zones
develop watchdogs to be able to spot these upcoming signature
expirations in slave zones, so that appropriate action can be
taken.
o [Editor's Note: Need examples here]
3. Keys
3.1 Using Key-Signing and Zone-Signing Keys.
3.1.1 Motivations for the KSK and ZSK functions
Although all data in a zone can simply be signed by one single key
using two keys has its advantages. Delegation Signer [7] introduced
the concept of key-signing and zone-signing keys while
Key-signing-flag [4] introduced the concept of a key with the Secure
Entry Point flag set; a key that is the first key from the zone when
following an authentication chain. When using a key-signing key with
the SEP flag set, where the parent has a DS RR pointing to that
DNSKEY, and when using zone-signing keys without the SEP flag set
one can use the following operational procedures.
The zone-signing key can be used to sign all the data in a zone on a
regular basis. When a zone-signing key is to be rolled over no
interactions with third parties are needed. This allows for
relatively short "Signature Validity Periods" (order of days).
The key-signing key (with the SEP flag set) is only to be used to
sign the Key RR set from the zone apex. If a key-signing key is to
be rolled over, there will be interactions with parties other than
the zone maintainer such as the registry of the parent zone or
administrators of verifying resolvers that have the particular key
configured as trusted entry points. Hence, the "Key Usage Time" of
these keys can and should be made much longer. Although, given a
long enough key, the "Key Usage Time" can be on the order of years we
suggest to plan for a "Key Usage Time" of the order of a few months
so that a key rollover remains an operational routine.
3.2 Key security considerations
In RFC2541 [2] a number of considerations with respect to the
security of keys are described. That document deals in detail with
generation, lifetime, size and storage of private keys.
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In Section 3 of RFC2541 [2], Eastlake does make some hard number
suggestions: 13 months for long-lived keys and 36 days for
transaction keys but suggestions for key lengths are not made.
[Editors note: We consider keylength suggestions outside of scope for
this document. Wess Griffin suggested: Hilarie Orman wrote a draft
(orman-public-key-lengths-05, it has expired) that had some good
discussion of public key lengths and matching them to symmetric
cipher key length strengths. Also there's eastlake-randomness2-04
that will obsolete RFC1750 that has an appendix on symmetric key
lengths. Not really applicable here, but a good discussion of how to
choose key lengths.]
3.3 Key rollovers
Key rollovers are a fact of live when using DNSSEC. A DNSSEC key
cannot be used eternally (see RFC2541 [2] and Section 3.2 ). Zone
maintainers who are in the process of rolling their keys have to take
into account that data they have published in previous versions of
their zone still lives in caches. When deploying DNSSEC this becomes
an important consideration; ignoring data that may be in caches may
lead to loss of service for clients
The most pressing example of this is when zone material which is
signed with an old key is being validated by a resolver who does not
have the old zone key cached. If the old key is no longer present in
the current zone, this validation fails, marking the data bad.
Alternatively, an attempt could be made to validate data which is
signed with a new key against a old key that lives a a local cache,
also resulting in data being marked bad.
To appreciate the situation one could think of a number of
authoritative servers that may not be instantaneously running the
same version of a zone and a security aware non-recursive resolver
that sits behind security aware caching forwarders.
[Editors note: This needs more verbose explanation, nobody will
appreciate the situation just yet. Help with text and examples will
be appreciated]
3.3.1 Zone-signing key rollovers
For zone-signing key rollovers there are two ways to make sure that
during the rollover the data still in caches can be verified with the
new keysets or the newly generated signatures can be verified with
the keys still in caches. One schema uses double signatures, it is
described in Section 3.3.1.1, the other uses key pre-publication
(Section 3.3.1.2). The pros and cons and recomendations are
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described in Section 3.3.1.3.
3.3.1.1 A double signature zone-signing key rollover
This section shows how to perform a ZSK key using the double zone
data signature scheme.
During the rollover stage the new version of the zone file will need
to propagate to all authoritative servers and the data that existed
in distant caches will need to expire, this will last at least the
maximum Zone TTL .
normal roll after
SOA0 SOA1 SOA2
SIG10(SOA0) SIG10(SOA1) SIG11(SOA2)
SIG11(SOA1)
KEY1 KEY1 KEY1
KEY10 KEY10 KEY11
KEY11
SIG1 (KEY) SIG1 (KEY) SIG1 (KEY)
SIG10(KEY) SIG10(KEY) SIG11(KEY)
SIG11(KEY)
normal: Version 0 of the zone: KEY1 is a key-signing key. Key 10 is
used to sign all the data of the zone, it is the zone-signing key.
roll: At the rollover stage (SOA serial 1) key 11 is introduced into
the keyset and all the data in the zone is signed with KEY 10 and
KEY 11. The rollover period will need to exist until all data
from version 0 of the zone has expired from remote caches. This
will take at least the maximum value of all the TTLs in the
version 0 of the zone.
after: KEY10 is removed from the zone. All the signatures from KEY10
are removed from the zone. The keyset, now only containing KEY11)
is resigned with the KEY1.
At every instance the data from the previous version of the zone can
be verified with the key from the current version. Besides, the data
from the current version can be verified with the data from the
previous version of the zone. The duration of the rollover phase and
the period between rollovers should be at least the "Maximum Zone
TTL".
To be on the safe side one could make sure that the rollover phase
lasts until the signature expiration time of the data in version 0 of
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the zone. But this date could be considerable longer than the TTL,
making the rollover a lengthly procedure.
Note that in this example we assumed that the zone did not get
modified during the rollover. New data can be introduced in the zone
as long as it is signed with both keys.
3.3.1.2 Pre-publish keyset rollover
This section shows how to perform a ZSK key without the need to sign
all the data in ones zone twice. We recommend this method because it
has certain advantages in the case of key compromises. A small
"HOWTO" for this kind of rollover can be found in Appendix B.
normal pre-roll roll after
SOA0 SOA1 SOA2 SOA3
SIG10(SOA0) SIG10(SOA1) SIG11(SOA2) SIG11(SOA3)
KEY1 KEY1 KEY1 KEY1
KEY10 KEY10 KEY10 KEY11
KEY11 KEY11
SIG1 (KEY) SIG1 (KEY) SIG1(KEY) SIG1 (KEY)
SIG10(KEY) SIG10(KEY) SIG11(KEY) SIG11(KEY)
normal: Version 0 of the zone: KEY1 is a key-signing key. Key 10 is
used to sign all the data of the zone, its the zone-signing key.
pre-roll: Key 11 is introduced in the keyset. Note that no
signatures are generated with this key yet, but this will not
prevent brute force attacks on the public key. The minimum
duration of this pre-roll phase is the time it takes for the data
to propagate to the authoritative servers plus TTL value on the
keyset. [FIXME: 3 times the TTL then]
roll:
At the rollover stage (SOA serial 1) KEY 11 is used to sign the
data in the zone (exclusively i.e. all the signatures from KEY10
are removed from the zone.). KEY 10 remains published in the
keyset. This way data that was loaded into caches from version 1
of the zone can still be verified with key sets fetched from
version 2 of the zone.
The minimum time that the keyset that includes KEY 10 is to be
published is the time that it takes for zone data from the
previous version of the zone to expire from old caches i.e. the
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time it takes for this zone to propagate to all authoritative
servers plus the maximum TTL value of any of the data in the
previous version of the zone. [FIXME: 3 times the TTL then?]
after: KEY10 is removed from the zone. The keyset, now only
containing KEY11 is resigned with the KEY1.
The above scheme can be simplified a bit by always publishing the
"future" key immediately after the rollover. The scheme would look
like this (we show 2 rollovers):
normal roll after 2nd roll 2nd after
SOA0 SOA2 SOA3 SOA4 SOA5
SIG10(SOA0) SIG11(SOA2) SIG11(SOA3) SIG12(SOA4) SIG12(SOA5)
KEY1 KEY1 KEY1 KEY1 KEY1
KEY10 KEY10 KEY11 KEY11 KEY12
KEY11 KEY11 KEY12 KEY12 KEY13
SIG1 (KEY) SIG1 (KEY) SIG1(KEY) SIG1(KEY) SIG1(KEY)
SIG10(KEY) SIG11(KEY) SIG11(KEY) SIG12(KEY) SIG12(KEY)
Note that the key introduced after the rollover is not used for
production yet; the private key can thus be stored in a physically
secure space and does not need to be 'fetched' every time a zone
needs to be signed.
This scheme has the benefit that the key that is intended for future
use, can immediately be used during an emergency rollover under the
assumption that it was stored physically secure.
3.3.1.3 Pros and cons of the schemes
A double signature rollover: The drawback of this signing scheme is
that during the rollover the amount of signatures in your zone
doubles, which may be prohibitive if you have very big zones.
Prepublish-keyset rollover. This rollover does not involve signing
the zone data twice, but before the actual rollover the new key is
published in the keyset and thus available for cryptanalysis
attacks.
3.3.2 Key-signing key rollovers
For the rollover of a key-signing key the same considerations as for
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the rollover of a zone-signing key apply. However we can use a
single double signature scheme to guarantee that old data (only the
apex keyset) in caches can be verified with a new keyset and vice
verse.
normal roll after
SOA0 SOA2 SOA3
SIG10(SOA0) SIG11(SOA2) SIG11(SOA3)
KEY1 KEY1 KEY2
KEY2
KEY10 KEY10 KEY11
KEY11 KEY11 KEY12
SIG1 (KEY) SIG1 (KEY) SIG2(KEY)
SIG2 (KEY)
SIG10(KEY) SIG11(KEY) SIG11(KEY)
4. Planning for emergency key rollover.
This section deals with what one has to consider in preparation of a
reaction to a possible key compromise. Our advice is to have a
documented procedure ready for when a key compromise would ever
happen.
[Editors note: We are much in favor of a rollover tactic that keeps
the authentication chain intact as long as possible. This has as a
result that one has to take all the regular rollover properties into
account.]
When the private material of one of your keys is compromised it can
be used by 'blackhats' for as long as a valid authentication chain
exists. A authentication chain remains intact for:
as long as a signature over the compromised key made by another
key in the authentication chain is valid,
as long as a parental DS RR (and signature) points to the
compromised key,
as long as the key is anchored in a resolver and is used as a
starting point for validation. (This is hardest to update.)
While an authentication chain to your compromised key exists your
name-space is vulnerable to abuse by the "black-hat". Zone operators
have to make a trade off if the abuse of the compromised key is worse
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than having data in caches that cannot be validated. If the zone
operator chooses to break the authentication chain to the compromised
key, data in caches signed with this key can not be validated. On
the other hand if the zone administrator chooses to take the path of
a regular roll-over the "black-hat" can spoof data so that it appears
to be valid, note that this kind of attack will usually be localized
in the Internet topology.
4.1 KSK compromise
When the KSK has been compromised the parent must be notified as soon
as possible and in a secure means. The keyset of the zone SHOULD
also be resigned as soon as possible. Care must be taken to not
break the authentication chain. The local zone can only be resigned
with the new KSK when the parent's zone has been updated with the new
KSK. Before this update takes place it would be best to drop the
security status of a zone all together: the parent removes the DS of
the child at the next zone update. After that the child can be made
secure again. An additional danger of a key compromise is that the
compromised key can be used to facilitate a legitemate key/ds and/or
nameserver rollover at the parent. When that happens the domain can
be in dispute. An out of band and secure notify mechanism to contact
a parent is really needed in this case.
4.2 ZSK compromise
Though not as bad as a KSK compromise mainly because there is no
parental interaction required. The zone must still be resigned with
a new ZSK as soon as possible. As this is a local operation and
requires no communication between the parent and child this can be
achieved quickly. One has to take into account though that just as
with a normal rollover immediate disappearance from the old
compromised key may lead to verification problems. The
pre-publication scheme as discussed above minimizes that problem.
4.3 Compromises of keys configured at the resolver level
A key can also be pre-configured in resolvers. If DNSSEC is rolled
out as planned the root key should be pre-configured in every secure
aware resolver on the planet. [Editors Note: add more about
authentication of a newly received resolver key]
If that key is compromised all the resolvers should be notified of
this fact. Zone administrators may consider setting up a mailing
list to communicate the fact that a KSK is about to be rolled over.
This communication will of course need to be secured e.g. by using
digital signatures.
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Key must be removed as soon as possible. Non updated resolver will
have a problem. [Editors Note: this should be extended a bit more]
5. Parental policies.
6. Initial key exchanges and parental policies considerations.
6.1 Storing keys so hashes can be regenerated
6.2 Self signed keys during upload or not?
6.3 Security lameness checks.
6.4 SIG DS validity period.
Since the DS can be replayed as long as it has a valid signature a
short signature validity period over the DS minimizes the time a
child is vulnerable in the case of a compromise of the child's KSK.
A signature validity period that is too short introduces the
possibility that a zone is marked BAD in case of a configuration
error in the signer; there may not be enough time to fix the problems
before signatures expire. Something as mundane as weekends show the
need for a DS signature lifetimes longer than 2 days. We recommend
the minimum for a DS signature validity period to be about 2 days.
The maximum signature lifetime of the DS record depends on how long
child zones are willing to be vulnerable after a key compromise. We
consider a signature validity period of the order of a week a good
compromise between the operational constraints of the parent and
minimizing damage for the child.
7. Resolver key configuration.
Zone keys may be hard configured in resolver configurations. In case
of a compromise of a SEP key these "distant" resolvers will need to
be informed of a compromise and will need to take appropriate action.
A special purpose maillist on which such a compromise can be
announced (securely) and a set of procedures for securely publishing
the new SEP key should be considered.
8. Security considerations
DNSSEC adds data integrity to the DNS. This document tries to assess
considerations to operate a stable and secure DNSSEC service.
9. Acknowledgments
We, the folk mentioned as authors, only acted as editors. Most of
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the ideas in this draft where the result of collective efforts during
workshops and discussions and try outs.
At the risk of forgetting individuals who where the original
contributors of the ideas we like to acknowledge people who where
actively involved in the compilation of this document. In
alphabetical order: Olafur Gudmundsson, Wesley Griffin.
Kolkman and Gieben take the blame for all mistakes.
Normative References
[1] Eastlake, D., "Domain Name System Security Extensions", RFC
2535, March 1999.
[2] Eastlake, D., "DNS Security Operational Considerations", RFC
2541, March 1999.
[3] Lewis, E., "DNS Security Extension Clarification on Zone
Status", RFC 3090, March 2001.
[4] Lewis, E., Kolkman, O. and J. Schlyter, "KEY RR Key-Signing Key
(KSK) Flag", draft-ietf-dnsext-keyrr-key-signing-flag-06 (work
in progress), February 2003.
Informative References
[5] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[6] Andrews, M., "Negative Caching of DNS Queries (DNS NCACHE)", RFC
2308, March 1998.
[7] Gudmundsson, O., "Delegation Signer Resource Record",
draft-ietf-dnsext-delegation-signer-13 (work in progress), March
2003.
[8] Arends, R., "Protocol Modifications for the DNS Security
Extensions", draft-ietf-dnsext-dnssec-protocol-01 (work in
progress), March 2003.
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Authors' Addresses
Olaf M. Kolkman
RIPE NCC
Singel 256
Amsterdam 1016 AB
NL
Phone: +31 20 535 4444
EMail: olaf@ripe.net
URI: http://www.ripe.net/
Miek Gieben
NLnet Labs
Kruislaan 419
Amsterdam 1098 VA
NL
EMail: miek@nlnetlabs.nl
URI: http://www.nlnetlabs.nl
Appendix A. Terminology
In this document there is some jargon used that is defined in other
documents. In most cases we have not copied the text from the
documents defining the terms but give a more elaborate explanation of
the meaning. Note that these explanations should not be seen as
authoritative.
Private and Public Keys: DNSSEC secures the DNS through the use of
public key cryptography. Public key cryptography is based on the
existence of 2 keys, a public key and a private key. The public
keys are published in the DNS by use of the KEY Resource Record
(KEY RR). Private keys are supposed to remain private i.e.
should not be exposed to parties not-authorized to do the actual
signing.
Signer: The system that has access to the private key material and
signs the Resource Record sets in a zone. A signer may be
configured to sign only parts of the zone e.g. only those RRsets
for which existing signatures are about to expire.
KSK: A Key-Signing key (KSK) is a key that is used for exclusively
signing the apex keyset. The fact that a key is a KSK is only
relevant to the signing tool.
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ZSK: A Zone signing key (ZSK) is a key that is used for signing all
data in a zone. The fact that a key is a ZSK is only relevant to
the signing tool.
Singing Zone Rollover: The term used for the event where an
administrator joyfully rolls over the keys while producing melodic
sound patterns.
Appendix B. Zone-signing key rollover howto
Using the pre-published signature scheme and the most conservative
method to assure oneself that data does not live in distant caches
here follows the "HOWTO". [WES: has some comments about this]
STEP 0, the preparation: Create two keys and publish them both in
your keyset. Mark one of the keys as "active" and the other as
"published". Use the "active" key for signing your zone data.
Store the private part of the "published" key, preferably
off-line.
STEP 1, determine expiration: At the beginning of the rollover:
make a note of the highest expiration time of signatures in your
zonefile created with the current key currently marked as
"active".
Wait until the expiration time marked in STEP 1
STEP 2 Then start using the key that was marked as "published" to
sign your data i.e. mark it as "active". Stop using the key that
was marked as "active", mark it as "rolled".
STEP 3: It is safe to engage in a new rollover (STEP 1) after at
least "signature validity period".
Appendix C. Typographic conventions
The following typographic conventions are used in this document:
Key notation: A key is denoted by KEYx, where x is a number, x could
be thought of as the key id.
Signature notation: Signatures are denoted as SIGx(RRset), which
means that RRset is signed with KEYx.
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Optionally the RRset can be written in full: SIG1(KEY1, KEY2).
Which is the signature made with KEY1 over the keyset containing
KEY1 and KEY2.
Zone representation: Using the above notation we have simplify the
representation of a signed ZONE by leaving out all unneeded
details such as the names and by just representing all non zone
apex data by "ZD" (Zone Data).
SOA representation: Soa's are represented as SOA x, where x is the
serial number.
Using this notation the following zone :
example.net. 600 IN SOA ns.example.net. ernie.example.net. (
10 ; serial
450 ; refresh (7 minutes 30 seconds)
600 ; retry (10 minutes)
345600 ; expire (4 days)
300 ; minimum (5 minutes)
)
600 SIG SOA 5 2 600 20130522213204 (
20130422213204 14 example.net.
cmL62SI6iAX46xGNQAdQ... )
600 NS a.iana-servers.net.
600 NS b.iana-servers.net.
600 SIG NS 5 2 600 20130507213204 (
20130407213204 14 example.net.
SO5epiJei19AjXoUpFnQ ... )
3600 KEY 256 3 5 (
EtRB9MP5/AvOuVO0I8XDxy0...
) ; key id = 14
3600 KEY 256 3 5 (
gsPW/Yy19GzYIY+Gnr8HABU...
) ; key id = 15
3600 SIG KEY 5 2 3600 20130522213204 (
20130422213204 14 example.net.
J4zCe8QX4tXVGjV4e1r9... )
3600 SIG KEY 5 2 3600 20130522213204 (
20130422213204 15 example.net.
keVDCOpsSeDReyV6O... )
600 NXT a.example.net. NS SOA TXT SIG KEY NXT
600 SIG NXT 5 2 600 20130507213204 (
20130407213204 14 example.net.
obj3HEp1GjnmhRjX... )
a.example.net. 600 IN TXT "A label"
600 SIG TXT 5 3 600 20130507213204 (
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20130407213204 14 example.net.
IkDMlRdYLmXH7QJnuF3v... )
600 NXT b.example.com. TXT SIG NXT
600 SIG NXT 5 3 600 20130507213204 (
20130407213204 14 example.net.
bZMjoZ3bHjnEz0nIsPMM... )
...
is reduced to the following represenation:
SOA10
SIG14(SOA10)
KEY14
KEY15
SIG14(KEY)
SIG15(KEY)
The rest of the zone data has the same signature as the SOA record.
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