draft-ietf-dnsop-dnssec-key-timing-04.txt   draft-ietf-dnsop-dnssec-key-timing-05.txt 
Internet Engineering Task Force S. Morris Internet Engineering Task Force S. Morris
Internet-Draft ISC Internet-Draft ISC
Intended status: Informational J. Ihren Intended status: Informational J. Ihren
Expires: January 5, 2015 Netnod Expires: March 21, 2015 Netnod
J. Dickinson J. Dickinson
Sinodun Sinodun
W. Mekking W. Mekking
NLnet Labs NLnet Labs
July 4, 2014 September 17, 2014
DNSSEC Key Rollover Timing Considerations DNSSEC Key Rollover Timing Considerations
draft-ietf-dnsop-dnssec-key-timing-04.txt draft-ietf-dnsop-dnssec-key-timing-05.txt
Abstract Abstract
This document describes the issues surrounding the timing of events This document describes the issues surrounding the timing of events
in the rolling of a key in a DNSSEC-secured zone. It presents in the rolling of a key in a DNSSEC-secured zone. It presents
timelines for the key rollover and explicitly identifies the timelines for the key rollover and explicitly identifies the
relationships between the various parameters affecting the process. relationships between the various parameters affecting the process.
Status of This Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 5, 2015. This Internet-Draft will expire on March 21, 2015.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Key Rolling Considerations . . . . . . . . . . . . . . . 2 1.1. Key Rolling Considerations . . . . . . . . . . . . . . . . 3
1.2. Types of Keys . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Types of Keys . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Rollover Methods . . . . . . . . . . . . . . . . . . . . . . 4 2. Rollover Methods . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. ZSK Rollovers . . . . . . . . . . . . . . . . . . . . . . 4 2.1. ZSK Rollovers . . . . . . . . . . . . . . . . . . . . . . 4
2.2. KSK Rollovers . . . . . . . . . . . . . . . . . . . . . . 6 2.2. KSK Rollovers . . . . . . . . . . . . . . . . . . . . . . 6
3. Key Rollover Timelines . . . . . . . . . . . . . . . . . . . 7 3. Key Rollover Timelines . . . . . . . . . . . . . . . . . . . . 7
3.1. Key States . . . . . . . . . . . . . . . . . . . . . . . 7 3.1. Key States . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Zone-Signing Key Timelines . . . . . . . . . . . . . . . 8 3.2. Zone-Signing Key Timelines . . . . . . . . . . . . . . . . 9
3.2.1. Pre-Publication Method . . . . . . . . . . . . . . . 8 3.2.1. Pre-Publication Method . . . . . . . . . . . . . . . . 9
3.2.2. Double-Signature Method . . . . . . . . . . . . . . . 11 3.2.2. Double-Signature Method . . . . . . . . . . . . . . . 12
3.3. Key-Signing Key Rollover Timelines . . . . . . . . . . . 13 3.3. Key-Signing Key Rollover Timelines . . . . . . . . . . . . 13
3.3.1. Double-KSK Method . . . . . . . . . . . . . . . . . . 13 3.3.1. Double-KSK Method . . . . . . . . . . . . . . . . . . 14
3.3.2. Double-DS Method . . . . . . . . . . . . . . . . . . 16 3.3.2. Double-DS Method . . . . . . . . . . . . . . . . . . . 16
3.3.3. Double-RRset Method . . . . . . . . . . . . . . . . . 19 3.3.3. Double-RRset Method . . . . . . . . . . . . . . . . . 19
3.3.4. Interaction with Configured Trust Anchors . . . . . . 21 3.3.4. Interaction with Configured Trust Anchors . . . . . . 21
3.3.5. Introduction of First Keys . . . . . . . . . . . . . 23 3.3.5. Introduction of First Keys . . . . . . . . . . . . . . 22
4. Standby Keys . . . . . . . . . . . . . . . . . . . . . . . . 23 4. Standby Keys . . . . . . . . . . . . . . . . . . . . . . . . . 22
5. Algorithm Considerations . . . . . . . . . . . . . . . . . . 24 5. Algorithm Considerations . . . . . . . . . . . . . . . . . . . 23
6. Limitation of Scope . . . . . . . . . . . . . . . . . . . . . 24 6. Limitation of Scope . . . . . . . . . . . . . . . . . . . . . 24
7. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 7. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
9. Security Considerations . . . . . . . . . . . . . . . . . . . 25 9. Security Considerations . . . . . . . . . . . . . . . . . . . 25
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
11. Normative References . . . . . . . . . . . . . . . . . . . . 26 11. Normative References . . . . . . . . . . . . . . . . . . . . . 25
Appendix A. List of Symbols . . . . . . . . . . . . . . . . . . 26 Appendix A. List of Symbols . . . . . . . . . . . . . . . . . . . 26
Appendix B. Change History (To be removed on publication) . . . 29 Appendix B. Change History (To be removed on publication) . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31
1. Introduction 1. Introduction
1.1. Key Rolling Considerations 1.1. Key Rolling Considerations
When a zone is secured with DNSSEC, the zone manager must be prepared When a zone is secured with DNSSEC, the zone manager must be prepared
to replace ("roll") the keys used in the signing process. The to replace ("roll") the keys used in the signing process. The
rolling of keys may be caused by compromise of one or more of the rolling of keys may be caused by compromise of one or more of the
existing keys, or it may be due to a management policy that demands existing keys, or it may be due to a management policy that demands
periodic key replacement for security or operational reasons. In periodic key replacement for security or operational reasons. In
order to implement a key rollover, the keys need to be introduced order to implement a key rollover, the keys need to be introduced
into and removed from the zone at the appropriate times. into and removed from the zone at the appropriate times.
Considerations that must be taken into account are: Considerations that must be taken into account are:
o DNSKEY records and associated information (such as the associated o DNSKEY records and associated information (such as the DS records
DS records or RRSIG records created with the key) are not only or RRSIG records created with the key) are not only held at the
held at the authoritative nameserver, they are also cached by authoritative nameserver, they are also cached by resolvers. The
resolvers. The data on these systems can be interlinked, e.g., a data on these systems can be interlinked, e.g., a validating
validating resolver may try to validate a signature retrieved from resolver may try to validate a signature retrieved from a cache
a cache with a key obtained separately. with a key obtained separately.
o Zone "boot-strapping" events, where a zone is signed for the first o Zone "boot-strapping" events, where a zone is signed for the first
time, can be common in configurations where a large number of time, can be common in configurations where a large number of
zones are being served. Procedures should be able to cope with zones are being served. Procedures should be able to cope with
the introduction of keys into the zone for the first time as well the introduction of keys into the zone for the first time as well
as "steady-state", where the records are being replaced as part of as "steady-state", where the records are being replaced as part of
normal zone maintenance. normal zone maintenance.
o To allow for an emergency re-signing of the zone as soon as o To allow for an emergency re-signing of the zone as soon as
possible after a key compromise has been detected, standby keys possible after a key compromise has been detected, standby keys
skipping to change at page 3, line 40 skipping to change at page 3, line 51
zone should be restricted to the minimum required to support the zone should be restricted to the minimum required to support the
key management policy.) key management policy.)
Management policy, e.g., how long a key is used for, also needs to be Management policy, e.g., how long a key is used for, also needs to be
considered. However, the point of key management logic is not to considered. However, the point of key management logic is not to
ensure that a rollover is completed at a certain time but rather to ensure that a rollover is completed at a certain time but rather to
ensure that no changes are made to the state of keys published in the ensure that no changes are made to the state of keys published in the
zone until it is "safe" to do so ("safe" in this context meaning that zone until it is "safe" to do so ("safe" in this context meaning that
at no time during the rollover process does any part of the zone ever at no time during the rollover process does any part of the zone ever
go bogus). In other words, although key management logic enforces go bogus). In other words, although key management logic enforces
policy, it may not enforce it strictly. In Section 3, the lifetime policy, it may not enforce it strictly.
of a key reflects the actual lifetime of a key, which may be longer
or shorter than the intended amount of time.
A high-level overview of key rollover can be found in [RFC6781]. In A high-level overview of key rollover can be found in [RFC6781]. In
contrast, this document focuses on the low-level timing detail of two contrast, this document focuses on the low-level timing detail of two
classes of operations described there, the rollover of zone-signing classes of operations described there, the rollover of zone-signing
keys (ZSKs), and the rollover of key-signing keys (KSKs). keys (ZSKs), and the rollover of key-signing keys (KSKs).
1.2. Types of Keys 1.2. Types of Keys
Although DNSSEC validation treats all keys equally, [RFC4033] Although DNSSEC validation treats all keys equally, [RFC4033]
recognises the broad classification of ZSKs and KSKs. A ZSK is used recognises the broad classification of ZSKs and KSKs. A ZSK is used
skipping to change at page 5, line 28 skipping to change at page 5, line 35
introducing the new key into the zone and using it to create introducing the new key into the zone and using it to create
additional RRSIG records; the old key and existing RRSIG records additional RRSIG records; the old key and existing RRSIG records
are retained. During the period in which the zone is being signed are retained. During the period in which the zone is being signed
(again, the signing process may not be atomic), validating (again, the signing process may not be atomic), validating
resolvers are always able to validate RRSIGs: any combination of resolvers are always able to validate RRSIGs: any combination of
old and new DNSKEY RRset and RRSIGs allows at least one signature old and new DNSKEY RRset and RRSIGs allows at least one signature
to be validated. to be validated.
Once the signing process is complete and enough time has elapsed Once the signing process is complete and enough time has elapsed
to make sure that all validators that have the DNSKEY and to make sure that all validators that have the DNSKEY and
signatures in cache, have both the old and new information, the signatures in cache have both the old and new information, the old
old key and signatures can be removed from the zone. As before, key and signatures can be removed from the zone. As before,
during this period any combination of DNSKEY RRset and RRSIGs will during this period any combination of DNSKEY RRset and RRSIGs will
allow validation of at least one signature. allow validation of at least one signature.
o Double-RRSIG: strictly speaking, the use of the term "Double- o Double-RRSIG: strictly speaking, the use of the term "Double-
Signature" above is a misnomer as the method is not only double Signature" above is a misnomer as the method is not only double
signature, it is also double key as well. A true Double-Signature signature, it is also double key as well. A true Double-Signature
method (here called the Double-RRSIG method) involves introducing method (here called the Double-RRSIG method) involves introducing
new signatures in the zone (while still retaining the old ones) new signatures in the zone (while still retaining the old ones)
but not introducing the new key. but not introducing the new key.
skipping to change at page 7, line 22 skipping to change at page 7, line 27
change to propagate into caches, the KSK is changed. After a change to propagate into caches, the KSK is changed. After a
further interval during which the old DNSKEY RRset expires from further interval during which the old DNSKEY RRset expires from
caches, the old DS record is removed. caches, the old DS record is removed.
o Double-RRset: the new KSK is added to the DNSKEY RRset which is o Double-RRset: the new KSK is added to the DNSKEY RRset which is
then signed with both the old and new key, and the new DS record then signed with both the old and new key, and the new DS record
added to the parent zone. After waiting a suitable interval for added to the parent zone. After waiting a suitable interval for
the old DS and DNSKEY RRsets to expire from caches, the old DNSKEY the old DS and DNSKEY RRsets to expire from caches, the old DNSKEY
and DS record are removed. and DS record are removed.
In essence, "Double-KSK" means that the new KSK is introduced first In essence, Double-KSK means that the new KSK is introduced first and
and used to sign the DNSKEY RRset. The DS record is changed, and used to sign the DNSKEY RRset. The DS record is changed, and finally
finally the old KSK removed. With "Double-DS" it is the other way the old KSK removed. It limits interactions with the parent to a
around. Finally, Double-RRset does both updates more or less in minimum but, for the duration of the rollover, the size of the DNSKEY
parallel. RRset is increased.
Of the three methods, the major disadvantages are the number of times With Double-DS, the order of operations is the other way round:
you have to contact the parent and the size of the DNSKEY RRset. In introduce the new DS, change the DNSKEY, then remove the old DS. The
Double-Signature there is just one parent interaction but there is a size of the DNSKEY RRset is kept to a minimum, but two interactions
larger DNSKEY RRset. In the case of Double-DS there are two are required with the parent.
interactions with the parent (although the second one does not slow
down your rollover). The Double-RRset is the fastest, but has both Finally, Double-RRset is the fastest way to roll the KSK, but has the
the disadvantages of the other two methods. drawbacks of both of the other methods: a larger DNSKEY RRset and two
interactions with the parent.
3. Key Rollover Timelines 3. Key Rollover Timelines
3.1. Key States 3.1. Key States
A DNSSEC key contributes two pieces of information to the validation
process: the DNSKEY itself and the data created from it. In the case
of the validation of an RR, the data created from the DNSKEY is the
RRSIG. Where there is a need to validate a chain or trust, the data
created from the DNSKEY is the DS. In this section, the term
"associated data" refers to the RRSIGs created from a DNSKEY when
discussing a ZSK, or to the DNSKEY's corresponding DS record when
referring to a KSK.
During the rolling process, keys move through different states. The During the rolling process, keys move through different states. The
defined states are: defined states are:
Generated The key has been created, but has not yet been used for Generated Although keys may be created immediately prior to first
anything. use, some implementations may find it convenient to
create a pool of keys in one operation and draw from it
as required. (Note: such a pre-generated pool must be
secured against surreptitious use.) Keys that have been
created but not yet used are said to be in the
"Generated" state.
Published The DNSKEY and/or DS record is published in the zone. Published A key enters the published state when either it or its
associated data first appears in the appropriate zone.
Ready The DNSKEY and/or DS record have been published for long Ready The DNSKEY or its associated data have been published for
enough to guarantee that any previous versions of the long enough to guarantee that any previous versions of
DNSKEY RRset have expired from caches. the DNSKEY and/or associated data have expired from
caches.
Active The data is starting to be used for validation. In the Active The data is starting to be used for validation. In the
case of a ZSK, it means that the key has been started to case of a ZSK, it means that the key is now being be used
be used to sign RRsets. In the case of a KSK, it means to sign RRsets and that both it and the created RRSIGs
that it is possible to use it to validate a DNSKEY RRset appear in the zone. In the case of a KSK, it means that
as the DNSKEY and DS records are present in the relevant it is possible to use it to validate a DNSKEY RRset as
zones. Note that when this state is entered, it may not both the DNSKEY and DS records are present in their
be possible for validating resolvers to use the data for relevant zones. Note that when this state is entered, it
validation in all cases: the zone signing may not have may not be possible for validating resolvers to use the
finished, or the data might not have reached the resolver data for validation in all cases: the zone signing may
because of propagation delays and/or caching issues. If not have finished, or the data might not have reached the
this is the case, the resolver will have to rely on the resolver because of propagation delays and/or caching
predecessor data instead. issues. If this is the case, the resolver will have to
rely on the predecessor data instead.
Retired The data has ceased to be used for validation. In the Retired The data has ceased to be used for validation. In the
case of a ZSK, it means that the key is no longer used to case of a ZSK, it means that the key is no longer used to
sign RRsets. In the case of a KSK, it means that the sign RRsets. In the case of a KSK, it means that the
successor DNSKEY and DS records are in place: this key successor DNSKEY and DS records are in place. In both
and its DS record can be removed as soon as it is safe to cases, the key (and its associated data) can be removed
do so. However, until this happens, the resource records as soon as it is safe to do so, i.e. when all validating
may still available for use in validation. resolvers are able to use the new key and associated data
to validate the zone. However, until this happens, the
current key and associated data must remain in their
respective zones.
Dead The DNSKEY and/or DS record are present in the zone but Dead The key and is associated data are present in their
there is no longer information anywhere that requires its respective zones, but there is no longer information
presence for use in validation. Hence it can be removed anywhere that require their presence for use in
from the zone at any time. validation. Hence they can be removed at any time.
Removed The DNSKEY and/or DS record have been removed from the Removed Both the DNSKEY and its associated data have been removed
zone. from their respective zones.
There is one additional state, used where [RFC5011] considerations There is one additional state, used where [RFC5011] considerations
are in effect (see Section 3.3.4): are in effect (see Section 3.3.4):
Revoked The DNSKEY is published for a period with the "revoke" Revoked The DNSKEY is published for a period with the "revoke"
bit set as a way of notifying validating resolvers that bit set as a way of notifying validating resolvers that
have configured it as an [RFC5011] trust anchor that it have configured it as an [RFC5011] trust anchor that it
is about to be removed from the zone. is about to be removed from the zone.
3.2. Zone-Signing Key Timelines 3.2. Zone-Signing Key Timelines
The following sections describe the rolling of a ZSK. They show the The following sections describe the rolling of a ZSK. They show the
events in the lifetime of a key (referred to as "key N") and cover events in the lifetime of a key (referred to as "key N") and cover
its replacement by its successor (key N+1). its replacement by its successor (key N+1).
3.2.1. Pre-Publication Method 3.2.1. Pre-Publication Method
In this method, the new key is introduced into the DNSKEY RRset. In this method, the new key is introduced into the DNSKEY RRset.
After enough time to ensure that any cached DNSKEY RRsets contain After enough time to ensure that any cached DNSKEY RRsets contain
both keys, the the zone is signed using the new key and the old both keys, the zone is signed using the new key and the old
signatures are removed. Finally, when all signatures created with signatures are removed. Finally, when all signatures created with
the old key have expired from caches, the old key is removed. the old key have expired from caches, the old key is removed.
The following diagram shows the timeline of a Pre-Publication The following diagram shows the timeline of a Pre-Publication
rollover. Time increases along the horizontal scale from left to rollover. Time increases along the horizontal scale from left to
right and the vertical lines indicate events in the process. right and the vertical lines indicate events in the process.
Significant times and time intervals are marked. Significant times and time intervals are marked.
|0| |1| |2| |3| |4| |5| |6| |7| |8| |1| |2| |3| |4| |5| |6| |7| |8|
| | | | | | | | | | | | | | | | |
Key N | |<-Ipub->|<--->|<-------Lzsk------>|<-Iret->|<--->| Key N |<-Ipub->|<--->|<-------Lzsk------>|<-Iret->|<--->|
| | | | | | | | | | | | | | | | |
Key N+1 | | | | |<-Ipub->|<-->|<---Lzsk---- - - Key N+1 | | | |<-Ipub->|<-->|<---Lzsk---- - -
| | | | | | | | | | | | | | | | |
Key N Tgen Tpub Trdy Tact Tret Tdea Trem Key N Tpub Trdy Tact Tret Tdea Trem
Key N+1 Tgen Tpub Trdy Tact Key N+1 Tpub Trdy Tact
---- Time ----> ---- Time ---->
Figure 1: Timeline for a Pre-Publication ZSK rollover. Figure 1: Timeline for a Pre-Publication ZSK rollover.
Event 0: Key N and N+1 are generated at the generate time (Tgen). Event 1: Key N's DNSKEY record is put into the zone, i.e. it is added
Although there is no reason why the key cannot be generated to the DNSKEY RRset which is then re-signed with the currently active
immediately prior to its publication in the zone (Event 1), some key-signing keys. The time at which this occurs is the publication
implementations may find it convenient to create a pool of keys in time (Tpub), and the key is now said to be published. Note that the
one operation and draw from that pool as required. For this reason, key is not yet used to sign records.
it is shown as a separate event. Keys that are available for use but
not published are said to be generated.
Event 1: Key N's DNSKEY record is put into the zone, i.e., it is
added to the DNSKEY RRset which is then re-signed with the current
active key-signing keys. The time at which this occurs is the key's
publication time (Tpub), and the key is now said to be published.
Note that the key is not yet used to sign records.
Event 2: Before it can be used, the key must be published for long Event 2: Before it can be used, the key must be published for long
enough to guarantee that any cached version of the zone's DNSKEY enough to guarantee that any cached version of the zone's DNSKEY
RRset includes this key. RRset includes this key.
This interval is the publication interval (Ipub) and, for the second This interval is the publication interval (Ipub) and, for the second
or subsequent keys in the zone, is given by: or subsequent keys in the zone, is given by:
Ipub = Dprp + TTLkey Ipub = Dprp + TTLkey
Here, Dprp is the propagation delay - the time taken for a change Here, Dprp is the propagation delay - the time taken for a change
introduced at the master to replicate to all name servers. TTLkey is introduced at the master to replicate to all name servers. TTLkey is
the time-to-live (TTL) for the DNSKEY records in the zone. The sum the time-to-live (TTL) for the DNSKEY records in the zone. The sum
is therefore the maximum time taken for existing DNSKEY records to is therefore the maximum time taken for existing DNSKEY records to
expire from caches, regardless of the nameserver from which they were expire from caches, regardless of the nameserver from which they were
retrieved. retrieved.
(The case of introducing the first ZSK into the zone is discussed in (The case of introducing the first ZSK into the zone is discussed in
Section 3.3.5.) Section 3.3.5.)
After a delay of Ipub, the key is said to be ready and could be used After a delay of Ipub, the key is said to be ready and could be used
to sign records. The time at which this event occurs is key N's to sign records. The time at which this event occurs is key N's
ready time (Trdy), which is given by: ready time (Trdy), which is given by:
Trdy(N) = Tpub(N) + Ipub Trdy(N) = Tpub(N) + Ipub
Event 3: At some later time, the key starts being used to sign Event 3: At some later time, the key starts being used to sign
RRsets. This point is the activation time (Tact) and after this, key RRsets. This point is the activation time (Tact) and after this, key
N is said to be active. N is said to be active.
Tact(N) >= Trdy(N) Tact(N) >= Trdy(N)
Event 4: At some point thought must be given to its successor (key Event 4: At some point thought must be given to its successor (key
N+1). As with the introduction of the currently active key into the N+1). As with the introduction of the currently active key into the
zone, the successor key will need to be published at least Ipub zone, the successor key will need to be published at least Ipub
before it is activated. The publication time of key N+1 depends on before it is activated. The publication time of key N+1 depends on
the activation time of key N: the activation time of key N:
Tpub(N+1) <= Tact(N) + Lzsk - Ipub Tpub(N+1) <= Tact(N) + Lzsk - Ipub
Here, Lzsk is the length of time for which a ZSK will be used (the Here, Lzsk is the length of time for which a ZSK will be used (the
ZSK lifetime). It should be noted that in the diagrams the actual ZSK lifetime). It should be noted that in the diagrams the actual
key lifetime is represented; this may differ slightly from the key lifetime is represented; this may differ slightly from the
intended lifetime set by key management policy. intended lifetime set by key management policy.
Event 5: While key N is still active, its successor becomes ready. Event 5: While key N is still active, its successor becomes ready.
From this time onwards, key N+1 could be used to sign the zone. From this time onwards, key N+1 could be used to sign the zone.
Event 6: When key N has been in use for an interval equal to the ZSK Event 6: When key N has been in use for an interval equal to the ZSK
lifetime, it is retired (i.e., it will never again be used to lifetime, it is retired (i.e. it will never again be used to generate
generate new signatures) and key N+1 activated and used to sign the new signatures) and key N+1 activated and used to sign the zone.
zone. This is the retire time of key N (Tret), and is given by: This is the retire time of key N (Tret), and is given by:
Tret(N) = Tact(N) + Lzsk Tret(N) = Tact(N) + Lzsk
It is also the activation time of the successor key N+1. Note that It is also the activation time of the successor key N+1. Note that
operational considerations may cause key N to remain in use for operational considerations may cause key N to remain in use for a
longer than the lifetime set by the key management policy. longer (or shorter) time than the lifetime set by the key management
policy.
Event 7: The retired key needs to be retained in the zone whilst any Event 7: The retired key needs to be retained in the zone whilst any
RRSIG records created using this key are still published in the zone RRSIG records created using this key are still published in the zone
or held in caches. (It is possible that a validating resolver could or held in caches. (It is possible that a validating resolver could
have an old RRSIG record in the cache, but the old DNSKEY RRset has have an old RRSIG record in the cache, but the old DNSKEY RRset has
expired when it is asked to provide both to a client. In this case expired when it is asked to provide both to a client. In this case
the DNSKEY RRset would need to be looked up again.) This means that the DNSKEY RRset would need to be looked up again.) This means that
once the key is no longer used to sign records, it should be retained once the key is no longer used to sign records, it should be retained
in the zone for at least the retire interval (Iret) given by: in the zone for at least the retire interval (Iret) given by:
Iret = Dsgn + Dprp + TTLsig Iret = Dsgn + Dprp + TTLsig
Dsgn is the delay needed to ensure that all existing RRsets have been Dsgn is the delay needed to ensure that all existing RRsets have been
re-signed with the new key. Dprp is the propagation delay, required re-signed with the new key. Dprp is the propagation delay, required
to guarantee that the updated zone information has reached all slave to guarantee that the updated zone information has reached all slave
servers, and TTLsig is the maximum TTL of all the RRSIG records in servers, and TTLsig is the maximum TTL of all the RRSIG records in
the zone created with the retiring key. the zone created with the retiring key.
The time at which all RRSIG records created with this key have The time at which all RRSIG records created with this key have
expired from resolver caches is the dead time (Tdea), given by: expired from resolver caches is the dead time (Tdea), given by:
Tdea(N) = Tret(N) + Iret Tdea(N) = Tret(N) + Iret
... at which point the key is said to be dead. ... at which point the key is said to be dead.
Event 8: At any time after the key becomes dead, it can be removed Event 8: At any time after the key becomes dead, it can be removed
from the zone's DNSKEY RRset, which must then be re-signed with the from the zone's DNSKEY RRset, which must then be re-signed with the
current key-signing key. This time is the removal time (Trem), given current key-signing key. This time is the removal time (Trem), given
by: by:
Trem(N) >= Tdea(N) Trem(N) >= Tdea(N)
... at which time the key is said to be removed. ... at which time the key is said to be removed.
3.2.2. Double-Signature Method 3.2.2. Double-Signature Method
In this rollover, a new key is introduced and used to sign the zone; In this rollover, a new key is introduced and used to sign the zone;
the old key and signatures are retained. Once all cached DNSKEY and/ the old key and signatures are retained. Once all cached DNSKEY
or RRSIG information contains copies of the new DNSKEY and RRSIGs and/or RRSIG information contains copies of the new DNSKEY and RRSIGs
created with it, the old DNSKEY and RRSIGs can be removed from the created with it, the old DNSKEY and RRSIGs can be removed from the
zone. zone.
The timeline for a double-signature rollover is shown below. The The timeline for a double-signature rollover is shown below. The
diagram follows the convention described in Section 3.2.1 diagram follows the convention described in Section 3.2.1
|0| |1| |2| |3| |4|
| | | | | |1| |2| |3| |4|
Key N | |<-------Lzsk----------->|<--->| | | | |
| | | | | Key N |<-------Lzsk----------->|<--->|
| | |<--Iret-->| | | | | |
| | | | | | |<--Iret-->| |
Key N+1 | | |<----Lzsk------- - - | | | |
| | | | | Key N+1 | |<----Lzsk------- - -
Key N Tgen Tact Tdea Trem | | | |
Key N+1 Tgen Tact Key N Tact Tdea Trem
Key N+1 Tact
---- Time ----> ---- Time ---->
Figure 2: Timeline for a Double-Signature ZSK rollover. Figure 2: Timeline for a Double-Signature ZSK rollover.
Event 0: Key N and N+1 are generated at the generate time (Tgen).
Although there is no reason why the key cannot be generated
immediately prior to its publication in the zone (Event 1), some
implementations may find it convenient to create a pool of keys in
one operation and draw from that pool as required. For this reason,
it is shown as a separate event. Keys that are available for use but
not published are said to be generated.
Event 1: Key N is added to the DNSKEY RRset and is then used to sign Event 1: Key N is added to the DNSKEY RRset and is then used to sign
the zone; existing signatures in the zone are not removed. The key the zone; existing signatures in the zone are not removed. The key
is published and active: this is key N's activation time (Tact), is published and active: this is key N's activation time (Tact),
after which the key is said to be active. after which the key is said to be active.
Event 2: As the current key (key N) approaches the end of its actual Event 2: As the current key (key N) approaches the end of its actual
lifetime (Lzsk), the successor key (key N+1) is introduced into the lifetime (Lzsk), the successor key (key N+1) is introduced into the
zone and starts being used to sign RRsets: neither the current key zone and starts being used to sign RRsets: neither the current key
nor the signatures created with it are removed. The successor key is nor the signatures created with it are removed. The successor key is
now also active. now also active.
Tact(N+1) = Tact(N) + Lzsk - Iret Tact(N+1) = Tact(N) + Lzsk - Iret
Event 3: Before key N can be withdrawn from the zone, all RRsets that Event 3: Before key N can be withdrawn from the zone, all RRsets that
need to be signed must have been signed by the successor key (key need to be signed must have been signed by the successor key (key
N+1) and any old RRsets that do not include the new key or new RRSIGs N+1) and any old RRsets that do not include the new key or new RRSIGs
must have expired from caches. Note that the signatures are not must have expired from caches. Note that the signatures are not
replaced - each RRset is signed by both the old and new key. replaced - each RRset is signed by both the old and new key.
This takes Iret, the retire interval, given by the expression: This takes Iret, the retire interval, given by the expression:
Iret = Dsgn + Dprp + max(TTLkey, TTLsig) Iret = Dsgn + Dprp + max(TTLkey, TTLsig)
As before, Dsgn is the delay needed to ensure that all existing As before, Dsgn is the delay needed to ensure that all existing
RRsets have been signed with the new key and Dprp is the propagation RRsets have been signed with the new key and Dprp is the propagation
delay, required to guarantee that the updated zone information has delay, required to guarantee that the updated zone information has
reached all slave servers. The final term (the maximum of TTLkey and reached all slave servers. The final term (the maximum of TTLkey and
TTLsig) is the period to wait for key and signature data associated TTLsig) is the period to wait for key and signature data associated
with key N to expire from caches. (TTLkey is the TTL of the DNSKEY with key N to expire from caches. (TTLkey is the TTL of the DNSKEY
RRset and TTLsig is the maximum TTL of all the RRSIG records in the RRset and TTLsig is the maximum TTL of all the RRSIG records in the
zone created with the ZSK. The two may be different: although the zone created with the ZSK. The two may be different: although the
TTL of an RRSIG is equal to the TTL of the RRs in the associated TTL of an RRSIG is equal to the TTL of the RRs in the associated
RRset [RFC4034], the DNSKEY RRset only needs to be signed with the RRset [RFC4034], the DNSKEY RRset only needs to be signed with the
KSK.) KSK.)
At the end of this interval, key N is said to be dead. This occurs At the end of this interval, key N is said to be dead. This occurs
at the dead time (Tdea) so: at the dead time (Tdea) so:
Tdea(N) = Tact(N+1) + Iret Tdea(N) = Tact(N+1) + Iret
Event 4: At some later time key N and the signatures generated with Event 4: At some later time key N and the signatures generated with
it can be removed from the zone. This is the removal time (Trem), it can be removed from the zone. This is the removal time (Trem),
given by: given by:
Trem(N) >= Tdea(N) Trem(N) >= Tdea(N)
3.3. Key-Signing Key Rollover Timelines 3.3. Key-Signing Key Rollover Timelines
The following sections describe the rolling of a KSK. They show the The following sections describe the rolling of a KSK. They show the
events in the lifetime of a key (referred to as "key N") and cover it events in the lifetime of a key (referred to as "key N") and cover it
replacement by its successor (key N+1). replacement by its successor (key N+1). (The case of introducing the
first KSK into the zone is discussed in Section 3.3.5.)
3.3.1. Double-KSK Method 3.3.1. Double-KSK Method
In this rollover, The new DNSKEY is added to the zone. After an In this rollover, The new DNSKEY is added to the zone. After an
interval long enough to guarantee that any cached DNSKEY RRsets interval long enough to guarantee that any cached DNSKEY RRsets
contain the new DNSKEY, the DS record in the parent zone is changed. contain the new DNSKEY, the DS record in the parent zone is changed.
After a further interval to allow the old DS record to expire from After a further interval to allow the old DS record to expire from
caches, the old DNSKEY is removed from the zone. caches, the old DNSKEY is removed from the zone.
The timeline for a double-signature rollover is shown below. The The timeline for a Double-KSK rollover is shown below. The diagram
diagram follows the convention described in Section 3.2.1. follows the convention described in Section 3.2.1.
|0| |1| |2| |3| |4| |1| |2| |3| |4|
| | | | | | | | |
Key N | |<-Ipub->|<--->|<-Dreg->|<-----Lksk--- - - Key N |<-IpubC->|<--->|<-Dreg->|<-----Lksk--- - -
| | | | | | | | |
Key N+1 | | | | | Key N+1 | | | |
| | | | | | | | |
Key N Tgen Tpub Trdy Tsubds Tact Key N Tpub Trdy Tsbm Tact
Key N+1 Tgen Key N+1
---- Time ----> ---- Time ---->
(continued ...) (continued ...)
|5| |6| |7| |8| |9| |10| |5| |6| |7| |8| |9| |10|
| | | | | | | | | | | |
Key N - - -------------Lksk------->|<-Iret->|<----->| Key N - - --------------Lksk------->|<-Iret->|<----->|
| | | | | | | | | | | |
Key N+1 |<-Ipub->|<--->|<-Dreg->|<--------Lksk----- - - Key N+1 |<-IpubC->|<--->|<-Dreg->|<--------Lksk----- - -
| | | | | | | | | | | |
Key N Tret Tdea Trem Key N Tret Tdea Trem
Key N+1 Tpub Trdy Tsubds Tact Key N+1 Tpub Trdy Tsbm Tact
---- Time (cont) ----> ---- Time (cont) ---->
Figure 3: Timeline for a Double-Signature KSK rollover. Figure 3: Timeline for a Double-KSK rollover.
Event 0: Key N and N+1 are generated at the generate time (Tgen).
Although there is no reason why the key cannot be generated
immediately prior to its publication in the zone (Event 1), some
implementations may find it convenient to create a pool of keys in
one operation and draw from that pool as required. For this reason,
it is shown as a separate event. Keys that are available for use but
not published are said to be generated.
Event 1: Key N is introduced into the zone; it is added to the DNSKEY Event 1: Key N is introduced into the zone; it is added to the DNSKEY
RRset, which is then signed by all currently active KSKs. (So at RRset, which is then signed by all currently active KSKs. (So at
this point, the DNSKEY RRset is signed by both key N and its this point, the DNSKEY RRset is signed by both key N and its
predecessor KSK. If other KSKs were active, it is signed by these as predecessor KSK. If other KSKs were active, it is signed by these as
well.) This is the publication time of key N (Tpub); after this the well.) This is the publication time of key N (Tpub); after this the
key is said to be published. key is said to be published.
Event 2: Before it can be used, the key must be published for long Event 2: Before it can be used, the key must be published for long
enough to guarantee that any validating resolver that has a copy of enough to guarantee that any validating resolver that has a copy of
the DNSKEY RRset in its cache will have a copy of the RRset that the DNSKEY RRset in its cache will have a copy of the RRset that
includes this key: in other words, that any prior cached information includes this key: in other words, that any prior cached information
about the DNSKEY RRset has expired. about the DNSKEY RRset has expired.
The interval is the publication interval (Ipub) and, for the second The interval is the publication interval in the child zone (IpubC)
or subsequent KSKs in the zone, is given by: and is given by:
Ipub = DprpC + TTLkey IpubC = DprpC + TTLkey
... where DprpC is the propagation delay for the child zone (the zone ... where DprpC is the propagation delay for the child zone (the zone
containing the KSK being rolled) and TTLkey the TTL for the DNSKEY containing the KSK being rolled) and TTLkey the TTL for the DNSKEY
RRset. The time at which this occurs is the key N's ready time, RRset. The time at which this occurs is the key N's ready time,
Trdy, given by: Trdy, given by:
Trdy(N) = Tpub(N) + Ipub Trdy(N) = Tpub(N) + IpubC
(The case of introducing the first KSK into the zone is discussed in
Section 3.3.5.)
Event 3: At some later time, the DS record corresponding to the new Event 3: At some later time, the DS record corresponding to the new
KSK is submitted to the parent zone for publication. This time is KSK is submitted to the parent zone for publication. This time is
the submission time, Tsubds: the submission time, Tsbm:
Tsubds(N) >= Trdy(N) Tsbm(N) >= Trdy(N)
Event 4: The DS record is published in the parent zone. As this is Event 4: The DS record is published in the parent zone. As this is
the point at which all information for authentication - both DNSKEY the point at which all information for authentication - both DNSKEY
and DS record - is available in the two zones, in analogy with other and DS record - is available in the two zones, in analogy with other
rollover methods, this is called the activation time of key N (Tact): rollover methods, this is called the activation time of key N (Tact):
Tact(N) = Tsubds(N) + Dreg Tact(N) = Tsbm(N) + Dreg
... where Dreg is the registration delay, the time taken after the DS ... where Dreg is the registration delay, the time taken after the DS
record has been submitted to the parent zone manager for it to be record has been submitted to the parent zone manager for it to be
placed in the zone. (Parent zones are often managed by different placed in the zone. (Parent zones are often managed by different
entities, and this term accounts for the organisational overhead of entities, and this term accounts for the organisational overhead of
transferring a record. In practice, Dreg will not be a fixed time: transferring a record. In practice, Dreg will not be a fixed time:
instead, the end of Dreg will be signalled by the appearance of the instead, the end of Dreg will be signalled by the appearance of the
DS record in the parent zone.) DS record in the parent zone.)
Event 5: While key N is active, thought needs to be given to its Event 5: While key N is active, thought needs to be given to its
successor (key N+1). At some time before the scheduled end of the successor (key N+1). At some time before the scheduled end of the
KSK lifetime, the successor KSK is published in the zone. (As KSK lifetime, the successor KSK is published in the zone. (As
before, this means that the DNSKEY RRset is signed by all active before, this means that the DNSKEY RRset is signed by all KSKs.)
KSKs.) This time is the publication time of the successor key N+1, This time is the publication time of the successor key N+1, given by:
given by:
Tpub(N+1) <= Tact(N) + Lksk - Dreg - Ipub Tpub(N+1) <= Tact(N) + Lksk - Dreg - IpubC
... where Lksk is the actual lifetime of the KSK, and Dreg the ... where Lksk is the actual lifetime of the KSK, and Dreg the
registration delay. In practice, Dreg will not be a fixed time: registration delay.
instead, the end of Dreg will be signalled by the appearance of the
DS record in the parent zone.
Event 6: After an interval Ipub, key N+1 becomes ready (in that all Event 6: After an interval IpubC, key N+1 becomes ready (in that all
caches that have a copy of the DNSKEY RRset have a copy of this key). caches that have a copy of the DNSKEY RRset have a copy of this key).
This time is the ready time of the successor key N+1 (Trdy). This time is the ready time of the successor key N+1 (Trdy).
Event 7: At the submission time of the successor key N+1, Event 7: At the submission time of the successor key N+1, Tsbm(N+1),
Tsubds(N+1), the DS record corresponding to key N+1 is submitted to the DS record corresponding to key N+1 is submitted to the parent
the parent zone. zone.
Event 8: The successor DS record is published in the parent zone and Event 8: The successor DS record is published in the parent zone and
the current DS record withdrawn. Key N is said to be retired and the the current DS record withdrawn. Key N is said to be retired and the
time at which this occurs is Tret(N), given by: time at which this occurs is Tret(N), given by:
Tret(N) = Tsubds(N+1) + Dreg Tret(N) = Tsbm(N+1) + Dreg
Event 9: Key N must remain in the zone until any caches that contain Event 9: Key N must remain in the zone until any caches that contain
a copy of the DS RRset have a copy containing the new DS record. a copy of the DS RRset have a copy containing the new DS record.
This interval is the retire interval, given by: This interval is the retire interval, given by:
Iret = DprpP + TTLds Iret = DprpP + TTLds
... where DprpP is the propagation delay in the parent zone and TTLds ... where DprpP is the propagation delay in the parent zone and TTLds
the TTL of a DS record in the parent zone. the TTL of a DS record in the parent zone.
As the key is no longer used for anything, is said to be dead. This As the key is no longer used for anything, it is said to be dead.
point is the dead time (Tdea), given by: This point is the dead time (Tdea), given by:
Tdea(N) = Tret(N) + Iret Tdea(N) = Tret(N) + Iret
Event 10: At some later time, key N is removed from the zone's DNSKEY Event 10: At some later time, key N is removed from the zone's DNSKEY
RRset (at the remove time Trem); the key is now said to be removed. RRset (at the remove time Trem); the key is now said to be removed.
Trem(N) >= Tdea(N) Trem(N) >= Tdea(N)
3.3.2. Double-DS Method 3.3.2. Double-DS Method
In this rollover, the new DS record is published in the parent zone. In this rollover, the new DS record is published in the parent zone.
When any caches that contain the DS RRset contain a copy of the new When any caches that contain the DS RRset contain a copy of the new
record, the KSK in the zone is changed. After a further interval for record, the KSK in the zone is changed. After a further interval for
the old DNSKEY RRset to expire from caches, the old DS record is the old DNSKEY RRset to expire from caches, the old DS record is
removed from the parent. removed from the parent.
The timeline for a double-DS rollover is shown below. The diagram The timeline for a Double-DS rollover is shown below. The diagram
follows the convention described in Section 3.2.1 follows the convention described in Section 3.2.1
|0| |1| |2| |3| |4| |5| |1| |2| |3| |4| |5|
| | | | | | | | | | |
Key N | |<-Dreg->|<-IpubP->|<-->|<-------Lksk----- - - Key N |<-Dreg->|<-IpubP->|<-->|<-------Lksk----- - -
| | | | | | | | | | |
Key N+1 | | | | | |<--Dreg-- - - Key N+1 | | | | |<--Dreg-- - -
| | | | | | | | | | |
Key N Tgen Tsubds Tpub Trdy Tact Key N Tsbm Tpub Trdy Tact
Key N+1 Tgen Tsubds Key N+1 Tsbm
---- Time ----> ---- Time ---->
(continued ...) (continued ...)
|6| |7| |8| |9| |10| |6| |7| |8| |9| |10|
| | | | | | | | | |
Key N - - -----Lksk--------->|<-Iret->|<---->| Key N - - -----Lksk--------->|<-Iret->|<---->|
| | | | | | | | | |
Key N+1 - - --Dreg-->|<-IpubP->|<------>|<------Lksk------ - - Key N+1 - - --Dreg-->|<-IpubP->|<------>|<------Lksk------ - -
| | | | | | | | | |
Key N Tret Tdea Trem Key N Tret Tdea Trem
Key N+1 Tpub Trdy Tact Key N+1 Tpub Trdy Tact
---- Time ----> ---- Time ---->
Figure 4: Timeline for a Double-DS KSK rollover. Figure 4: Timeline for a Double-DS KSK rollover.
Event 0: Key N and N+1 are generated at the generate time Tgen(key).
Although there is no reason why the key cannot be generated
immediately prior to its use, some implementations may find it
convenient to create a pool of keys in one operation and draw from
that pool as required. For this reason, it is shown as a separate
event. Keys that are available for use but not published are said to
be generated.
Event 1: The DS RR is submitted to the parent zone for publication. Event 1: The DS RR is submitted to the parent zone for publication.
This time is the submission time, Tsubds. This time is the submission time, Tsbm.
Event 2: After the registration delay, Dreg, the DS record is Event 2: After the registration delay, Dreg, the DS record is
published in the parent zone. This is the publication time (Tpub) of published in the parent zone. This is the publication time (Tpub) of
key N, given by: key N, given by:
Tpub(N) = Tsubds(N) + Dreg Tpub(N) = Tsbm(N) + Dreg
As before, in practice Dreg will not be a fixed time. Instead, the
end of Dreg will be signalled by the appearance of the DS record in
the parent zone.
Event 3: At some later time, any cache that has a copy of the DS Event 3: At some later time, any cache that has a copy of the DS
RRset will have a copy of the DS record for key N. At this point, RRset will have a copy of the DS record for key N. At this point, key
key N, if introduced into the DNSKEY RRset, could be used to validate N, if introduced into the DNSKEY RRset, could be used to validate the
the zone. For this reason, this time is known as the key's ready zone. For this reason, this time is known as the ready time, Trdy,
time, Trdy, and is given by: and is given by:
Trdy(N) = Tpub(N) + IpubP Trdy(N) = Tpub(N) + IpubP
IpubP is the publication interval of the DS record and is given by IpubP is the publication interval of the DS record (in the parent
the expression: zone) and is given by the expression:
IpubP = DprpP + TTLds IpubP = DprpP + TTLds
... where DprpP is the propagation delay for the parent zone and ... where DprpP is the propagation delay for the parent zone and
TTLds the TTL assigned to DS records in that zone. TTLds the TTL assigned to DS records in that zone.
Event 4: At some later time, the key rollover takes place and the new Event 4: At some later time, the key rollover takes place and the new
key (key N) is introduced into the DNSKEY RRset and used to sign key (key N) is introduced into the DNSKEY RRset and used to sign it.
that, while the old key is removed from the DNSKEY RRset.
As both the old and new DS records have been in the parent zone long
enough to ensure that they are in caches that contain the DS RRset,
the zone can be authenticated throughout the rollover - the
validating resolver either has a copy of the DNSKEY RRset
authenticated by the predecessor key, or it has a copy of the updated
RRset authenticated with the new key.
This time is key N's activation time (Tact) and at this point key N This time is key N's activation time (Tact) and at this point key N
is said to be active: is said to be active:
Tact(N) >= Trdy(N) Tact(N) >= Trdy(N)
Event 5: At some point thought must be given to key replacement. The Event 5: At some point thought must be given to key replacement. The
DS record for the successor key must be submitted to the parent zone DS record for the successor key must be submitted to the parent zone
at a time such that when the current key is withdrawn, any cache that at a time such that when the current key is withdrawn, any cache that
contains the zone's DS records has data about the DS record of the contains the zone's DS records has data about the DS record of the
successor key. The time at which this occurs is the submission time successor key. The time at which this occurs is the submission time
of the successor key N+1, given by: of the successor key N+1, given by:
Tsubds(N+1) <= Tact(N) + Lksk - Ipub - Dreg Tsbm(N+1) <= Tact(N) + Lksk - IpubP - Dreg
... where Lksk is the actual lifetime of key N (which may differ ... where Lksk is the actual lifetime of key N (which may differ
slightly from the lifetime set in the key management policy) and Dreg slightly from the lifetime set in the key management policy) and Dreg
is the registration delay. Again, Dreg will not be a fixed time: is the registration delay.
instead, the end of Dreg will be signalled by the appearance of the
DS record in the parent zone.
Event 6. After an interval Dreg, the successor DS record is Event 6. After an interval Dreg, the successor DS record is
published in the zone at time Tpub. published in the zone.
Event 7: The successor key (key N+1) enters the ready state, i.e., Event 7: The successor key (key N+1) enters the ready state, i.e. its
its DS record is now in caches that contain the parent DS RRset. DS record is now in caches that contain the parent DS RRset.
This is the ready time of the successor key N+1, Trdy.
Event 8: When key N has been active for its lifetime (Lksk), it is Event 8: When key N has been active for its lifetime (Lksk), it is
replaced in the DNSKEY RRset by key N+1; the RRset is then signed replaced in the DNSKEY RRset by key N+1; the RRset is then signed
with the new key. This is the retire time (Tret) of key N, given by: with the new key. At this point, as both the old and new DS records
have been in the parent zone long enough to ensure that they are in
caches that contain the DS RRset, the zone can be authenticated
throughout the rollover. A validating resolver can authenticate
either the old or new KSK.
Tret(N) = Tact(N) + Lksk This time is the retire time (Tret) of key N, given by:
Tret(N) = Tact(N) + Lksk
This is also the activation time of the successor key N+1. This is also the activation time of the successor key N+1.
Event 9: At some later time, all copies of the old DNSKEY RRset have Event 9: At some later time, all copies of the old DNSKEY RRset have
expired from caches and the old DS record is no longer needed. In expired from caches and the old DS record is no longer needed. In
analogy with other rollover methods, this is called the dead time, analogy with other rollover methods, this is called the dead time,
Tdea, and is given by: Tdea, and is given by:
Tdea(N) = Tret(N) + Iret Tdea(N) = Tret(N) + Iret
... where Iret is the retire interval of the key, given by: ... where Iret is the retire interval of the key, given by:
Iret = DprpC + TTLkey Iret = DprpC + TTLkey
As before, this term includes DprpC, the time taken to propagate the As before, this term includes DprpC, the time taken to propagate the
RRset change through the master-slave hierarchy of the child zone and RRset change through the master-slave hierarchy of the child zone and
TTLkey, the time taken for the DNSKEY RRset to expire from caches. TTLkey, the time taken for the DNSKEY RRset to expire from caches.
Event 10: At some later time, the DS record is removed from the Event 10: At some later time, the DS record is removed from the
parent zone. In analogy with other rollover methods, this is the parent zone. In analogy with other rollover methods, this is the
removal time (Trem), given by: removal time (Trem), given by:
Trem(N) >= Tdea(N) Trem(N) >= Tdea(N)
3.3.3. Double-RRset Method 3.3.3. Double-RRset Method
In the double-RRset rollover, the new DNSKEY and DS records are In the Double-RRset rollover, the new DNSKEY and DS records are
published simultaneously in the appropriate zones. Once enough time published simultaneously in the appropriate zones. Once enough time
has elapsed for the old DNSKEY and DS RRsets to expire from caches, has elapsed for the old DNSKEY and DS RRsets to expire from caches,
the old DNSKEY and DS records are removed from their respective the old DNSKEY and DS records are removed from their respective
zones. zones.
The timeline for this rollover is shown below. The diagram follows The timeline for this rollover is shown below. The diagram follows
the convention described in Section 3.2.1 the convention described in Section 3.2.1
|0| |1| |2| |3| |4| |5|
| | | | | | |1| |2| |3| |4| |5|
Key N | |<-Ipub->|<-----Lksk----->|<------>| | | | | |
| | | | | | Key N |<-Ipub->|<-----Lksk----->|<------>|
Key N+1 | | | |<-Ipub->|<------Lksk--- - - | | | | |
| | | | | | Key N+1 | | |<-Ipub->|<------Lksk--- - -
Key N Tgen Tpub Tact Tret Trem | | | | |
Key N+1 Tgen Tpub Tact Key N Tpub Tact Tret Trem
Key N+1 Tpub Tact
---- Time ----> ---- Time ---->
Figure 5: Timeline for a Double-RRset KSK rollover. Figure 5: Timeline for a Double-RRset KSK rollover.
Event 0: Key N and N+1 are generated at the generate time (Tgen).
Although there is no reason why the key cannot be generated
immediately prior to its publication in the zone (Event 1), some
implementations may find it convenient to create a pool of keys in
one operation and draw from that pool as required. For this reason,
it is shown as a separate event. Keys that are available for use but
not published are said to be generated.
Event 1: The key is added to and used for signing the DNSKEY RRset Event 1: The key is added to and used for signing the DNSKEY RRset
and is thereby published in the zone. At the same time the and is thereby published in the zone. At the same time the
corresponding DS record is submitted to the parent zone for corresponding DS record is submitted to the parent zone for
publication. This time is the publish time for key N (Tpub) and the publication. This time is the publish time for key N (Tpub) and the
key is said to be published. key is said to be published.
Event 2: At some later time, the DS record is published in the parent Event 2: At some later time, the DS record is published in the parent
zone and at some time after that, the updated information has reached zone and at some time after that, the updated information has reached
all caches: any cache that holds a DNSKEY RRset from the child zone all caches: any cache that holds a DNSKEY RRset from the child zone
will have a copy that includes the new KSK, and any cache that has a will have a copy that includes the new KSK, and any cache that has a
copy of the parent DS RRset will have a copy that includes the new DS copy of the parent DS RRset will have a copy that includes the new DS
record. record.
The time at which this occurs is called the activation time of key N The time at which this occurs is called the activation time of key N
(Tact), given by: (Tact), given by:
Tact(N) = Tpub(N) + Ipub Tact(N) = Tpub(N) + Ipub
... where Ipub is the composite publication interval for the DNSKEY ... where Ipub is the composite publication interval for the DNSKEY
and DS records, given by: and DS records, given by:
Ipub = max(IpubP, IpubC), Ipub = max(IpubP, IpubC),
IpubP being the publication interval of the DS record in the parent IpubP being the publication interval of the DS record in the parent
zone and IpubC the publication interval of the DNSKEY in the child zone and IpubC the publication interval of the DNSKEY in the child
zone. The parent zone's publication interval is given by: zone. The parent zone's publication interval is given by:
IpubP = Dreg + DprpP + TTLds IpubP = Dreg + DprpP + TTLds
where Dreg is the registration delay, the time taken for the DS where Dreg is the registration delay, the time taken for the DS
record to be published in the parent zone. DprpP is the parent record to be published in the parent zone. DprpP is the parent
zone's propagation delay and TTLds is the TTL of the DS record in zone's propagation delay and TTLds is the TTL of the DS record in
that zone. that zone.
The child zone's publication interval is given by a similar equation: The child zone's publication interval is given by a similar equation:
IpubC = DprpC + TTLkey IpubC = DprpC + TTLkey
... where DprpC is the propagation delay in the child zone and TTLkey ... where DprpC is the propagation delay in the child zone and TTLkey
the TTL of a DNSKEY record. the TTL of a DNSKEY record.
Event 3: At some point we need to give thought to key replacement. Event 3: At some point we need to give thought to key replacement.
The successor key (key N+1) must be introduced into the zone (and its The successor key (key N+1) must be introduced into the zone (and its
DS record submitted to the parent) at a time such that it becomes DS record submitted to the parent) at a time such that it becomes
active when the current key has been active for its actual lifetime, active when the current key has been active for its actual lifetime,
Lksk. This is the publication time (Tpub) of the successor key, and Lksk. This is the publication time (Tpub) of the successor key, and
is given by: is given by:
Tpub(N+1) <= Tact(N) + Lksk - Ipub Tpub(N+1) <= Tact(N) + Lksk - Ipub
... where Lksk is the actual lifetime of the KSK and Ipub is as ... where Lksk is the actual lifetime of the KSK and Ipub is as
defined above. defined above.
Event 4: Key N+1's DNSKEY and DS records are now in caches that Event 4: Key N+1's DNSKEY and DS records are now in caches that
contain the child zone DNSKEY and/or the parent zone DS RR, and so contain the child zone DNSKEY and/or the parent zone DS RR, and so
the zone can be validated with the new key. This is the activation the zone can be validated with the new key. This is the activation
time (Tact) of the successor key N+1 and by analogy with other time (Tact) of the successor key N+1 and by analogy with other
rollover methods, it is also the dead time of key N: rollover methods, it is also the dead time of key N:
Tdea(N) = Tact(N) + Lksk Tdea(N) = Tact(N) + Lksk
Event 5: At some later time, the key N's DS and DNSKEY records are Event 5: At some later time, the key N's DS and DNSKEY records are
removed from their respective zones. In analogy with other rollover removed from their respective zones. In analogy with other rollover
methods, this is the removal time (Trem), given by: methods, this is the removal time (Trem), given by:
Trem(N) >= Tdea(N) Trem(N) >= Tdea(N)
3.3.4. Interaction with Configured Trust Anchors 3.3.4. Interaction with Configured Trust Anchors
Although the preceding sections have been concerned with rolling KSKs Although the preceding sections have been concerned with rolling KSKs
where the trust anchor is a DS record in the parent zone, zone where the trust anchor is a DS record in the parent zone, zone
managers may want to take account of the possibility that some managers may want to take account of the possibility that some
validating resolvers may have configured trust anchors directly. validating resolvers may have configured trust anchors directly.
Rolling a configured trust anchor is dealt with in [RFC5011]. It Rolling a configured trust anchor is dealt with in [RFC5011]. It
requires introducing the KSK to be used as the trust anchor into the requires introducing the KSK to be used as the trust anchor into the
zone for a period of time before use, and retaining it (with the zone for a period of time before use, and retaining it (with the
"revoke" bit set) for some time after use. "revoke" bit set) for some time after use.
3.3.4.1. Addition of KSK 3.3.4.1. Addition of KSK
When the new key is introduced, the publication interval (Ipub) in When the new key is introduced, the expression for the publication
the Double-Signature and Double-RRset methods should also be subject interval of the DNSKEY(IpubC) in the Double-KSK and Double-RRset
to the condition: methods is modified to:
Ipub >= Dprp + max(Itrp, TTLkey) IpubC >= DprpC + max(Itrp, TTLkey)
... where the right hand side of the expression is the time taken for ... where the right hand side of the expression now includes the
the change to propagate to all nameservers for the zone plus the "trust point" interval. This term is the interval required to
"trust point" interval. This latter term is the interval required to
guarantee that a resolver configured for the automatic update of keys guarantee that a resolver configured for the automatic update of keys
from a particular trust point will see at least two validated DNSKEY from a particular trust point will see at least two validated DNSKEY
RRsets containing the new key (a requirement from [RFC5011], section RRsets containing the new key (a requirement from [RFC5011], section
2.4.1). It is defined by the expression: 2.4.1). It is defined by the expression:
Itrp >= (2 * queryInterval) + (n * retryTime) Itrp >= (2 * queryInterval) + (n * retryTime)
... where queryInterval and retryTime are as defined in section 2.3 ... where queryInterval and retryTime are as defined in section 2.3
of [RFC5011]. "n" is the total number of retries needed by the of [RFC5011]. "n" is the total number of retries needed by the
resolver during the two attempts to get the DNSKEY RRset. resolver during the two attempts to get the DNSKEY RRset.
The first term of the expression (2 * queryInterval) represents the The first term of the expression (2 * queryInterval) represents the
time to obtain two validated DNSKEY RRsets. The second term (n * time to obtain two validated DNSKEY RRsets. The second term (n *
retryTime) is a safety margin, with the value of "n" reflecting the retryTime) is a safety margin, with the value of "n" reflecting the
degree of confidence in the communication between a resolver and the degree of confidence in the communication between a resolver and the
trust point. trust point.
In the Double-DS method, instead of swapping the KSK RRs in a single In the Double-DS method, instead of swapping the KSK RRs in a single
step, there must now be a period of overlap. In other words, the new step, there must now be a period of overlap. In other words, the new
KSK must be introduced into the zone at least: KSK must be introduced into the zone at least:
DprpC + max(Itrp, TTLkey) DprpC + max(Itrp, TTLkey)
... before the switch is made. ... before the switch is made.
3.3.4.2. Removal of KSK 3.3.4.2. Removal of KSK
The timeline for the removal of the key in all methods is modified by The timeline for the removal of the key in all methods is modified by
introducing a new state, "revoked". When the key reaches its dead introducing a new state, "revoked". When the key reaches its dead
time, instead of being declared "dead", it is revoked; the "revoke" time, instead of being declared "dead", it is revoked; the "revoke"
bit is set in the published DNSKEY RR, and the DNSKEY RRset re-signed bit is set in the published DNSKEY RR, and the DNSKEY RRset re-signed
with the current and revoked keys. The key is maintained in this with the current and revoked keys. The key is maintained in this
state for the "revoke" interval, Irev, given by: state for the "revoke" interval, Irev, given by:
Irev >= 30 days Irev >= 30 days
... 30 days being the [RFC5011] remove hold-down time. After this ... 30 days being the [RFC5011] remove hold-down time. After this
time, the key is dead and can be removed from the zone. time, the key is dead and can be removed from the zone.
3.3.5. Introduction of First Keys 3.3.5. Introduction of First Keys
There are no timing considerations associated with the introduction There are no timing considerations associated with the introduction
of the first keys into a zone other that they must be introduced and of the first keys into a zone other that they must be introduced and
the zone validly signed before a chain of trust to the zone is the zone validly signed before a chain of trust to the zone is
created. created.
This is important: in the case of a secure parent, it means ensuring This is important: in the case of a secure parent, it means ensuring
that the DS record is not published in the parent zone until there is that the DS record is not published in the parent zone until there is
no possibility that a validating resolver can obtain the record yet no possibility that a validating resolver can obtain the record yet
is not able to obtain the corresponding DNSKEY. In the case of an is not able to obtain the corresponding DNSKEY. In the case of an
insecure parent, i.e., the initial creation of a new security apex, insecure parent, i.e. the initial creation of a new security apex, it
it is not possible to guarantee this. It is up to the operator of is not possible to guarantee this. It is up to the operator of the
the validating resolver to wait for the new KSK to appear at all validating resolver to wait for the new KSK to appear at all servers
servers for the zone before configuring the trust anchor. for the zone before configuring the trust anchor.
4. Standby Keys 4. Standby Keys
Although keys will usually be rolled according to some regular Although keys will usually be rolled according to some regular
schedule, there may be occasions when an emergency rollover is schedule, there may be occasions when an emergency rollover is
required, e.g., if the active key is suspected of being compromised. required, e.g., if the active key is suspected of being compromised.
The aim of the emergency rollover is to allow the zone to be re- The aim of the emergency rollover is to allow the zone to be re-
signed with a new key as soon as possible. As a key must be in the signed with a new key as soon as possible. As a key must be in the
ready state to sign the zone, having at least one additional key (a ready state to sign the zone, having at least one additional key (a
standby key) in this state at all times will minimise delay. standby key) in this state at all times will minimise delay.
skipping to change at page 24, line 4 skipping to change at page 23, line 22
included in the zone or successor keys could be introduced as soon as included in the zone or successor keys could be introduced as soon as
possible after a key becomes active. Either way results in one or possible after a key becomes active. Either way results in one or
more additional ZSKs in the DNSKEY RRset that can immediately be used more additional ZSKs in the DNSKEY RRset that can immediately be used
to sign the zone if the current key is compromised. to sign the zone if the current key is compromised.
(Although in theory the mechanism could be used with both the Double- (Although in theory the mechanism could be used with both the Double-
Signature and Double-RRSIG methods, it would require pre-publication Signature and Double-RRSIG methods, it would require pre-publication
of the signatures. Essentially, the standby key would be permanently of the signatures. Essentially, the standby key would be permanently
active, as it would have to be periodically used to renew signatures. active, as it would have to be periodically used to renew signatures.
Zones would also permanently require two sets of signatures.) Zones would also permanently require two sets of signatures.)
It is also possible to have a standby KSK. The Double-Signature
method requires that the standby KSK be included in the DNSKEY RRset; It is also possible to have a standby KSK. The Double-KSK method
requires that the standby KSK be included in the DNSKEY RRset;
rolling the key then requires just the introduction of the DS record rolling the key then requires just the introduction of the DS record
in the parent. Note that the standby KSK should also be used to sign in the parent. Note that the standby KSK should also be used to sign
the DNSKEY RRset. As the RRset and its signatures travel together, the DNSKEY RRset. As the RRset and its signatures travel together,
merely adding the KSK without using it to sign the DNSKEY RRset does merely adding the KSK without using it to sign the DNSKEY RRset does
not provide the desired time saving: for a KSK to be used in a not provide the desired time saving: for a KSK to be used in a
rollover the DNSKEY RRset must be signed with it, and this would rollover the DNSKEY RRset must be signed with it, and this would
introduce a delay while the old RRset (not signed with the new key) introduce a delay while the old RRset (not signed with the new key)
expires from caches. expires from caches.
The idea of a standby KSK in the Double-RRset rollover method The idea of a standby KSK in the Double-RRset rollover method
skipping to change at page 25, line 5 skipping to change at page 24, line 25
6. Limitation of Scope 6. Limitation of Scope
This document represents current thinking at the time of publication. This document represents current thinking at the time of publication.
However, the subject matter is evolving and it is more than likely However, the subject matter is evolving and it is more than likely
that this document will need to be revised in the future. that this document will need to be revised in the future.
Some of the techniques and ideas that DNSSEC operators are Some of the techniques and ideas that DNSSEC operators are
considering differ from this those described in this document. Of considering differ from this those described in this document. Of
particular interest are alternatives to the strict split into KSK and particular interest are alternatives to the strict split into KSK and
ZSK key roles and the consequences for rollover logic from partial ZSK key roles and the consequences for rollover logic from partial
signing (i.e., when the new key initially only signs a fraction of signing (i.e. when the new key initially only signs a fraction of the
the zone while leaving other signatures generated by the old key in zone while leaving other signatures generated by the old key in
place). place).
Furthermore, as noted in section 5, this document covers only rolling Furthermore, as noted in section 5, this document covers only rolling
keys of the same algorithm: it does not cover transitions between keys of the same algorithm: it does not cover transitions between
algorithms. The timing issues associated with algorithm rollovers algorithms. The timing issues associated with algorithm rollovers
will require a separate document. will require a separate document.
The reader is therefore reminded that DNSSEC is, as of date of The reader is therefore reminded that DNSSEC is, as of date of
publication, in the early stages of deployment, and best practices publication, in the early stages of deployment, and best practices
may further develop over time. may further develop over time.
skipping to change at page 26, line 13 skipping to change at page 25, line 31
already discussed in [RFC4033], [RFC4034], [RFC4035] and [RFC5011]. already discussed in [RFC4033], [RFC4034], [RFC4035] and [RFC5011].
10. Acknowledgements 10. Acknowledgements
The authors gratefully acknowledge help and contributions from Roy The authors gratefully acknowledge help and contributions from Roy
Arends and Wouter Wijngaards. Arends and Wouter Wijngaards.
11. Normative References 11. Normative References
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", RFC Rose, "DNS Security Introduction and Requirements",
4033, March 2005. RFC 4033, March 2005.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions", Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, March 2005. RFC 4034, March 2005.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, March 2005. Extensions", RFC 4035, March 2005.
[RFC5011] StJohns, M., "Automated Updates of DNS Security (DNSSEC) [RFC5011] StJohns, M., "Automated Updates of DNS Security (DNSSEC)
Trust Anchors", STD 74, RFC 5011, September 2007. Trust Anchors", STD 74, RFC 5011, September 2007.
[RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC [RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC
Operational Practices, Version 2", RFC 6781, December Operational Practices, Version 2", RFC 6781,
2012. December 2012.
Appendix A. List of Symbols Appendix A. List of Symbols
The document defines a number of symbols, all of which are listed The document defines a number of symbols, all of which are listed
here. All are of the form: here. All are of the form:
All symbols used in the text are of the form: All symbols used in the text are of the form:
<TYPE><id><INST> <TYPE><id><ZONE>
where: where:
<TYPE> is an upper-case character indicating what type the symbol is. <TYPE> is an upper-case character indicating what type the symbol is.
Defined types are: Defined types are:
D delay: interval that is a feature of the process D delay: interval that is a feature of the process
I interval between two events I interval between two events
skipping to change at page 27, line 4 skipping to change at page 26, line 26
<TYPE> is an upper-case character indicating what type the symbol is. <TYPE> is an upper-case character indicating what type the symbol is.
Defined types are: Defined types are:
D delay: interval that is a feature of the process D delay: interval that is a feature of the process
I interval between two events I interval between two events
L lifetime: interval set by the zone manager L lifetime: interval set by the zone manager
T a point in time T a point in time
TTL TTL of a record TTL TTL of a record
I and T and TTL are self-explanatory. Like I, both D and L are time I, T and TTL are self-explanatory. Like I, both D and L are time
periods, but whereas I values are intervals between two events (even periods, but whereas I values are intervals between two events (even
if the events are defined in terms of the interval, e.g., the dead if the events are defined in terms of the interval, e.g., the dead
time occurs "retire interval" after the retire time), D and L are time occurs "retire interval" after the retire time), D and L are
fixed intervals: a "D" interval (delay) is a feature of the process, fixed intervals: a "D" interval (delay) is a feature of the process,
probably outside control of the zone manager, whereas an "L" interval probably outside control of the zone manager, whereas an "L" interval
(lifetime) is chosen by the zone manager and is a feature of policy. (lifetime) is chosen by the zone manager and is a feature of policy.
<id> is lower-case and defines what object or event the variable is <id> is lower-case and defines what object or event the variable is
related to, e.g., related to, e.g.,
act activation act activation
pub publication pub publication
ret retire ret retire
<INST> is a capital letter that distinguishes between the same <ZONE> is an optional capital letter that distinguishes between the
variable applying to different instances of an object and is one of: same variable applied to different zones and is one of:
C child C child
P parent P parent
Within the rollover descriptions, times are suffixed the a number in Within the rollover descriptions, times may be suffixed by a number
brackets indicating the the key to which they apply, e.g. Tact(N) is in brackets indicating the instance of the key to which they apply,
the activation time of key N, Tpub(N+1) the publication time of key e.g. Tact(N) is the activation time of key N, Tpub(N+1) the
N+1 etc. publication time of key N+1 etc.
The list of variables used in the text given below. The list of variables used in the text given below.
Dprp Propagation delay. The amount of time for a change made at Dprp Propagation delay. The amount of time for a change made at
a master nameserver to propagate to all the slave a master nameserver to propagate to all the slave
nameservers. nameservers.
DprpC Propagation delay in the child zone. DprpC Propagation delay in the child zone.
DprpP Propagation delay in the parent zone. DprpP Propagation delay in the parent zone.
Dreg Registration delay: the time taken for a DS record Dreg Registration delay: the time taken for a DS record
submitted to a parent zone to appear in it. As a parent submitted to a parent zone to appear in it. As a parent
zone is often managed by a different organisation to that zone is often managed by a different organisation to that
managing the child zone, the delays associated with passing managing the child zone, the delays associated with passing
data between zones is captured by this term. data between organisations is captured by this term.
Dsgn Signing delay. After the introduction of a new ZSK, the Dsgn Signing delay. After the introduction of a new ZSK, the
amount of time taken for all the RRs in the zone to be amount of time taken for all the RRs in the zone to be
signed with it. signed with it.
Ipub Publication interval. The amount of time that must elapse Ipub Publication interval. The amount of time that must elapse
after the publication of a record before it can be assumed after the publication of a DNSKEY and/or its associated
that any resolvers that have the relevant RRset cached have data before it can be assumed that any resolvers that have
a copy of the new information. the relevant RRset cached have a copy of the new
information.
IpubC Publication interval in the child zone. IpubC Publication interval in the child zone.
IpubP Publication interval in the parent zone. IpubP Publication interval in the parent zone.
Iret Retire interval. The amount of time that must elapse after Iret Retire interval. The amount of time that must elapse after
a DNSKEY or DS record enters the retire state for any a DNSKEY or associated data enters the retire state for any
dependent information (e.g. RRSIG for a DNSKEY) to be dependent information (e.g. RRSIG for a ZSK) to be purged
purged from validating resolver caches. from validating resolver caches.
Irev Revoke interval. The amount of time that a KSK must remain Irev Revoke interval. The amount of time that a KSK must remain
published with the revoke bit set to satisfy [RFC5011] published with the revoke bit set to satisfy [RFC5011]
considerations. considerations.
Itrp Trust-point interval. The amount of time that a trust Itrp Trust-point interval. The amount of time that a trust
anchor must be published for to guarantee that a resolver anchor must be published for to guarantee that a resolver
configured for an automatic update of keys will see the new configured for an automatic update of keys will see the new
key at least twice. key at least twice.
skipping to change at page 28, line 44 skipping to change at page 28, line 22
active KSK. Depending on when the key is rolled-over, the active KSK. Depending on when the key is rolled-over, the
actual lifetime may be longer or shorter than the intended actual lifetime may be longer or shorter than the intended
key lifetime indicated by management policy. key lifetime indicated by management policy.
Lzsk Lifetime of a zone-signing key. This is the actual amount Lzsk Lifetime of a zone-signing key. This is the actual amount
of time for which the ZSK is used to sign the zone. of time for which the ZSK is used to sign the zone.
Depending on when the key is rolled-over, the actual Depending on when the key is rolled-over, the actual
lifetime may be longer or shorter than the intended key lifetime may be longer or shorter than the intended key
lifetime indicated by management policy. lifetime indicated by management policy.
Tact Activation time of the rollover; the time at which the key Tact Activation time. The time at which the key is regarded as
is regarded as the principal key for the zone. the principal key for the zone.
Tdea Dead time of a key. Applicable only to ZSKs, this is the
time at which any record signatures held in validating
resolver caches are guaranteed to be created with the
successor key.
Tgen Generation time of a rollover. The time that a key is Tdea Dead time. The time at which any information held in
created. validating resolver caches is guaranteed to contain
information related to the successor key. At this point,
the current key and its associated information are not
longed required for validation purposes.
Tpub Publication time of a rollover. The time that information Tpub Publication time. The time that the key or associated data
such as the DNSKEY or DS record appears in the zone for the appears in the zone for the first time.
first time.
Trem Removal time of a rollover. The time at which information Trem Removal time. The time at which the key and its associated
is removed from the zone. information starts being removed from their respective
zones.
Tret Retire time of a rollover. The time at which successor Tret Retire time. The time at which successor information
information starts being used. starts being used.
Trdy Ready time of a rollover. The time at which it can be Trdy Ready time. The time at which it can be guaranteed that
guaranteed that validating resolvers that have information validating resolvers that have information about the key
from this zone cached have a copy of the new information in and/or associated data cached have a copy of the new
their cache. (In the case of KSKs, should the validating information.
resolvers also have DS information from the parent zone
cached, the cache must include information about the DS
record corresponding to the key.)
Tsubds Submission time. The time at which the DS record of a KSK Tsbm Submission time. The time at which the DS record of a KSK
is submitted to the parent zone. is submitted to the parent zone.
TTLds Time to live of a DS record. TTLds Time to live of a DS record.
TTLkey Time to live of a DNSKEY record. (By implication, this is TTLkey Time to live of a DNSKEY record. (By implication, this is
also the time to live of the signatures on the DNSKEY also the time to live of the signatures on the DNSKEY
RRset.) RRset.)
TTLsig The maximum time to live of all the RRSIG records in the TTLsig The maximum time to live of all the RRSIG records in the
zone that were created with the ZSK. zone that were created with the ZSK.
Appendix B. Change History (To be removed on publication) Appendix B. Change History (To be removed on publication)
o draft-ietf-dnsop-dnssec-key-timing-05
* Some more renamings of "Double-Signature" KSK rollover to
"Double-KSK".
* Remove Tgen from diagrams.
* Review by Richard Lamb.
* Updated KSK rollover summary text.
* Updated variable descriptions in the appendix.
o draft-ietf-dnsop-dnssec-key-timing-04 o draft-ietf-dnsop-dnssec-key-timing-04
* Renamed to "DNSSEC Key Rollover Timing Considerations" to * Renamed to "DNSSEC Key Rollover Timing Considerations" to
emphasise that this draft concerns rollover timings. emphasise that this draft concerns rollover timings.
* Updated 4641bis reference to RFC 6781. * Updated 4641bis reference to RFC 6781.
* Add introductory paragraph to each rollover description * Add introductory paragraph to each rollover description
summarising its essential features. summarising its essential features.
* Remove detailed description of double-RRSIG ZSK rollover. It is * Remove detailed description of double-RRSIG ZSK rollover. It is
extremely unlikely to be used in any practical situation. extremely unlikely to be used in any practical situation.
* "Double-Signature" KSK rollover renamed to "Double-KSK" to avoid * "Double-Signature" KSK rollover renamed to "Double-KSK" to avoid
confusion with the ZSK rollover of the same name. confusion with the ZSK rollover of the same name.
skipping to change at page 31, line 38 skipping to change at page 31, line 22
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 End of changes. 124 change blocks. 
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