Light-Weight Implementation Guidance (lwig) D. Migault
Internet-Draft Ericsson
Intended status: Informational T. Guggemos
Expires: October 15, 2021 LMU Munich
April 13, 2021
Minimal ESP
draft-ietf-lwig-minimal-esp-05
Abstract
This document describes a minimal implementation of the IP
Encapsulation Security Payload (ESP) defined in RFC 4303. Its
purpose is to enable implementation of ESP with a minimal set of
options to remain compatible with ESP as described in RFC 4303. A
minimal version of ESP is not intended to become a replacement of the
RFC 4303 ESP. Instead, a minimal implementation is expected to be
optimized for constrained environment while remaining interoperable
with implementations of RFC 4303 ESP. Some constrains include
limiting the number of flash writes, handling frequent wakeup / sleep
states, limiting wakeup time, or reducing the use of random
generation.
This document does not update or modify RFC 4303, but provides a
compact description of how to implement the minimal version of the
protocol. RFC 4303 remains the authoritative description.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 15, 2021.
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Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Requirements Notation . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Security Parameter Index (SPI) (32 bit) . . . . . . . . . . . 4
3.1. Considerations over SPI generation . . . . . . . . . . . 5
4. Sequence Number(SN) (32 bit) . . . . . . . . . . . . . . . . 6
5. Padding . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Next Header (8 bit) . . . . . . . . . . . . . . . . . . . . . 9
7. ICV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8. Cryptographic Suites . . . . . . . . . . . . . . . . . . . . 10
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
10. Security Considerations . . . . . . . . . . . . . . . . . . . 12
11. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 12
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
12.1. Normative References . . . . . . . . . . . . . . . . . . 13
12.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Introduction
ESP [RFC4303] is part of the IPsec protocol suite [RFC4301]. IPsec
is used to provide confidentiality, data origin authentication,
connectionless integrity, an anti-replay service (a form of partial
sequence integrity) and limited traffic flow confidentiality.
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Figure 1 describes an ESP Packet. Currently ESP is implemented in
the kernel of major multipurpose Operating Systems (OS). The ESP and
IPsec suite is usually implemented in a complete way to fit multiple
purpose usage of these OS. However, completeness of the IPsec suite
as well as multipurpose scope of these OS is often performed at the
expense of resources, or performance. As a result, constrained
devices are likely to have their own implementation of ESP optimized
and adapted to their specificities such as limiting the number of
flash writes (for each packet or across wake time), handling frequent
wakeup and sleep state, limiting wakeup time, or reducing the use of
random generation. With the adoption of IPsec by IoT devices with
minimal IKEv2 [RFC7815] and ESP Header Compression (EHC) with
[I-D.mglt-ipsecme-diet-esp] or
[I-D.mglt-ipsecme-ikev2-diet-esp-extension], it becomes crucial that
ESP implementation designed for constrained devices remains inter-
operable with the standard ESP implementation to avoid a fragmented
usage of ESP. This document describes the minimal properties an ESP
implementation needs to meet to remain interoperable with [RFC4303]
ESP. In addition, this document also provides a set of options to
implement these properties under certain constrained environments.
This document does not update or modify RFC 4303, but provides a
compact description of how to implement the minimal version of the
protocol. RFC 4303 remains the authoritative description.
For each field of the ESP packet represented in Figure 1 this
document provides recommendations and guidance for minimal
implementations. The primary purpose of Minimal ESP is to remain
interoperable with other nodes implementing RFC 4303 ESP, while
limiting the standard complexity of the implementation.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----
| Security Parameters Index (SPI) | ^Int.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Cov-
| Sequence Number | |ered
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ----
| Payload Data* (variable) | | ^
~ ~ | |
| | |Conf.
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Cov-
| | Padding (0-255 bytes) | |ered*
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| | Pad Length | Next Header | v v
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ------
| Integrity Check Value-ICV (variable) |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: ESP Packet Description
3. Security Parameter Index (SPI) (32 bit)
According to the [RFC4303], the SPI is a mandatory 32 bits field and
is not allowed to be removed.
The SPI has a local significance to index the Security Association
(SA). From [RFC4301] section 4.1, nodes supporting only unicast
communications can index their SA only using the SPI. On the other
hand, nodes supporting multicast communications must also use the IP
addresses and thus SA lookup needs to be performed using the longest
match.
For nodes supporting only unicast communications, it is RECOMMENDED
to index SA with the SPI only. The index MAY be based on the full 32
bits of SPI or a subset of these bits. Some other local constraints
on the node may require a combination of the SPI as well as other
parameters to index the SA.
Values 0-255 MUST NOT be used. As per section 2.1 of [RFC4303],
values 1-255 are reserved and 0 is only allowed to be used internal
and it MUST NOT be sent on the wire.
[RFC4303] does not require the SPI to be randomly generated over 32
bits. However, this is the RECOMMENDED way to generate SPIs as it
provides some privacy benefits and avoids, for example, correlation
between ESP communications. To randomly generate a 32 bit SPI, the
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node generates a random 32 bit value, checks does not fall in the
0-255 range. If the SPI has an acceptable value, it is used to index
the inbound session, otherwise the SPI is re-generated until an
acceptable value is found.
However, some constrained nodes may be less concerned by the privacy
properties associated to SPIs randomly generated. Examples of such
nodes might include sensors looking to reduce their code complexity,
in which case the use of a predictive function to generate the SPI
might be preferred over the generation and handling of random values.
An example of such predictable function may consider the combination
of a fixed value and the memory address of the SAD structure. For
every incoming packet, the node will be able to point the SAD
structure directly from the SPI value. This avoids having a separate
and additional binding between SPI and SAD entries that is involved
for every incoming packet.
3.1. Considerations over SPI generation
SPI that are not randomly generated over 32 bits MAY lead to privacy
and security concerns. As a result, the use of alternative designs
requires careful security and privacy reviews. This section provides
some considerations upon the adoption of alternative designs.
Note that SPI value is used only for inbound traffic, as such the SPI
negotiated with IKEv2 [RFC7296] or [RFC7815] by a peer, is the value
used by the remote peer when it sends traffic. As SPI is only used
for inbound traffic by the peer, this allows each peer to manage the
set of SPIs used for its inbound traffic. Similarly, the privacy
concerns associated with the generation of nonrandom SPI is also
limited to the incoming traffic.
When alternate designs are considered, it is likely that the number
of possible SPIs will be limited. This limit should both consider
the number of inbound SAs - possibly per IP addresses - as well as
the ability for the node to rekey. SPI can typically be used to
proceed to clean key update and the SPI value may be used to indicate
which key is being used. This can typically be implemented by a SPI
being encoded with the Security Association Database (SAD) entry on a
subset of bytes (for example 3 bytes), while the remaining byte is
left to indicate the rekey index.
The use of a smaller number of SPIs across communications comes with
privacy and security concerns. Typically some specific values or
subset of SPI values may reveal the models or manufacturer of the
node implementing ESP. This may raise some privacy issues as an
observer is likely to be able to determine the constrained devices of
the network. In some cases, these nodes may host a very limited
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number of applications - typically a single application - in which
case the SPI would provide some information related to the
application of the user. In addition, the device or application may
be associated with some vulnerabilities, in which case specific SPI
values may be used by an attacker to discover vulnerabilities.
While the use of randomly generated SPI may reduce the leakage or
privacy or security related information by ESP itself, these
information may also be leaked otherwise and a privacy analysis
should consider at least the type of information as well the traffic
pattern. Typically, temperature sensors, wind sensors, used outdoors
do not leak privacy sensitive information and mosty of its traffic is
expected to be outbound traffic. When used indoors, a sensor that
reports every minute an encrypted status of the door (closed or
opened) leaks truly little privacy sensitive information outside the
local network.
4. Sequence Number(SN) (32 bit)
According to [RFC4303], the Sequence Number (SN) is a mandatory 32
bits field in the packet.
The SN is set by the sender so the receiver can implement anti-replay
protection. The SN is derived from any strictly increasing function
that guarantees: if packet B is sent after packet A, then SN of
packet B is strictly greater than the SN of packet A.
Some constrained devices may establish communication with specific
devices, like a specific gateway, or nodes similar to them. As a
result, the sender may know whereas the receiver implements anti-
replay protection or not. Even though the sender may know the
receiver does not implement anti-replay protection, the sender MUST
implement an always increasing function to generate the SN.
Usually, SN is generated by incrementing a counter for each packet
sent. A constrained device may avoid maintaining this context and
use another source that is known to always increase. Typically,
constrained nodes using 802.15.4 Time Slotted Channel Hopping (TSCH),
whose communication is heavily dependent on time, can take advantage
of their clock to generate the SN. A lot of IoT devices are in a
sleep state most of the time wake up and are only awake to perform a
specific operation before going back to sleep. They do have separate
hardware that allows them to wake up after a certain timeout, and
most likely also timers that start running when the device was booted
up, so they might have a concept of time with certain granularity.
This requires to store any information in a stable storage - such as
flash memory - that can be restored across sleeps. Storing
information associated with the SA such as SN requires some read and
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writing operation on a stable storage after each packet is sent as
opposed to SPI or keys that are only written at the creation of the
SA. Such operations are likely to wear out the flash, and slow down
the system greatly, as writing to flash is not as fast as reading.
Their internal clocks/timers might not be very accurate, but they
should be enough to know that each time they wake up their time is
greater than what it was last time they woke up. Using time for SN
would guarantee a strictly increasing function and avoid storing any
additional values or context related to the SN. When the use of a
clock is considered, one should take care that packets associated
with a given SA are not sent with the same time value. Note however
that standard receivers are generally configured with incrementing
counters and, if not appropriately configured, the use of a
significantly larger SN may result in the packet out of the
receiver's windows and that packet being discarded.
For inbound traffic, it is RECOMMENDED that any receiver provides
anti-replay protection, and the size of the window depends on the
ability of the network to deliver packets out of order. As a result,
in an environment where out of order packets is not possible the
window size can be set to one. However, while RECOMMENDED, there are
no requirements to implement an anti-replay protection mechanism
implemented by IPsec. Similarly to the SN the implementation of anti
replay protection may require the device to write the received SN for
every packet, which may in some cases come with the same drawbacks as
those exposed for SN. As a result, some implementations MAY drop an
non required anti replay protection especially when the necessary
resource involved overcomes the benefit of the mechanism. A typical
example might consider an IoT device such as a temperature sensor
that is sending a temperature every 60 seconds, and that receives an
acknowledgment from the receiver. In such cases, the ability to
spoof and replay an acknowledgement is of limited interest and may
not justify the implementation of an anti replay mechanism.
Receiving peers may also implement their own anti-replay mechanism.
Typically, when the sending peer is using SN based on time, anti-
replay may be implemented by discarding any packets that present a SN
whose value is too much in the past. Note that such mechanisms may
consider clock drifting in various ways in addition to acceptable
delay induced by the network to avoid the anti replay windows
rejecting legitimate packets. When a packet is received at a regular
time interval, some variant of time based mechanisms may not even use
the value of the SN, but instead only consider the receiving time of
the packet.
SN can be encoded over 32 bits or 64 bits - known as Extended
Sequence Number (ESN). As per [RFC4303], the support ESN is not
mandatory. The determination of the use of ESN is based on the
largest possible value a SN can take over a session. When SN is
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incremented for each packet, the number of packets sent over the
lifetime of a session may be considered. However, when the SN is
incremented differently - such as when time is used - the maximum
value SN needs to be considered instead. Note that the limit of
messages being sent is primarily determined by the security
associated with the key rather than the SN. The security of all data
protected under a given key decreases slightly with each message and
a node MUST ensure the limit is not reached - even though the SN
would permit it. Estimation of the maximum number of packets to be
sent by a node is always challenging and as such should be considered
cautiously as nodes could be online for much more time than expected.
Even for constrained devices, it is RECOMMENDED to implement some
rekey mechanisms (see Section 10).
5. Padding
The purpose of padding is to respect the 32 bit alignment of ESP or
block size expected by an encryption transform - such as AES-CBC for
example. ESP MUST have at least one padding byte Pad Length that
indicates the padding length. ESP padding bytes are generated by a
succession of unsigned bytes starting with 1, 2, 3 with the last byte
set to Pad Length, where Pad Length designates the length of the
padding bytes.
Checking the padding structure is not mandatory, so the constrained
device may not proceed to such checks, however, in order to
interoperate with existing ESP implementations, it MUST build the
padding bytes as recommended by ESP.
In some situation the padding bytes may take a fix value. This would
typically be the case when the Data Payload is of fix size.
ESP [RFC4303] also provides Traffic Flow Confidentiality (TFC) as a
way to perform padding to hide traffic characteristics, which differs
from respecting a 32 bit alignment. TFC is not mandatory and MUST be
negotiated with the SA management protocol. TFC has not yet being
widely adopted for standard ESP traffic. One possible reason is that
it requires to shape the traffic according to one traffic pattern
that needs to be maintained. This is likely to require extra
processing as well as providing a "well recognized" traffic shape
which could end up being counterproductive. As such, it is NOT
RECOMMENDED that minimal ESP implementation supports TFC.
As a result, TFC cannot be enabled with minimal ESP, and
communication protection that were rely on TFC will be more sensitive
to traffic shaping. This could expose the application as well as the
devices used to a passive monitoring attacker. Such information
could be used by the attacker in case a vulnerability is disclosed on
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the specific device. In addition, some application use - such as
health applications - may also reveal important privacy oriented
information.
Some constrained nodes that have limited battery lifetime may also
prefer avoiding sending extra padding bytes. However, the same nodes
may also be very specific to an application and device. As a result,
they are also likely to be the main target for traffic shaping. In
most cases, the payload carried by these nodes is quite small, and
the standard padding mechanism may also be used as an alternative to
TFC, with a sufficient tradeoff between the require energy to send
additional payload and the exposure to traffic shaping attacks. In
addition, the information leaked by the traffic shaping may also be
addressed by the application level. For example, it is preferred to
have a sensor sending some information at regular time interval,
rather when a specific event is happening. Typically, a sensor
monitoring the temperature, or a door is expected to send regularly
the information - i.e. the temperature of the room or whether the
door is closed or open) instead of only sending the information when
the temperature has raised or when the door is being opened.
6. Next Header (8 bit)
According to [RFC4303], the Next Header is a mandatory 8 bits field
in the packet. Next header specifies the data contained in the
payload as well as dummy packet, i.e. packets with the Next Header
with a value 59 meaning "no next header". In addition, the Next
Header may also carry an indication on how to process the packet
[I-D.nikander-esp-beet-mode].
The ability to generate and receive dummy packet is required by
[RFC4303]. For interoperability, a minimal ESP implementation MUST
discard dummy packets without indicating an error. Note that such
recommendation only applies for nodes receiving packets, and that
nodes designed to only send data may not implement this capability.
As the generation of dummy packets is subject to local management and
based on a per-SA basis, a minimal ESP implementation may not
generate such dummy packet. More especially, in constrained
environment sending dummy packets may have too much impact on the
device lifetime, and so may be avoided. On the other hand,
constrained nodes may be dedicated to specific applications, in which
case, traffic pattern may expose the application or the type of node.
For these nodes, not sending dummy packet may have some privacy
implication that needs to be measured. However, for the same reasons
exposed in Section 5 traffic shaping at the IPsec layer may also
introduce some traffic pattern, and on constrained devices the
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application is probably the most appropriated layer to limit the risk
of leaking information by traffic shaping.
In some cases, devices are dedicated to a single application or a
single transport protocol, in which case, the Next Header has a fix
value.
Specific processing indications have not been standardized yet
[I-D.nikander-esp-beet-mode] and is expected to result from an
agreement between the peers. As a result, it SHOULD NOT be part of a
minimal implementation of ESP.
7. ICV
The ICV depends on the cryptographic suite used. Currently [RFC8221]
only recommends cryptographic suites with an ICV which makes the ICV
a mandatory field.
As detailed in [RFC8221] authentication or authenticated encryption
are RECOMMENDED and as such the ICV field MUST be present with a size
different from zero. It length is defined by the security
recommendations only.
8. Cryptographic Suites
The cryptographic suites implemented are an important component of
ESP. The recommended algorithms to use are expected to evolve over
time and implementers SHOULD follow the recommendations provided by
[RFC8221] and updates.
This section lists some of the criteria that may be considered. The
list is not expected to be exhaustive and may also evolve overtime.
As a result, the list is provided as indicative:
1. Security: Security is the criteria that should be considered
first for the selection of encryption algorithm transform. The
security of encryption algorithm transforms is expected to evolve
over time, and it is of primary importance to follow up-to-date
security guidance and recommendations. The chosen encryption
algorithm MUST NOT be known vulnerable or weak (see [RFC8221] for
outdated ciphers). ESP can be used to authenticate only or to
encrypt the communication. In the latter case, authenticated
encryption must always be considered [RFC8221].
2. Resilience to nonce re-use: Some transforms -including AES-GCM -
are very sensitive to nonce collision with a given key. While
the generation of the nonce may prevent such collision during a
session, the mechanisms are unlikely to provide such protection
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across reboot. This causes an issue for devices that are
configured with a key. When the key is likely to be re-used
across reboots, it is RECOMMENDED to consider algorithms that are
nonce misuse resistant such as, for example, AES-SIV [RFC5297],
AES-GCM-SIV [RFC8452] or Deoxys-II [DeoxysII]. Note however that
currently none of them has yet been defined for ESP.
3. Interoperability: Interoperability considers the encryption
algorithm transforms shared with the other nodes. Note that it
is not because an encryption algorithm transform is widely
deployed that it is secured. As a result, security SHOULD NOT be
weakened for interoperability. [RFC8221] and successors consider
the life cycle of encryption algorithm transforms sufficiently
long to provide interoperability. Constraint devices may have
limited interoperability requirements which makes possible to
reduces the number of encryption algorithm transforms to
implement.
4. Power Consumption and Cipher Suite Complexity: Complexity of the
encryption algorithm transform or the energy associated to it are
especially considered when devices have limited resources or are
using some batteries, in which case the battery determines the
life of the device. The choice of a cryptographic function may
consider re-using specific libraries or to take advantage of
hardware acceleration provided by the device. For example, if
the device benefits from AES hardware modules and uses AES-CTR,
it may prefer AUTH_AES-XCBC for its authentication. In addition,
some devices may also embed radio modules with hardware
acceleration for AES-CCM, in which case, this mode may be
preferred.
5. Power Consumption and Bandwidth Consumption: Similarly to the
encryption algorithm transform complexity, reducing the payload
sent, may significantly reduce the energy consumption of the
device. As a result, encryption algorithm transforms with low
overhead may be considered. To reduce the overall payload size
one may, for example:
1. Use of counter-based ciphers without fixed block length (e.g.
AES-CTR, or ChaCha20-Poly1305).
2. Use of ciphers with capability of using implicit IVs
[RFC8750].
3. Use of ciphers recommended for IoT [RFC8221].
4. Avoid Padding by sending payload data which are aligned to
the cipher block length - 2 for the ESP trailer.
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9. IANA Considerations
There are no IANA consideration for this document.
10. Security Considerations
Security considerations are those of [RFC4303]. In addition, this
document provided security recommendations and guidance over the
implementation choices for each field.
The security of a communication provided by ESP is closely related to
the security associated to the management of that key. This usually
include mechanisms to prevent a nonce to repeat for example. When a
node is provisioned with a session key that is used across reboot,
the implementer MUST ensure that the mechanisms put in place remain
valid across reboot as well.
It is RECOMMENDED to use ESP in conjunction of key management
protocols such as for example IKEv2 [RFC7296] or minimal IKEv2
[RFC7815]. Such mechanisms are responsible to negotiate fresh
session keys as well as prevent a session key being use beyond its
lifetime. When such mechanisms cannot be implemented and the session
key is, for example, provisioned, the nodes MUST ensure that keys are
not used beyond their lifetime and that the appropriate use of the
key remains across reboots - e.g. conditions on counters and nonces
remains valid.
When a node generates its key or when random value such as nonces are
generated, the random generation MUST follow [RFC4086]. In addition
[SP-800-90A-Rev-1] provides appropriated guidance to build random
generators based on deterministic random functions.
11. Acknowledgment
The authors would like to thank Daniel Palomares, Scott Fluhrer, Tero
Kivinen, Valery Smyslov, Yoav Nir, Michael Richardson for their
valuable comments. In particular Scott Fluhrer suggested to include
the rekey index in the SPI as well as the use of transform resilient
to nonce misuse. Tero Kivinen provided also multiple clarifications
and examples of deployment ESP within constrained devices with their
associated optimizations.
12. References
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12.1. 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,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005,
<https://www.rfc-editor.org/info/rfc4086>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, DOI 10.17487/RFC4303, December 2005,
<https://www.rfc-editor.org/info/rfc4303>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <https://www.rfc-editor.org/info/rfc7296>.
[RFC7815] Kivinen, T., "Minimal Internet Key Exchange Version 2
(IKEv2) Initiator Implementation", RFC 7815,
DOI 10.17487/RFC7815, March 2016,
<https://www.rfc-editor.org/info/rfc7815>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8221] Wouters, P., Migault, D., Mattsson, J., Nir, Y., and T.
Kivinen, "Cryptographic Algorithm Implementation
Requirements and Usage Guidance for Encapsulating Security
Payload (ESP) and Authentication Header (AH)", RFC 8221,
DOI 10.17487/RFC8221, October 2017,
<https://www.rfc-editor.org/info/rfc8221>.
[RFC8750] Migault, D., Guggemos, T., and Y. Nir, "Implicit
Initialization Vector (IV) for Counter-Based Ciphers in
Encapsulating Security Payload (ESP)", RFC 8750,
DOI 10.17487/RFC8750, March 2020,
<https://www.rfc-editor.org/info/rfc8750>.
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12.2. Informative References
[DeoxysII]
Jeremy, J., Ivica, I., Thomas, T., and Y. Yannick, "Deoxys
v1.41", October 2016,
<https://competitions.cr.yp.to/round3/deoxysv141.pdf>.
[I-D.mglt-ipsecme-diet-esp]
Migault, D., Guggemos, T., Bormann, C., and D. Schinazi,
"ESP Header Compression and Diet-ESP", draft-mglt-ipsecme-
diet-esp-07 (work in progress), March 2019.
[I-D.mglt-ipsecme-ikev2-diet-esp-extension]
Migault, D., Guggemos, T., and D. Schinazi, "Internet Key
Exchange version 2 (IKEv2) extension for the ESP Header
Compression (EHC) Strategy", draft-mglt-ipsecme-ikev2-
diet-esp-extension-01 (work in progress), June 2018.
[I-D.nikander-esp-beet-mode]
Nikander, P. and J. Melen, "A Bound End-to-End Tunnel
(BEET) mode for ESP", draft-nikander-esp-beet-mode-09
(work in progress), August 2008.
[RFC5297] Harkins, D., "Synthetic Initialization Vector (SIV)
Authenticated Encryption Using the Advanced Encryption
Standard (AES)", RFC 5297, DOI 10.17487/RFC5297, October
2008, <https://www.rfc-editor.org/info/rfc5297>.
[RFC8452] Gueron, S., Langley, A., and Y. Lindell, "AES-GCM-SIV:
Nonce Misuse-Resistant Authenticated Encryption",
RFC 8452, DOI 10.17487/RFC8452, April 2019,
<https://www.rfc-editor.org/info/rfc8452>.
[SP-800-90A-Rev-1]
Elain, E. and J. Kelsey, "Recommendation for Random Number
Generation Using Deterministic Random Bit Generators",
<https://csrc.nist.gov/publications/detail/sp/800-90a/rev-
1/final>.
Authors' Addresses
Daniel Migault
Ericsson
8400 boulevard Decarie
Montreal, QC H4P 2N2
Canada
EMail: daniel.migault@ericsson.com
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Tobias Guggemos
LMU Munich
MNM-Team
Oettingenstr. 67
80538 Munich, Bavaria
Germany
EMail: guggemos@mnm-team.org
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