wdiff draft-ietf-dnsop-rfc5011-security-considerations-02.txt draft-ietf-dnsop-rfc5011-security-considerations-03.txt

dnsop W. Hardaker
Internet-Draft USC/ISI
Updates: 7583 (if approved) W. Kumari
Intended status: Standards Track W. Kumari
Expires: December 29, 2017 Google
June 27,
Expires: March 16, 2018 September 12, 2017

Security Considerations for RFC5011 Publishers
draft-ietf-dnsop-rfc5011-security-considerations-02
draft-ietf-dnsop-rfc5011-security-considerations-03

Abstract

This document extends the RFC5011 rollover strategy with timing
advice that must be followed in order to maintain security.
Specifically, this document describes the math behind the minimum
time-length that a DNS zone publisher must wait before signing
exclusively with
only recently added DNSKEYs. This document also
describes the minimum time-length that a DNS zone publisher must wait
after publishing a revoked DNSKEY before assuming that all active
RFC5011 resolvers should have seen the revocation-marked key and
removed it from their list of trust anchors.

Status of This Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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This Internet-Draft will expire on December 29, 2017. March 16, 2018.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Document History and Motivation . . . . . . . . . . . . . 3
1.2. Safely Rolling the Root Zone's KSK in 2017/2018 . . . . . 3
1.3. Requirements notation . . . . . . . . . . . . . . . . . . 3
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Timing Associated with RFC5011 Processing . . . . . . . . . . 4
4.1. Timing Associated with Publication . . . . . . . . . . . 4
4.2. Timing Associated with Revocation . . . . . . . . . . . . 5
5. Denial of Service Attack Considerations . . . . . . . . . . . 5
5.1. Enumerated Attack Example . . . . . . . . . . . . . . . . 5
5.1.1. Attack Timing Breakdown . . . . . . . . . . . . . . . 6
6. Minimum RFC5011 Timing Requirements . . . . . . . . . . . . . 7 8
6.1. Timing Requirements For Adding a New KSK . . . . . . . . 8
6.1.1. Example Results . . . . . . . . . . . . . . . . . . . 10
6.2. Timing Requirements For Revoking an Old KSK . . . . . . . 10
6.2.1. Example Results . . . . . . . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 11
8. Operational Considerations . . . . . . . . . . . . . . . . . 9 11
9. Security Considerations . . . . . . . . . . . . . . . . . . . 9 11
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 12
11. Normative References . . . . . . . . . . . . . . . . . . . . 10 12
Appendix A. Real World Example: The 2017 Root KSK Key Roll . . . 10
Appendix B. Changes / Author Notes. . . . . . . . . . . . . . . 11 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 13

1. Introduction

[RFC5011] defines a mechanism by which DNSSEC validators can extend update
their list of trust anchors when they've seen a new key published in
a zone. However, RFC5011 [intentionally] provides no guidance to the
publishers of DNSKEYs about how long they must wait before switching
to exclusively using only recently published keys for signing records, or
how long they must wait before removing ceasing publication of a revoked key from a zone. key.
Because of this lack of guidance, zone publishers may derive
incorrect assumptions about safe usage of the RFC5011 DNSKEY
advertising, rolling and revocation process. This document describes
the minimum security requirements from a publisher's point of view
and is intended to compliment complement the guidance offered in RFC5011 (which
is written to provide timing guidance solely to a Validating
Resolver's point of view).

1.1. Document History and Motivation

To verify this lack of understanding is wide-spread, the authors
reached out to 5 DNSSEC experts to ask them how long they thought
they must wait before signing a zone using exclusively with a new KSK
[RFC4033] that was being rolled introduced according to the 5011 process.
All 5 experts answered with an insecure value, and we determined that
this lack of operational guidance is causing security concerns today
and wrote this companion document to RFC5011. We hope that this
document will rectify this understanding and provide better guidance
to zone publishers that wish to make use of the RFC5011 rollover
process.

1.2. Safely Rolling the Root Zone's KSK in 2017/2018

One important note about ICANN's [currently upcoming] 2017/2018 KSK
rollover plan for the root zone: the timing values chosen for rolling
the KSK in the root zone appear completely safe, and are not affected
by the timing concerns introduced by this draft

1.3. Requirements notation

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].

2. Background

The RFC5011 process describes a process by which a RFC5011 Validating
Resolver may accept a newly published KSK as a trust anchor for
validating future DNSSEC signed records. It also describes the
process for publicly revoking a published KSK. This document
augments that information with additional constraints, as required from the
DNSKEY publication and revocation's points of view. Note that it this
document does not define any other operational guidance or
recommendations about the RFC5011 process and restricts itself to
solely the security and operational ramifications of switching to
exclusively using only recently added keys or removing a revoked keys too
soon.

Failure of a DNSKEY publisher to follow the minimum recommendations
associated with this draft will result in potential denial-of-service
attack opportunities against validating resolvers. Failure of a
DNSKEY publisher to publish a revoked key for a long enough period of
time may result in RFC5011 Validating Resolvers leaving a that key in
their trust anchor storage beyond their the key's expected lifetime.

3. Terminology

Trust Anchor Publisher The entity responsible for publishing a
DNSKEY that can be used as a trust anchor.

Zone Signer The owner of a zone intending to publish a new Key-
Signing-Key (KSK) that will become a trust anchor by validators
following the RFC5011 process.

RFC5011 Validating Resolver A DNSSEC Validating Resolver that is
using the RFC5011 processes to track and update trust anchors.
Sometimes referred to as a "RFC5011 Resolver"

Attacker An attacker entity intent on foiling the RFC5011 Validator's ability
to successfully adopt the Zone Signer's new DNSKEY as a new trust
anchor or to prevent the RFC5011 Validator from removing an old
DNSKEY from its list of trust anchors.

SigExpirationTime The amount of time remaining before a RRSIG's
Signature Expiration time is reached. This will fundamentally be
the RRSIG's Signature Expiration time minus the RRSIG's Signature
Inception time when the signature is created.

Also see Section 2 of [RFC4033] and [RFC7719] for additional
terminology.

4. Timing Associated with RFC5011 Processing

These sections define a high-level overview of [RFC5011] processing.
These steps are not sufficient for proper RFC5011 implementation, but
provide enough background for the reader to follow the discussion in
this document. Readers need to fully understand [RFC5011] as well to
fully comprehend the importance of this document.

4.1. Timing Associated with Publication

RFC5011's process of safely publishing a new key and then making use
of that key falls into a number of high-level steps to be performed
by the Trust Anchor Publisher: Publisher. This document discusses the following
scenario, which is one of many possible combinations of operations
defined in Section 6 of RFC5011:

1. Publish a new DNSKEY in the zone, but continue to sign the zone
with the old one.

2. Wait a period of time.

3. Begin using only to exclusively use recently published DNSKEYs to sign the
appropriate resource records.

This document discusses step 2 of the above process. Some
interpretations of RFC5011 have erroneously determined that the wait
time is equal to RFC5011's "hold down time". Section 5 describes an
attack based on this (common) erroneous belief, which results can result in a
denial of service attack against the zone
if that value is used. zone.

4.2. Timing Associated with Revocation

RFC5011's process of advertising that an old key is to be revoked
from RFC5011 validating resolvers falls into a number of high-level
steps:

1. Set the revoke bit on the DNSKEY to be revoked.

2. Sign the revoked DNSKEY with itself.

3. Wait a period of time.

4. Remove the revoked key from the zone.

This document discusses step 3 of the above process. Some
interpretations of RFC5011 have erroneously determined that the wait
time is equal to RFC5011's "hold down time". This document describes
an attack based on this (common) erroneous belief, which results in a
revoked DNSKEY potentially staying remaining as a trust anchor in a RFC5011
validating resolver long past its expected usage.

5. Denial of Service Attack Considerations

If an attacker is able to provide a RFC5011 Validating Resolver with
past responses, such as when it is in-path or able to otherwise perform any
number of cache poisoning attacks, the attacker may be able to leave
compliant RFC5011-Validating Resolvers without an appropriate DNSKEY
trust anchor. This scenario will remain until an administrator
manually fixes the situation.

The following timeline time-line below illustrates this situation.

5.1. Enumerated Attack Example

The following example settings are used in the example scenario
within this section:

TTL (all records) 1 day

DNSKEY RRSIG Signature Validity
SigExpirationTime 10 days

Zone resigned every 1 day

Given these settings, the sequence of events in Section 5.1.1 depicts
how a Trust Anchor Publisher that waits for only the RFC5011 hold
time timer length of 30 days subjects its users to a potential Denial
of Service attack. The timing schedule listed below is based on a
Trust Anchor Publisher publishing a new Key Signing Key (KSK), with
the intent that it will later become a trust anchor. We label this
publication time as "T+0". All numbers in this sequence refer to
days before and after this initial publication event. Thus, T-1 is
the day before the introduction of the new key, and T+15 is the 15th
day after the key was introduced into the fictitious zone being
discussed.

In this dialog, we consider two keys being published: within the example zone:

K_old An older KSK and Trust Anchor being replaced.

K_new A new KSK being transitioned into active use and becoming expected to
become a Trust Anchor via the RFC5011 process.

5.1.1. Attack Timing Breakdown

The following series of steps depicts the timeline in which shows an attack
occurs that foils the adoption of a new DNSKEY by
a 5011 Validating Resolver when the Trust Anchor Publisher that
starts signing and publishing with the new DNSKEY too quickly.

T-1 The last K_old based RRSIGs are being published by the Zone Signer that signs only
K_old key using the K_old key itself. Signer.
[It may also be signing ZSKs as well, but they are not relevant to
this event so we will not talk further about them; we are only talking about
considering the RRSIGs that cover the DNSKEYs.] DNSKEYs in this document.]
The Attacker queries for, retrieves and caches this DNSKEY set and
corresponding RRSIG signatures.

T-0

T+0 The Zone Signer adds K_new to their zone and signs the zone's
key set with K_old. The RFC5011 Validator (later to be under
attack) retrieves this new key set and corresponding RRSIGs and
notices the publication of K_new. The RFC5011 Validator starts
the (30-day) hold-down timer for K_new. [Note that in a more
real-world scenario there will likely be a further delay between
the point where the Zone Signer publishes a new RRSIG and the
RFC5011 Validator notices its publication; though not shown in
this example, this delay is accounted for in the final solution
below]

T+5 The RFC5011 Validator queries for the zone's keyset per the
RFC5011 Active Refresh schedule, discussed in Section 2.3 of
RFC5011. Instead of receiving the intended published keyset, the
Attacker successfully replays the keyset and associated signatures
that they
recorded at T-1. Because the signature lifetime is 10 days (in
this example), the replayed signature and keyset is accepted as
valid (being only 6 days old) old, which is less than
SigExpirationTime) and the RFC5011 Validator cancels the hold-down
timer for K_new, per the RFC5011 algorithm.

T+10 The RFC5011 Validator queries for the zone's keyset and
discovers the new kset which a signed keyset that includes K_new (again), and is
signed by K_old. Note: the attacker is unable to replay the
records cached at T-1, because they have now expired. The Thus at
T+10, the RFC5011 Validator starts (anew) the hold-timer for
K_new.

T+15,T+20, and T+25

T+11 through T-29 The RFC5011 Validator continues checking the
zone's key set at the prescribed regular intervals. The RFC5011
Validator's hold-down timer keep running without being reset
assuming all of the validations succeed (again: During this
period, the attacker can no longer replay traffic to their benefit).
benefit.

T+30 The Zone Signer knows that this is the first time at which some
validators might accept K_new as a new trust anchor, since the
hold-down timer of a RFC5011 Validator not under attack that had
queried and retrieved K_new at T+0 would now have reached 30 days.
However, the hold-down timer of our attacked RFC5011 Validator is
only at 20 days.

T+35 The Zone Signer (mistakenly) believes that all validators
following the Active Refresh schedule (Section 2.3 of RFC5011)
should have accepted K_new as a the new trust anchor (since the
hold down time of 30 days (30 days) + the query interval [which is just 1/2
the signature validity period in this example] would have passed).
However, the hold-down timer of our attacked RFC5011 Validator is
only at 25 days; The replay attack at T+5
means its new hold-time timer actually started at T+10, and thus
at this time it's real hold-down timer is at T+35 - T+10 = 25
days, which is less than the RFC5011 required 30 days and (T+35 minus T+10); thus the RFC5011 won't consider
it a valid trust anchor addition yet. yet, as the required 30 days have
not yet elapsed.

T+36 The Zone Signer, believing K_new is safe to use, switches their
active signing KSK to K_new and publishes a new RRSIG, signed with
K_new, and covering the DNSKEY set. Non-attacked RFC5011 validators,
with a hold-down timer of at least 30 days, would have accepted
K_new into their set of trusted keys. But, because our attacked
RFC5011 Validator now has a hold-down timer for K_new at of only 26
days, it will fail failed to accept K_new as a trust anchor. Since K_old is
no longer being used, used to sign the zone's DNSKEYs, all the DNSKEY
records from the zone signed by K_new will be treated as invalid. Subsequently,
all keys in the key set are now unusable, invalidating all of the records in the zone of any type and name. DNS tree below the zone's apex will be
deemed invalid by DNSSEC.

6. Minimum RFC5011 Timing Requirements

6.1. Timing Requirements For Adding a New KSK

Given the attack description in Section 5, the correct minimum length
of time required for the Zone Signer to wait after publishing K_new
but before exclusively using K_new it and newer keys is:

waitTime

addWaitTime = addHoldDownTime
+ (DNSKEY RRSIG Signature Validity) SigExpirationTime
+ MAX(MIN((DNSKEY RRSIG Signature Validity) / 2,
MAX(original TTL of K_old DNSKEY RRSet) / 2,
15 days),
1 hour) activeRefresh
+ activeRefreshOffset
+ 2 * MAX(TTL of all records)

The

Where activeRefresh time is defined by RFC5011 "Active Refresh" requirements state that: by:

A resolver that has been configured for an automatic update
of keys from a particular trust point MUST query that trust
point (e.g., do a lookup for the DNSKEY RRSet and related
RRSIG records) no less often than the lesser of 15 days, half
the original TTL for the DNSKEY RRSet, or half the RRSIG
expiration interval and no more often than once per hour.

This translates to the following equation:

activeRefresh = MAX(1 hour,
MIN(SigExpirationTime / 2,
MAX(TTL of K_old DNSKEY RRSet) / 2,
15 days)
)

The activeRefreshOffset term must be added for situations where the
activeRefresh value is not a factor of "30 days". Specifically,
activeRefreshOffset will be "(30 days) % activeRefresh", where % is
the mathematical mod operator (which calculates the remainder in a
division problem). This will frequently be zero, but could be nearly
as large as activeRefresh itself. For simplicity, setting the
activeRefreshOffset to the activeRefresh value itself is safe.

The full expanded equation, with activeRefreshOffset set to
activeRefresh for simplicity, is:

addWaitTime = addHoldDownTime
+ SigExpirationTime
+ 2 * MAX(1 hour,
MIN(SigExpirationTime / 2,
MAX(TTL of K_old DNSKEY RRSet) / 2,
15 days)
)
+ 2 * MAX(TTL of all records)

The important timing constraint introduced by this memo relates to
the last point at which a validating resolver may have received a
replayed the original DNSKEY set (K_old) without the new key. It's
the set, containing K_old and not K_new. The
next query of the RFC5011 validator that the assured at which K_new will be seen
without a the potential for a replay afterward. attack will occur after the
publication time plus SigExpirationTime. Thus, the latest time that
a RFC5011 validator Validator may begin their hold down timer is an "Active
Refresh" period after the last point that an attacker can replay the
K_old DNSKEY set. The "Active Refresh" interval used by a RFC5011 validator is
determined by the larger of (DNSKEY RRSIG Signature Validity) and
(original TTL for the DNSKEY RRSet). The Following text assumes that
(DNSKEY RRSIG Signature Validity) is larger of the two, which is
operationally more common today.

Thus, the worst case scenario of this attack is when if the
attacker can replay K_old just seconds before the (DNSKEY RRSIG Signature Validity). If a
RFC5011 validator picks up
Validity) field of the last K_old at this this point, it will not have only RRSIG.

RFC5011 also discusses a hold down timer started as retryTime value for failed queries. Our
equation cannot take into account undeterministic failure situations,
so it will have been reset by previous
replays. It's not until the next "Active Refresh" time that they'll
pick up K_new with assurance, and thus start their (final) hold down
timer. Thus, this is not at (DNSKEY RRSIG Signature Validity) time
past publication but may might be significantly longer based on wise to extend the zone's
DNSSEC parameters. addWaitTime by some factor of
retryTime, which is defined in RFC5011 as:

retryTime = MAX (1 hour,
MIN (1 day,
.1 * TTL of K_old DNSKEY RRset,
.1 * SigExpirationTime))

The extra 2 * MAX(TTL of all records) is the standard added safety
margin when dealing with DNSSEC due to caching that can take place.
Because the 5011 steps require direct validation using the signature
validity, the authors aren't yet convinced it is needed in this
particular case, but it is prudent to include it for added assurance.

Note: our notion of addWaitTime is called "Itrp" in Section 3.3.4.1
of [RFC7583]. The equation for Itrp in RFC7583 is insecure as it
does not include the SigExpirationTime listed above. The Itrp
equation in RFC7583 also does not include the 2*TTL safety margin,
though that is an operational consideration and not necessarily as
critical.

6.1.1. Example Results

For the parameters listed in Section 5.1, the activeRefreshOffset is
0, since 30 days is evenly divisible by activeRefresh (1/2 day), and
our example:

waitTime resulting addWaitTime is:

addWaitTime = 30
+ 10
+ 10 1 / 2
+ 2 * (1) (days)

waitTime

addWaitTime = 47 42.5 (days)

This hold-down time addWaitTime of 47 42.5 days is 12 12.5 days longer than just the (frequently
perceived) 35 days in the example at T+35 above. hold
down timer.

6.2. Timing Requirements For Revoking an Old KSK

It is important to note that this value issue affects not just the
publication of new DNSKEYs intended to be used as trust anchors, but
also the length of time required to continuously publish a DNSKEY
with the revoke bit set. Both of these publication timing
requirements are affected by the attacks described in this document. document,
but with revocation the key is revoked immediately and the
addHoldDown timer does not apply. Thus the minimum amount of time
that a Trust Anchor Publisher must wait before removing a revoked key
from publication is:

remWaitTime = SigExpirationTime
+ MAX(1 hour,
MIN((SigExpirationTime) / 2,
MAX(TTL of K_old DNSKEY RRSet) / 2,
15 days),
1 hour)
+ 2 * MAX(TTL of all records)

Note that the activeRefreshOffset time does not apply to this
equation.

Note that our notion of remWaitTime is called "Irev" in
Section 3.3.4.2 of [RFC7583]. The equation for Irev in RFC7583 is
insecure as it does not include the SigExpirationTime listed above.
The Irev equation in RFC7583 also does not include the 2*TTL safety
margin, though that is an operational consideration and not
necessarily as critical.

Note also that adding retryTime intervals to the remWaitTime may be
wise, just as it was for addWaitTime in Section 6.

6.2.1. Example Results

For the parameters listed in Section 5.1, our example:

remwaitTime = 10
+ 1 / 2
+ 2 * (1) (days)

remwaitTime = 12.5 (days)

Note that for the values in this example produce a length shorter
than the recommended 30 days in RFC5011's section 6.6, step 3. Other
values of SigExpirationTime and the original TTL of the K_old DNSKEY
RRSet, however, can produce values longer than 30 days.

Note that because revocation happens immediately, an attacker has a
much harder job tricking a RFC5011 Validator into leaving a trust
anchor in place, as the attacker must successfully replay the old
data for every query a RFC5011 Validator sends, not just one.

7. IANA Considerations

This document contains no IANA considerations.

8. Operational Considerations

A companion document to RFC5011 was expected to be published that
describes the best operational practice considerations from the
perspective of a zone publisher and Trust Anchor Publisher. However,
this companion document has yet to be published. The authors of this
document hope that it will at some point in the future, as RFC5011
timing can be tricky as we have shown shown, and we do not suggest "good
operational practice" that might be associated with a BCP on the
subject. is clearly
warranted. This document is intended only to fill a single
operational void that results which, when left misunderstood, can result in
serious security ramifications (specifically a denial of
service attack against an RFC5011 Validator). ramifications. This document does not attempt to
document any other missing operational guidance for zone publishers.

9. Security Considerations

This document, is solely about the security considerations with
respect to the Trust Anchor Publisher of RFC5011 trust anchors /
keys.
DNSKEYs. Thus the entire document is a discussion of Security
Considerations when rolling adding or removing DNSKEYs from trust anchor
storage using the RFC5011 process.

For simplicity, this document assumes that the Trust Anchor Publisher
will use a consistent RRSIG validity period. Trust Anchor Publishers
that vary the length of RRSIG validity periods will need to adjust
the SigExpirationTime value accordingly so that the equations in
Section 6 and Section 6.2 use a value that coincides with the last
time a replay of older RRSIGs will no longer succeed.

10. Acknowledgements

The authors would like to especially thank to Michael StJohns for his
help and advice and the care and thought he put into RFC5011 itself.
We would also like to thank Bob Harold, Shane Kerr, Matthijs Mekking,
Duane Wessels, Petr Petr Spacek, and the dnsop working group who have
assisted with this document.

11. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997. 1997, <https://www.rfc-
editor.org/info/rfc2119>.

[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, DOI 10.17487/RFC4033, March 2005,
<http://www.rfc-editor.org/info/rfc4033>.
<https://www.rfc-editor.org/info/rfc4033>.

[RFC5011] StJohns, M., "Automated Updates of DNS Security (DNSSEC)
Trust Anchors", STD 74, RFC 5011, DOI 10.17487/RFC5011,
September 2007, <http://www.rfc-editor.org/info/rfc5011>. <https://www.rfc-editor.org/info/rfc5011>.

[RFC7583] Morris, S., Ihren, J., Dickinson, J., and W. Mekking,
"DNSSEC Key Rollover Timing Considerations", RFC 7583,
DOI 10.17487/RFC7583, October 2015, <https://www.rfc-
editor.org/info/rfc7583>.

[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", RFC 7719, DOI 10.17487/RFC7719, December
2015, <http://www.rfc-editor.org/info/rfc7719>. <https://www.rfc-editor.org/info/rfc7719>.

Appendix A. Real World Example: The 2017 Root KSK Key Roll

In 2017, ICANN expects to (or has, depending on when you're reading
this) roll the key signing key (KSK) for the root zone. The relevant
parameters associated with the root zone at the time of this writing
is as follows:

addHoldDownTime: 30 days
Old DNSKEY RRSIG Signature Validity: SigExpirationTime: 21 days
Old DNSKEY TTL: 2 days

Thus, sticking this information into the equation in
Section Section 6 yields (in days):

waitTime = addHoldDownTime
+ (DNSKEY RRSIG Signature Validity)
+ MAX(MIN((DNSKEY RRSIG Signature Validity) / 2,
MAX(original TTL of K_old DNSKEY RRSet) / 2,
15 days),
1 hour)
+ 2 * MAX(TTL of all records)

waitTime

addWaitTime = 30
+ (21)
+ MAX(MIN((21) / 2,
MAX(2 / 2,
15 days)),
1 hour)
+ 2 * MAX(2)

waitTime

addWaitTime = 30 + 21 + MAX(MIN(11.5, MAX( 1, 15)), 1 hour) + 4

waitTime

addWaitTime = 30 + 21 + 11.5 1 + 4

waitTime

addWaitTime = 66.5 56 days

Note that we use a activeRefreshOffset of 0, since 30 days is evenly
divisible by activeRefresh (1 day).

Thus, ICANN should wait 66.5 a minimum of 56 days before switching to the
newly published KSK and (and 26 days before removing the old revoked key
once it is published as revoked. revoked). ICANN's current plans are to wait
70 days before using the new KEY and 69 days before removing the old,
revoked key. Thus, their current rollover plans are sufficiently
secure from the attack discussed in this memo.

Appendix B. Changes / Author Notes.

From Individual-00 to DNSOP-00:

o Filename change.

From -00 to -01:

o Added Revocation processing (including "Timing Associated with
Revocation")

o Added real world example.

o Fixed some typoes and missing references.

From Ind-00 to -02:

Additional background and clarifications in abstract.

Better separation in attack description between attacked and non-
attacked resolvers.

Some language cleanup.

Clarified that this is maths ( and math is hard, let's go
shopping!)

Changed to " <?rfc include='reference....'?> " style references.

From -02 to -03:

Minor changes from Bob Harold

Clarified why 3/2 signature validity is needed

Changed min wait time math to include TTL value as well

From -03 to -04:

Fixed the waitTime equation to handle the difference between the
usage of the expiration time and the Active Refresh time.

More clarification text and text changes proposed by Petr Spacek

From -04 to -05:

Clarifications about signing using only new keys, vs old ones too

Pre-DNSOP document: From hardaker-04 to ietf-00:

Just rebranding.

From ietf-00 to ietf-01:

Added discussion surrounding revocation everywhere

Fixed the text about the formula

Another complete re-read for word-smithing

Authors' Addresses

Wes Hardaker
USC/ISI
P.O. Box 382
Davis, CA 95617
US

Email: ietf@hardakers.net

Warren Kumari
Google
1600 Amphitheatre Parkway
Mountain View, CA 94043
US

Email: warren@kumari.net