draft-ietf-dprive-padding-policy-04.txt   draft-ietf-dprive-padding-policy-05.txt 
Network Working Group A. Mayrhofer Network Working Group A. Mayrhofer
Internet-Draft nic.at GmbH Internet-Draft nic.at GmbH
Intended status: Experimental February 6, 2018 Intended status: Experimental April 12, 2018
Expires: August 10, 2018 Expires: October 14, 2018
Padding Policy for EDNS(0) Padding Policy for EDNS(0)
draft-ietf-dprive-padding-policy-04 draft-ietf-dprive-padding-policy-05
Abstract Abstract
RFC 7830 specifies the EDNS(0) 'Padding' option, but does not specify RFC 7830 specifies the EDNS(0) 'Padding' option, but does not specify
the actual padding length for specific applications. This memo lists the actual padding length for specific applications. This memo lists
the possible options ("Padding Policies"), discusses implications of the possible options ("Padding Policies"), discusses implications of
each of these options, and provides a recommended (experimental) each of these options, and provides a recommended (experimental)
option. option.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 10, 2018. This Internet-Draft will expire on October 14, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. General Guidance . . . . . . . . . . . . . . . . . . . . . . 3 3. General Guidance . . . . . . . . . . . . . . . . . . . . . . 3
4. Padding Strategies . . . . . . . . . . . . . . . . . . . . . 3 4. Padding Strategies . . . . . . . . . . . . . . . . . . . . . 3
4.1. Block Length Padding . . . . . . . . . . . . . . . . . . 3 4.1. Block Length Padding - Recommended Strategy . . . . . . . 3
4.2. Maximal Length Padding ('The Full Monty') . . . . . . . . 4 4.2. Other Sensible Strategies . . . . . . . . . . . . . . . . 5
4.3. Random Length Padding . . . . . . . . . . . . . . . . . . 4 4.2.1. Maximal Length Padding . . . . . . . . . . . . . . . 5
4.4. Random Block Length Padding . . . . . . . . . . . . . . . 5 4.2.2. Random Length Padding . . . . . . . . . . . . . . . . 5
5. Recommended Strategy . . . . . . . . . . . . . . . . . . . . 5 4.2.3. Random Block Length Padding . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. draft-ietf-dprive-padding-policy-04 . . . . . . . . . . . 7 8.1. draft-ietf-dprive-padding-policy-05 . . . . . . . . . . . 7
9.2. draft-ietf-dprive-padding-policy-03 . . . . . . . . . . . 7 8.2. draft-ietf-dprive-padding-policy-04 . . . . . . . . . . . 7
9.3. draft-ietf-dprive-padding-policy-02 . . . . . . . . . . . 7 8.3. draft-ietf-dprive-padding-policy-03 . . . . . . . . . . . 8
9.4. draft-ietf-dprive-padding-policy-01 . . . . . . . . . . . 7 8.4. draft-ietf-dprive-padding-policy-02 . . . . . . . . . . . 8
9.5. draft-ietf-dprive-padding-policy-00 . . . . . . . . . . . 7 8.5. draft-ietf-dprive-padding-policy-01 . . . . . . . . . . . 8
9.6. draft-mayrhofer-dprive-padding-profiles-00 . . . . . . . 8 8.6. draft-ietf-dprive-padding-policy-00 . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 8.7. draft-mayrhofer-dprive-padding-profiles-00 . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . 8 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . 8 9.1. Normative References . . . . . . . . . . . . . . . . . . 8
Appendix A. Non-sensible Padding Policies . . . . . . . . . . . 8 9.2. Informative References . . . . . . . . . . . . . . . . . 9
A.1. No Padding . . . . . . . . . . . . . . . . . . . . . . . 8 Appendix A. Non-sensible Padding Policies . . . . . . . . . . . 9
A.1. No Padding . . . . . . . . . . . . . . . . . . . . . . . 9
A.2. Fixed Length Padding . . . . . . . . . . . . . . . . . . 9 A.2. Fixed Length Padding . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
[RFC7830] specifies the Extensions Mechanisms for DNS (EDNS(0)) [RFC7830] specifies the Extensions Mechanisms for DNS (EDNS(0))
"Padding" option, which allows DNS clients and servers to "Padding" option, which allows DNS clients and servers to
artificially increase the size of a DNS message by a variable number artificially increase the size of a DNS message by a variable number
of bytes, hampering size-based correlation of encrypted DNS messages. of bytes, hampering size-based correlation of encrypted DNS messages.
However, RFC 7830 deliberately does not specify the actual length of However, RFC 7830 deliberately does not specify the actual length of
padding to be used. This memo discusses options regarding the actual padding to be used. This memo discusses options regarding the actual
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3. General Guidance 3. General Guidance
EDNS(0) options space: The maximum message length as dictated by EDNS(0) options space: The maximum message length as dictated by
protocol limitation limits the space for EDNS(0) options. Since protocol limitation limits the space for EDNS(0) options. Since
padding will reduce the message space available to other EDNS(0) padding will reduce the message space available to other EDNS(0)
options, "Padding" MUST be the last EDNS(0) option applied before a options, "Padding" MUST be the last EDNS(0) option applied before a
DNS message is sent. DNS message is sent.
Resource Conservation: Especially in situations where networking and Resource Conservation: Especially in situations where networking and
processing resources are scarce (eg. battery powered long-life processing resources are scarce (e.g. battery powered long-life
devices, low bandwidth or high cost links), the tradeoff between devices, low bandwidth or high cost links), the tradeoff between
increased size of padded DNS messages and the corresponding gain in increased size of padded DNS messages and the corresponding gain in
confidentiality must be carefully considered. confidentiality must be carefully considered.
Transport Protocol Independence: The message size used as input to Transport Protocol Independence: The message size used as input to
the various padding strategies MUST be calculated excluding the the various padding strategies MUST be calculated excluding the
potential extra 2-octet length field used in TCP transport. potential extra 2-octet length field used in TCP transport.
Otherwise, the padded (observable) size of the DNS packets could Otherwise, the padded (observable) size of the DNS packets could
signifcantly change between different transport protocols, and reveal significantly change between different transport protocols, and
an indication of the original (unpadded) length. For example, given reveal an indication of the original (unpadded) length. For example,
a "Block Length" padding strategy with a block length of 32 octets, given a "Block Length" padding strategy with a block length of 32
and a DNS message with a size of 59 octets, the message would be octets, and a DNS message with a size of 59 octets, the message would
padded to 64 octets when transported over UDP. If that same message be padded to 64 octets when transported over UDP. If that same
was transported over TCP, and the padding strategy would consider the message was transported over TCP, and the padding strategy would
extra 2 octects of the length field (61 octets in total), the padded consider the extra 2 octets of the length field (61 octets in total),
message would be 96 octets long (as the minimum length of the Padding the padded message would be 96 octets long (as the minimum length of
option is 4 octets). the Padding option is 4 octets).
4. Padding Strategies 4. Padding Strategies
This section is a non-exhaustive list of sensible strategies in This section contains a recommended strategy, as well as a non-
choosing padding length. Note that, for completeness, Appendix A exhaustive list of other sensible strategies in choosing padding
contains two more (non-sensible) strategies. length. Note that, for completeness, Appendix A contains two more
(non-sensible) strategies.
4.1. Block Length Padding 4.1. Block Length Padding - Recommended Strategy
Based on empirical research performed by Daniel K. Gillmor
[dkg-padding-ndss], EDNS Padding SHOULD be performed following the
"Block Length Padding" strategy as follows:
(1) Clients SHOULD pad queries to the closest multiple of 128
octets.
(2) If a Server receives a query that includes the EDNS(0) Padding
Option, it MUST pad the corresponding response (See Section 4 of
RFC7830) and SHOULD pad the corresponding response to a multiple
of 468 octets (see below).
Note that the recommendation above applies only if DNS transport is
encrypted (See Section 6 of RFC 7830).
In Block Length Padding, a sender pads each message so that its In Block Length Padding, a sender pads each message so that its
padded length is a multiple of a chosen block length. This creates a padded length is a multiple of a chosen block length. This creates a
greatly reduced variety of message lengths. An implementor needs to greatly reduced variety of message lengths. An implementor needs to
consider that even the zero-length EDNS(0) Padding Option increases consider that even the zero-length EDNS(0) Padding Option increases
the length of the packet by 4 octets. the length of the packet by 4 octets.
Options: Block Length - values between 16 and 128 octets for the Options: Block Length - values between 16 and 128 octets for the
queries seem reasonable, responses will require larger block sizes queries seem reasonable, responses will require larger block sizes
(see [dkg-padding-ndss] and Section 5 for a discussion). (see [dkg-padding-ndss] and above for a discussion).
Very large block lengths will have confidentiality properties similar Very large block lengths will have confidentiality properties similar
to the "Maximum Length Padding" strategy (Section 4.2), since almost to the "Maximal Length Padding" strategy (Section 4.2.1), since
all messages will fit into a single block. In that case, reasonable almost all messages will fit into a single block. In that case,
values may be 288 bytes for the query (the maximum size of a one- reasonable values may be 288 bytes for the query (the maximum size of
question query over TCP, without any EDNS(0) options), and the a one-question query over TCP, without any EDNS(0) options), and the
EDNS(0) buffer size of the server for the responses. EDNS(0) buffer size of the server for the responses.
Advantages: This policy is reasonably easy to implement, reduces the Advantages: This policy is reasonably easy to implement, reduces the
variety of message ("fingerprint") sizes significantly, and does not variety of message ("fingerprint") sizes significantly, and does not
require a source of (pseudo) random numbers, since the padding length require a source of (pseudo) random numbers, since the padding length
required can be derived from the actual (unpadded) message. required can be derived from the actual (unpadded) message.
Disadvantage: Given an unpadded message and the block size of the Disadvantage: Given an unpadded message and the block size of the
padding (which is assumed to be public knowledge once a server is padding (which is assumed to be public knowledge once a server is
reachable), the size of a padded message can be predicted. reachable), the size of a padded message can be predicted.
Therefore, minimum and maximum length of the unpadded message are Therefore, minimum and maximum length of the unpadded message are
known. known.
Block Length Padding is the currently RECOMMENDED strategy (see The Block Size will interact with the MTU size. Especially for
Section 5). length values that are a large fraction of the MTU, unless the block
length is chosen so that a multiple just fits into the MTU, Block
Length Padding may cause unneccessary fragmentation for UDP based
delivery. Also, chosing a block length larger than the MTU of course
forces to always fragment.
4.2. Maximal Length Padding ('The Full Monty') The empirical research cited above performed a simulation of padding,
based on real-world DNS traffic captured on busy recursive resolvers
of a research network. The evaluation of the performance of
individual padding policies was based on a "cost to attacker" and
"cost to defender" function, where the "cost to attacker" was defined
as the percentage of query/response pairs falling into the same size
bucket, and "cost to defender" as the size factor between padded and
unpadded messages. Padding with a block size of 128 bytes on the
query side, and 468 bytes on the response side was considered the
optimum trade-off between defender and attacker cost. The response
block size of 468 was chosen so that 3 blocks of 468 octets would
still comfortably fit into typical Maximum Transmission Unit (MTU)
size values.
The Block Size will interact with the MTU size. Especially for
length values that are a large fraction of the MTU, unless the block
length is chosen so that a multiple just fits into the MTU, Block
Padding may cause unneccessary fragmentation for UDP based delivery.
Also, chosing a block length larger than the MTU of course always
forces to always fragment.
Note: Once DNSSEC validating clients become more prevalent, observed
size patterns are expected to change significantly. In such case,
the recommended strategy might need to be revisited.
4.2. Other Sensible Strategies
4.2.1. Maximal Length Padding
In Maximal Length Padding the sender pads every message to the In Maximal Length Padding the sender pads every message to the
maximum size as allowed by protocol negotiations. maximum size as allowed by protocol negotiations.
Advantages: Maximal Length Padding, when combined with encrypted Advantages: Maximal Length Padding, when combined with encrypted
transport, provides the highest possible level of message size transport, provides the highest possible level of message size
confidentiality. confidentiality.
Disadvantages: Maximal Length Padding is wasteful, and requires Disadvantages: Maximal Length Padding is wasteful, and requires
resources on the client, all intervening network and equipment, and resources on the client, all intervening network and equipment, and
the server. the server. Depending on the negotiated size, this strategy will
commonly exceed the MTU, and then result in a consistent number of
fragments reducing delivery probability when datagram based transport
(such as UDP) is used.
Maximal Length Padding is NOT RECOMMENDED. Maximal Length Padding is NOT RECOMMENDED.
4.3. Random Length Padding 4.2.2. Random Length Padding
When using Random Length Padding, a sender pads each message with a When using Random Length Padding, a sender pads each message with a
random amount of padding. Due to the size of the EDNS(0) Padding random amount of padding. Due to the size of the EDNS(0) Padding
Option itself, each message size is hence increased by at least 4 Option itself, each message size is hence increased by at least 4
octets. The upper limit for pading is the maximum message size. octets. The upper limit for padding is the maximum message size.
However, a client or server may choose to impose a lower maximum However, a client or server may choose to impose a lower maximum
padding length. padding length.
Options: Maximum and minimum padding length. Options: Maximum and minimum padding length.
Advantages: Theoretically, this policy should create a natural Advantages: Theoretically, this policy should create a natural
"distribution" of message sizes. "distribution" of message sizes.
Disadvantage: This policy requires a good source of (pseudo) which Disadvantage: This policy requires a good source of (pseudo) random
can keep up with the required message rates. Especially on busy numbers which can keep up with the required message rates.
servers, this may be a hindrance. Especially on busy servers, this may be a hindrance.
According to the limited empirical data available, Random Length According to the limited empirical data available, Random Length
Padding performs slightly worse than Block Length Padding. Padding performs slightly worse than Block Length Padding.
4.4. Random Block Length Padding 4.2.3. Random Block Length Padding
This policy combines Block Length Padding with a random component. This policy combines Block Length Padding with a random component.
Specifically, a sender randomly chooses between a few block length Specifically, a sender randomly chooses between a few block length
values and then applies Block Length Padding based on the chosen values and then applies Block Length Padding based on the chosen
block length. The random selection of block length might even be block length. The random selection of block length might even be
reasonably based on a "weak" source of randomness, such as the reasonably based on a "weak" source of randomness, such as the
transction ID of the message. transaction ID of the message.
Options: Number of and the values for the set of Block Lengths, Options: Number of and the values for the set of Block Lengths,
source of "randomness" source of "randomness"
Advantages: Compared to Block Length Padding, this creates more Advantages: Compared to Block Length Padding, this creates more
variety in the resulting message sizes for a certain individual variety in the resulting message sizes for a certain individual
original message length. Also, compared to "Random Length Padding", original message length. Also, compared to "Random Length Padding",
it might not require a "full blown" random number source. it might not require a "full blown" random number source.
Disadvantage: Requires more implementation effort compared to simple Disadvantage: Requires more implementation effort compared to simple
Block Length Padding Block Length Padding
Random Block Length Padding (as other combinations of padding Random Block Length Padding (as other combinations of padding
strategies) requires further empirical study. strategies) requires further empirical study.
5. Recommended Strategy 5. Acknowledgements
Based on empirical research performed by Daniel K. Gillmor
[dkg-padding-ndss], EDNS Padding SHOULD be performed as follows:
(1) Clients SHOULD pad queries to the closest multiple of 128
octets.
(2) If a Server receives a query that includes the EDNS(0) Padding
Option, it MUST pad the corresponding response (See Section 4 of
RFC7830) and SHOULD pad the corresponding response to a multiple
of 468 octects.
Note that the recommendation above does apply only if DNS transport
is encrypted (See Section 6 of RFC 7830).
The empirical research cited above performed a simulation of padding,
based on real-world DNS traffic captured on busy recursive resolvers
of a research network. The evaluation of the performance of
individual padding policies was based on a "cost to attacker" and
"cost to defender" function, where the "cost to attacker" was defined
as the percentage of query/response pairs falling into the same size
bucket, and "cost to defender" as the size factor between padded and
unpadded messages. Padding with a block size of 128 bytes on the
query side, and 468 bytes on the response side was considered the
optimum trade-off between defender and attacker cost. The response
block size of 468 was chosen so that 3 blocks of 468 octets would
still comfortably fit into typical MTU values.
Note: Once DNSSEC validating clients become more prevalent, observed
size patterns are expected to change significantly. In such case,
the recommended strategy might need to be revisited.
6. Acknowledgements
Daniel K. Gillmor performed empirical research out of which the Daniel K. Gillmor performed empirical research out of which the
"Recommended Strategy" was copied. Stephane Bortzmeyer and Hugo "Recommended Strategy" was copied. Stephane Bortzmeyer and Hugo
Connery provided text. Shane Kerr, Sara Dickinson, Paul Hoffman Connery provided text. Shane Kerr, Sara Dickinson, Paul Hoffman,
performed reviews and provided substantial comments. Magnus Westerlund, Charlie Kaufman, Joe Clarke and Meral Shirazipour
performed reviews or provided substantial comments.
7. IANA Considerations 6. IANA Considerations
This document has no considerations for IANA. This document has no considerations for IANA.
8. Security Considerations 7. Security Considerations
The choice of the right padding policy (and the right parameters for The choice of the right padding policy (and the right parameters for
the chosen policy) has a significant impact on the resilience of the chosen policy) has a significant impact on the resilience of
encrypted DNS against size-based correlation attacks. Therefore, any encrypted DNS against size-based correlation attacks. Therefore, any
implementor of EDNS(0) Padding must carefully consider which policies implementor of EDNS(0) Padding must carefully consider which policies
to implement, the default policy chosen, which parameters to make to implement, the default policy chosen, which parameters to make
configurable, and the default parameter values. configurable, and the default parameter values.
No matter how carefully a client selects their Padding policy, this No matter how carefully a client selects their Padding policy, this
effort can be jeopardized if the server chooses to apply an effort can be jeopardized if the server chooses to apply an
inffective Padding policy to the corresponding response packets. ineffective Padding policy to the corresponding response packets.
Therefore, a client applying Padding may want to choose a DNS server Therefore, a client applying Padding may want to choose a DNS server
which does apply at least an equally effective Padding policy on which does apply at least an equally effective Padding policy on
responses. responses.
Note that even with encryption and padding, it might be trivial to Note that even with encryption and padding, it might be trivial to
identify that the observed traffic is DNS. Also, padding does not identify that the observed traffic is DNS. Also, padding does not
prevent information leak via other side channels (particularly timing prevent information leak via other side channels (particularly timing
information and number of query/response pairs). Counter-measures information and number of query/response pairs). Counter-measures
against such other side channels could include injecting artificial against such other side channels could include injecting artificial
"cover traffic" into the stream of DNS messages, or delaying DNS "cover traffic" into the stream of DNS messages, or delaying DNS
responses by a certain amount of jitter. Such strategies are out of responses by a certain amount of jitter. Such strategies are out of
scope of this document. Additionally, there is neither enough scope of this document. Additionally, there is neither enough
theoretic analysis nor experimental data available to recommend any theoretic analysis nor experimental data available to recommend any
such countermeasures. such countermeasures.
9. Changes 8. Changes
[Note to RFC Editors: This whole section is to be removed before [Note to RFC Editors: This whole section is to be removed before
publication] publication]
9.1. draft-ietf-dprive-padding-policy-04 8.1. draft-ietf-dprive-padding-policy-05
Changes based on outcomes of IETF-wide LC + various reviews: Meral
Shirazipour (Gen-ART), Charlie Kaufmann (SECDIR), Joe Clarke (OPSDIR
- changed document flow based on comments),
8.2. draft-ietf-dprive-padding-policy-04
Changes based on WGLC: Changed implementor consideration text in Changes based on WGLC: Changed implementor consideration text in
Security Con section (Sara), moved "No Padding" and "Fixed Length Security Con section (Sara), moved "No Padding" and "Fixed Length
Padding" to appendix (Stephane, Paul), Changed TODO in Random Padding Padding" to appendix (Stephane, Paul), Changed TODO in Random Padding
to info from empirical study (Stephen), Added note to pad only if to info from empirical study (Stephen), Added note to pad only if
transport encrypted (Stephen), added intro text referencing to transport encrypted (Stephen), added intro text referencing to
DNSoTLS and DNSoDTLS (Stephane), added text about timing/jitter to DNSoTLS and DNSoDTLS (Stephane), added text about timing/jitter to
security considerations. security considerations.
9.2. draft-ietf-dprive-padding-policy-03 8.3. draft-ietf-dprive-padding-policy-03
Editorial changes in various spots. Added text about excluding TCP Editorial changes in various spots. Added text about excluding TCP
length field, more security considerations, addressing Sara's other length field, more security considerations, addressing Sara's other
feedback to -02. feedback to -02.
9.3. draft-ietf-dprive-padding-policy-02 8.4. draft-ietf-dprive-padding-policy-02
Changed Document Status to Experimental, added "maximum length" Changed Document Status to Experimental, added "maximum length"
padding policy, reworded "block length" policy, some editorial padding policy, reworded "block length" policy, some editorial
changes. changes.
9.4. draft-ietf-dprive-padding-policy-01 8.5. draft-ietf-dprive-padding-policy-01
Some (mostly editorial) changes to text. Added "Recommendation" Some (mostly editorial) changes to text. Added "Recommendation"
section based on dkg's research. section based on dkg's research.
9.5. draft-ietf-dprive-padding-policy-00 8.6. draft-ietf-dprive-padding-policy-00
Initial (mostly unmodified) WG version. Changed "Profile" to Initial (mostly unmodified) WG version. Changed "Profile" to
"Policy" to avoid confusion with the (D)TLS profiles document. "Policy" to avoid confusion with the (D)TLS profiles document.
9.6. draft-mayrhofer-dprive-padding-profiles-00 8.7. draft-mayrhofer-dprive-padding-profiles-00
Initial version Initial version
10. References 9. References
10.1. Normative References 9.1. Normative References
[dkg-padding-ndss] [dkg-padding-ndss]
Gillmor, D., "Empirical DNS Padding Policy", March 2017, Gillmor, D., "Empirical DNS Padding Policy", March 2017,
<https://dns.cmrg.net/ <https://dns.cmrg.net/
ndss2017-dprive-empirical-DNS-traffic-size.pdf>. ndss2017-dprive-empirical-DNS-traffic-size.pdf>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC7830] Mayrhofer, A., "The EDNS(0) Padding Option", RFC 7830, [RFC7830] Mayrhofer, A., "The EDNS(0) Padding Option", RFC 7830,
DOI 10.17487/RFC7830, May 2016, DOI 10.17487/RFC7830, May 2016,
<https://www.rfc-editor.org/info/rfc7830>. <https://www.rfc-editor.org/info/rfc7830>.
10.2. Informative References 9.2. Informative References
[RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D., [RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
and P. Hoffman, "Specification for DNS over Transport and P. Hoffman, "Specification for DNS over Transport
Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
2016, <https://www.rfc-editor.org/info/rfc7858>. 2016, <https://www.rfc-editor.org/info/rfc7858>.
[RFC8094] Reddy, T., Wing, D., and P. Patil, "DNS over Datagram [RFC8094] Reddy, T., Wing, D., and P. Patil, "DNS over Datagram
Transport Layer Security (DTLS)", RFC 8094, Transport Layer Security (DTLS)", RFC 8094,
DOI 10.17487/RFC8094, February 2017, DOI 10.17487/RFC8094, February 2017,
<https://www.rfc-editor.org/info/rfc8094>. <https://www.rfc-editor.org/info/rfc8094>.
 End of changes. 34 change blocks. 
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