Network Working Group Y. Nir
Internet-Draft Check Point
Obsoletes: 4307 (if approved) T. Kivinen
Updates: 7296 (if approved) INSIDE Secure
Intended status: Standards Track P. Wouters
Expires: January 21, 2017 Red Hat
D. Migault
Ericsson
July 20, 2016
Algorithm Implementation Requirements and Usage Guidance for IKEv2
draft-ietf-ipsecme-rfc4307bis-10
Abstract
The IPsec series of protocols makes use of various cryptographic
algorithms in order to provide security services. The Internet Key
Exchange (IKE) protocol is used to negotiate the IPsec Security
Association (IPsec SA) parameters, such as which algorithms should be
used. To ensure interoperability between different implementations,
it is necessary to specify a set of algorithm implementation
requirements and usage guidance to ensure that there is at least one
algorithm that all implementations support. This document defines
the current algorithm implementation requirements and usage guidance
for IKEv2 and does minor cleaning up of IKEv2 IANA registry. This
document does not update the algorithms used for packet encryption
using IPsec Encapsulated Security Payload (ESP).
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 http://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 January 21, 2017.
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Copyright Notice
Copyright (c) 2016 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
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Updating Algorithm Implementation Requirements and Usage
Guidance . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Updating Algorithm Requirement Levels . . . . . . . . . . 3
1.3. Document Audience . . . . . . . . . . . . . . . . . . . . 4
2. Conventions Used in This Document . . . . . . . . . . . . . . 5
3. Algorithm Selection . . . . . . . . . . . . . . . . . . . . . 5
3.1. Type 1 - IKEv2 Encryption Algorithm Transforms . . . . . 5
3.2. Type 2 - IKEv2 Pseudo-random Function Transforms . . . . 7
3.3. Type 3 - IKEv2 Integrity Algorithm Transforms . . . . . . 8
3.4. Type 4 - IKEv2 Diffie-Hellman Group Transforms . . . . . 9
4. IKEv2 Authentication . . . . . . . . . . . . . . . . . . . . 10
4.1. IKEv2 Authentication Method . . . . . . . . . . . . . . . 10
4.1.1. Recommendations for RSA key length . . . . . . . . . 11
4.2. Digital Signature Recommendations . . . . . . . . . . . . 12
5. Algorithms for Internet of Things . . . . . . . . . . . . . . 12
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1. Normative References . . . . . . . . . . . . . . . . . . 15
9.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
The Internet Key Exchange (IKE) protocol [RFC7296] is used to
negotiate the parameters of the IPsec SA, such as the encryption and
authentication algorithms and the keys for the protected
communications between the two endpoints. The IKE protocol itself is
also protected by cryptographic algorithms which are negotiated
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between the two endpoints using IKE. Different implementations of
IKE may negotiate different algorithms based on their individual
local policy. To ensure interoperability, a set of "mandatory-to-
implement" IKE cryptographic algorithms is defined.
This document describes the parameters of the IKE protocol and
updates the IKEv2 specification because it changes the mandatory to
implement authentication algorithms of the section 4 of the RFC7296
by saying RSA key lengths of less than 2048 are SHOULD NOT. It does
not describe the cryptographic parameters of the AH or ESP protocols.
1.1. Updating Algorithm Implementation Requirements and Usage Guidance
The field of cryptography evolves continuously. New stronger
algorithms appear and existing algorithms are found to be less secure
then originally thought. Therefore, algorithm implementation
requirements and usage guidance need to be updated from time to time
to reflect the new reality. The choices for algorithms must be
conservative to minimize the risk of algorithm compromise.
Algorithms need to be suitable for a wide variety of CPU
architectures and device deployments ranging from high end bulk
encryption devices to small low-power IoT devices.
The algorithm implementation requirements and usage guidance may need
to change over time to adapt to the changing world. For this reason,
the selection of mandatory-to-implement algorithms was removed from
the main IKEv2 specification and placed in a separate document.
1.2. Updating Algorithm Requirement Levels
The mandatory-to-implement algorithm of tomorrow should already be
available in most implementations of IKE by the time it is made
mandatory. This document attempts to identify and introduce those
algorithms for future mandatory-to-implement status. There is no
guarantee that the algorithms in use today may become mandatory in
the future. Published algorithms are continuously subjected to
cryptographic attack and may become too weak or could become
completely broken before this document is updated.
This document only provides recommendations for the mandatory-to-
implement algorithms or algorithms too weak that are recommended not
to be implemented. As a result, any algorithm listed at the IKEv2
IANA registry not mentioned in this document MAY be implemented. For
clarification and consistency with [RFC4307] an algorithm will be
denoted here as MAY only when it has been downgraded.
Although this document updates the algorithms to keep the IKEv2
communication secure over time, it also aims at providing
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recommendations so that IKEv2 implementations remain interoperable.
IKEv2 interoperability is addressed by an incremental introduction or
deprecation of algorithms. In addition, this document also considers
the new use cases for IKEv2 deployment, such as Internet of Things
(IoT).
It is expected that deprecation of an algorithm is performed
gradually. This provides time for various implementations to update
their implemented algorithms while remaining interoperable. Unless
there are strong security reasons, an algorithm is expected to be
downgraded from MUST to MUST- or SHOULD, instead of MUST NOT.
Similarly, an algorithm that has not been mentioned as mandatory-to-
implement is expected to be introduced with a SHOULD instead of a
MUST.
The current trend toward Internet of Things and its adoption of IKEv2
requires this specific use case to be taken into account as well.
IoT devices are resource constrained devices and their choice of
algorithms are motivated by minimizing the footprint of the code, the
computation effort and the size of the messages to send. This
document indicates "[IoT]" when a specified algorithm is specifically
listed for IoT devices. Requirement levels that are marked as "IoT"
apply to IoT devices and to server-side implementations that might
presumably need to interoperate with them, including any general-
purpose VPN gateways.
1.3. Document Audience
The recommendations of this document mostly target IKEv2 implementers
as implementations need to meet both high security expectations as
well as high interoperability between various vendors and with
different versions. Interoperability requires a smooth move to more
secure cipher suites. This may differ from a user point of view that
may deploy and configure IKEv2 with only the safest cipher suite.
This document does not give any recommendations for the use of
algorithms, it only gives implementation recommendations for
implementations. The use of algorithms by users is dictated by the
security policy requirements for that specific user, and are outside
the scope of this document.
IKEv1 is out of scope of this document. IKEv1 is deprecated and the
recommendations of this document must not be considered for IKEv1, as
most IKEv1 implementations have been "frozen" and will not be able to
update the list of mandatory-to-implement algorithms.
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2. Conventions Used in This Document
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].
We define some additional terms here:
SHOULD+ This term means the same as SHOULD. However, it is likely
that an algorithm marked as SHOULD+ will be promoted at
some future time to be a MUST.
SHOULD- This term means the same as SHOULD. However, an algorithm
marked as SHOULD- may be deprecated to a MAY in a future
version of this document.
MUST- This term means the same as MUST. However, we expect at
some point that this algorithm will no longer be a MUST in
a future document. Although its status will be determined
at a later time, it is reasonable to expect that if a
future revision of a document alters the status of a MUST-
algorithm, it will remain at least a SHOULD or a SHOULD-
level.
IoT stands for Internet of Things.
3. Algorithm Selection
3.1. Type 1 - IKEv2 Encryption Algorithm Transforms
The algorithms in the below table are negotiated in the SA payload
and used for the Encrypted Payload. References to the specification
defining these algorithms and the ones in the following subsections
are in the IANA registry [IKEV2-IANA]. Some of these algorithms are
Authenticated Encryption with Associated Data (AEAD - [RFC5282]).
Algorithms that are not AEAD MUST be used in conjunction with an
integrity algorithms in Section 3.3.
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+------------------------+----------+-------+----------+
| Name | Status | AEAD? | Comment |
+------------------------+----------+-------+----------+
| ENCR_AES_CBC | MUST | No | [1] |
| ENCR_CHACHA20_POLY1305 | SHOULD | Yes | |
| ENCR_AES_GCM_16 | SHOULD | Yes | [1] |
| ENCR_AES_CCM_8 | SHOULD | Yes | [1][IoT] |
| ENCR_3DES | MAY | No | |
| ENCR_DES | MUST NOT | No | |
+------------------------+----------+-------+----------+
[1] - This requirement level is for 128-bit keys. 256-bit keys are at
SHOULD. 192-bit keys can safely be ignored. [IoT] - This requirement
is for interoperability with IoT.
ENCR_AES_CBC is raised from SHOULD+ in [RFC4307] to MUST. It is the
only shared mandatory-to-implement algorithm with RFC4307 and as a
result it is necessary for interoperability with IKEv2 implementation
compatible with RFC4307.
ENCR_CHACHA20_POLY1305 was not ready to be considered at the time of
RFC4307. It has been recommended by the CRFG and others as an
alternative to AES-CBC and AES-GCM. It is also being standardized
for IPsec for the same reasons. At the time of writing, there were
not enough IKEv2 implementations supporting ENCR_CHACHA20_POLY1305 to
be able to introduce it at the SHOULD+ level.
ENCR_AES_GCM_16 was not considered in RFC4307. At the time RFC4307
was written, AES-GCM was not defined in an IETF document. AES-GCM
was defined for ESP in [RFC4106] and later for IKEv2 in [RFC5282].
The main motivation for adopting AES-GCM for ESP is encryption
performance and key longevity compared to AES-CBC. This resulted in
AES-GCM being widely implemented for ESP. As the computation load of
IKEv2 is relatively small compared to ESP, many IKEv2 implementations
have not implemented AES-GCM. For this reason, AES-GCM is not
promoted to a greater status than SHOULD. The reason for promotion
from MAY to SHOULD is to promote the slightly more secure AEAD method
over the traditional encrypt+auth method. Its status is expected to
be raised once widely implemented. As the advantage of the shorter
(and weaker) ICVs is minimal, the 8 and 12 octet ICV's remain at the
MAY level.
ENCR_AES_CCM_8 was not considered in RFC4307. This document
considers it as SHOULD be implemented in order to be able to interact
with Internet of Things devices. As this case is not a general use
case for non-IoT VPNs, its status is expected to remain as SHOULD.
The 8 octet size of the ICV is expected to be sufficient for most use
cases of IKEv2, as far less packets are exchanged on those cases, and
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IoT devices want to make packets as small as possible. When
implemented, ENCR_AES_CCM_8 MUST be implemented for key length 128
and MAY be implemented for key length 256.
ENCR_3DES has been downgraded from RFC4307 MUST- to SHOULD NOT. All
IKEv2 implementation already implement ENCR_AES_CBC, so there is no
need to keep support for the much slower ENCR_3DES. In addition,
ENCR_CHACHA20_POLY1305 provides a more modern alternative to AES.
ENCR_DES can be brute-forced using of-the-shelves hardware. It
provides no meaningful security whatsoever and therefor MUST NOT be
implemented.
3.2. Type 2 - IKEv2 Pseudo-random Function Transforms
Transform Type 2 algorithms are pseudo-random functions used to
generate pseudo-random values when needed.
If an algorithm is selected as the integrity algorithm, it SHOULD
also be used as the PRF. When using an AEAD cipher, a choice of PRF
needs to be made. The table below lists the recommended algorithms.
+-------------------+----------+---------+
| Name | Status | Comment |
+-------------------+----------+---------+
| PRF_HMAC_SHA2_256 | MUST | |
| PRF_HMAC_SHA2_512 | SHOULD+ | |
| PRF_HMAC_SHA1 | MUST- | |
| PRF_AES128_XCBC | SHOULD | [IoT] |
| PRF_HMAC_MD5 | MUST NOT | |
+-------------------+----------+---------+
[IoT] - This requirement is for interoperability with IoT
PRF_HMAC_SHA2_256 was not mentioned in RFC4307, as no SHA2 based
transforms were mentioned. PRF_HMAC_SHA2_256 MUST be implemented in
order to replace SHA1 and PRF_HMAC_SHA1.
PRF_HMAC_SHA2_512 SHOULD be implemented as a future replacement for
PRF_HMAC_SHA2_256 or when stronger security is required.
PRF_HMAC_SHA2_512 is preferred over PRF_HMAC_SHA2_384, as the
additional overhead of PRF_HMAC_SHA2_512 is negligible.
PRF_HMAC_SHA1 has been downgraded from MUST in RFC4307 to MUST- as
their is an industry-wide trend to deprecate its usage.
PRF_AES128_XCBC is only recommended in the scope of IoT, as Internet
of Things deployments tend to prefer AES based pseudo-random
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functions in order to avoid implementing SHA2. For the non-IoT VPN
deployment it has been downgraded from SHOULD in RFC4307 to MAY as it
has not seen wide adoption.
PRF_HMAC_MD5 has been downgraded from MAY in RFC4307 to MUST NOT.
There is an industry-wide trend to deprecate its usage as MD5 support
is being removed from cryptographic libraries in general because its
non-HMAC use is known to be subject to collision attacks, for example
as mentioned in [TRANSCRIPTION].
3.3. Type 3 - IKEv2 Integrity Algorithm Transforms
The algorithms in the below table are negotiated in the SA payload
and used for the Encrypted Payload. References to the specification
defining these algorithms are in the IANA registry. When an AEAD
algorithm (see Section 3.1) is proposed, this algorithm transform
type is not in use.
+------------------------+----------+---------+
| Name | Status | Comment |
+------------------------+----------+---------+
| AUTH_HMAC_SHA2_256_128 | MUST | |
| AUTH_HMAC_SHA2_512_256 | SHOULD | |
| AUTH_HMAC_SHA1_96 | MUST- | |
| AUTH_AES_XCBC_96 | SHOULD | [IoT] |
| AUTH_HMAC_MD5_96 | MUST NOT | |
| AUTH_DES_MAC | MUST NOT | |
| AUTH_KPDK_MD5 | MUST NOT | |
+------------------------+----------+---------+
[IoT] - This requirement is for interoperability with IoT
AUTH_HMAC_SHA2_256_128 was not mentioned in RFC4307, as no SHA2 based
transforms were mentioned. AUTH_HMAC_SHA2_256_128 MUST be
implemented in order to replace AUTH_HMAC_SHA1_96.
AUTH_HMAC_SHA2_512_256 SHOULD be implemented as a future replacement
of AUTH_HMAC_SHA2_256_128 or when stronger security is required.
This value has been preferred over AUTH_HMAC_SHA2_384, as the
additional overhead of AUTH_HMAC_SHA2_512 is negligible.
AUTH_HMAC_SHA1_96 has been downgraded from MUST in RFC4307 to MUST-
as there is an industry-wide trend to deprecate its usage.
AUTH_AES-XCBC is only recommended in the scope of IoT, as Internet of
Things deployments tend to prefer AES based pseudo-random functions
in order to avoid implementing SHA2. For the non-IoT VPN deployment,
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it has been downgraded from SHOULD in RFC4307 to MAY as it has not
been widely adopted.
AUTH_DES_MAC, AUTH_HMAC_MD5_96, and AUTH_KPDK_MD5 were not mentioned
in RFC4307 so their default status ware MAY. They have been
downgraded to MUST NOT. There is an industry-wide trend to deprecate
DES and MD5. MD5 support is being removed from cryptographic
libraries in general because its non-HMAC use is known to be subject
to collision attacks, for example as mentioned in [TRANSCRIPTION].
3.4. Type 4 - IKEv2 Diffie-Hellman Group Transforms
There are several Modular Exponential (MODP) groups and several
Elliptic Curve groups (ECC) that are defined for use in IKEv2. These
groups are defined in both the [IKEv2] base document and in
extensions documents and are identified by group number. Note that
it is critical to enforce a secure Diffie-Hellman exchange as this
exchange provides keys for the session. If an attacker can retrieve
the private numbers (a, or b) and the public values (g**a, and g**b),
then the attacker can compute the secret and the keys used and
decrypt the exchange and IPsec SA created inside the IKEv2 SA. Such
an attack can be performed off-line on a previously recorded
communication, years after the communication happened. This differs
from attacks that need to be executed during the authentication which
must be performed online and in near real-time.
+--------+---------------------------------------------+------------+
| Number | Description | Status |
+--------+---------------------------------------------+------------+
| 14 | 2048-bit MODP Group | MUST |
| 19 | 256-bit random ECP group | SHOULD |
| 5 | 1536-bit MODP Group | SHOULD NOT |
| 2 | 1024-bit MODP Group | SHOULD NOT |
| 1 | 768-bit MODP Group | MUST NOT |
| 22 | 1024-bit MODP Group with 160-bit Prime | SHOULD NOT |
| | Order Subgroup | |
| 23 | 2048-bit MODP Group with 224-bit Prime | SHOULD NOT |
| | Order Subgroup | |
| 24 | 2048-bit MODP Group with 256-bit Prime | SHOULD NOT |
| | Order Subgroup | |
+--------+---------------------------------------------+------------+
Group 14 or 2048-bit MODP Group is raised from SHOULD+ in RFC4307 as
a replacement for 1024-bit MODP Group. Group 14 is widely
implemented and considered secure.
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Group 19 or 256-bit random ECP group was not specified in RFC4307, as
this group were not specified at that time. Group 19 is widely
implemented and considered secure.
Group 5 or 1536-bit MODP Group has been downgraded from MAY in
RFC4307 to SHOULD NOT. It was specified earlier, but is now
considered to be vulnerable to be broken within the next few years by
a nation state level attack, so its security margin is considered too
narrow.
Group 2 or 1024-bit MODP Group has been downgraded from MUST- in
RFC4307 to SHOULD NOT. It is known to be weak against sufficiently
funded attackers using commercially available mass-computing
resources, so its security margin is considered too narrow. It is
expected in the near future to be downgraded to MUST NOT.
Group 1 or 768-bit MODP Group was not mentioned in RFC4307 and so its
status was MAY. It can be broken within hours using cheap of-the-
shelves hardware. It provides no security whatsoever.
Group 22, 23 and 24 or 1024-bit MODP Group with 160-bit, and 2048-bit
MODP Group with 224-bit and 256-bit Prime Order Subgroup have small
subgroups, which means that checks specified in the "Additional
Diffie-Hellman Test for the IKEv2" [RFC6989] section 2.2 first bullet
point MUST be done when these groups are used. These groups are also
not safe-primes. The seeds for these groups have not been publicly
released, resulting in reduced trust in these groups. These groups
were proposed as alternatives for group 2 and 14 but never saw wide
deployment. It is expected in the near future to be further
downgraded to MUST NOT.
4. IKEv2 Authentication
IKEv2 authentication may involve a signatures verification.
Signatures may be used to validate a certificate or to check the
signature of the AUTH value. Cryptographic recommendations regarding
certificate validation are out of scope of this document. What is
mandatory to implement is provided by the PKIX Community. This
document is mostly concerned on signature verification and generation
for the authentication.
4.1. IKEv2 Authentication Method
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+--------+---------------------------------------+------------+
| Number | Description | Status |
+--------+---------------------------------------+------------+
| 1 | RSA Digital Signature | MUST |
| 2 | Shared Key Message Integrity Code | MUST |
| 3 | DSS Digital Signature | SHOULD NOT |
| 9 | ECDSA with SHA-256 on the P-256 curve | SHOULD |
| 10 | ECDSA with SHA-384 on the P-384 curve | SHOULD |
| 11 | ECDSA with SHA-512 on the P-521 curve | SHOULD |
| 14 | Digital Signature | SHOULD |
+--------+---------------------------------------+------------+
RSA Digital Signature is widely deployed and therefore kept for
interoperability. It is expected to be downgraded in the future as
its signatures are based on the older RSASSA-PKCS1-v1.5 which is no
longer recommended. RSA authentication, as well as other specific
Authentication Methods, are expected to be replaced with the generic
Digital Signature method of [RFC7427]. RSA Digital Signature is not
recommended for keys smaller then 2048, but since these signatures
only have value in real-time, and need no future protection, smaller
keys was kept at SHOULD NOT instead of MUST NOT.
Shared Key Message Integrity Code is widely deployed and mandatory to
implement in the IKEv2 in the RFC7296.
ECDSA based Authentication Methods are also expected to be downgraded
as it does not provide hash function agility. Instead, ECDSA (like
RSA) is expected to be performed using the generic Digital Signature
method.
DSS Digital Signature is bound to SHA-1 and has the same level of
security as 1024-bit RSA. It is expected to be downgraded to MUST
NOT in the future.
Digital Signature [RFC7427] is expected to be promoted as it provides
hash function, signature format and algorithm agility.
4.1.1. Recommendations for RSA key length
+-------------------------------------------+------------+
| Description | Status |
+-------------------------------------------+------------+
| RSA with key length 2048 | MUST |
| RSA with key length 3072 and 4096 | SHOULD |
| RSA with key length between 2049 and 4095 | MAY |
| RSA with key length smaller than 2048 | SHOULD NOT |
+-------------------------------------------+------------+
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The IKEv2 RFC7296 mandates support for the RSA keys of size 1024 or
2048 bits, but here we make key sizes less than 2048 SHOULD NOT as
there is industry-wide trend to deprecate key lengths less than 2048
bits.
4.2. Digital Signature Recommendations
When Digital Signature authentication method is implemented, then the
following recommendations are applied for hash functions:
+--------+-------------+----------+---------+
| Number | Description | Status | Comment |
+--------+-------------+----------+---------+
| 1 | SHA1 | MUST NOT | |
| 2 | SHA2-256 | MUST | |
| 3 | SHA2-384 | MAY | |
| 4 | SHA2-512 | SHOULD | |
+--------+-------------+----------+---------+
When Digital Signature authentication method is used with RSA
signature algorithm, then RSASSA-PSS MUST be supported and RSASSA-
PKCS1-v1.5 MAY be supported.
The following table lists recommendations for authentication methods
in RFC7427 [RFC7427] notation. These recommendations are applied
only if Digital Signature authentication method is implemented.
+------------------------------------+----------+---------+
| Description | Status | Comment |
+------------------------------------+----------+---------+
| RSASSA-PSS with SHA-256 | MUST | |
| ecdsa-with-sha256 | SHOULD | |
| sha1WithRSAEncryption | MUST NOT | |
| dsa-with-sha1 | MUST NOT | |
| ecdsa-with-sha1 | MUST NOT | |
| RSASSA-PSS with Empty Parameters | MUST NOT | |
| RSASSA-PSS with Default Parameters | MUST NOT | |
+------------------------------------+----------+---------+
5. Algorithms for Internet of Things
Some algorithms in this document are marked for use with the Internet
of Things (IoT). There are several reasons why IoT devices prefer a
different set of algorithms from regular IKEv2 clients. IoT devices
are usually very constrained, meaning the memory size and CPU power
is so limited, that these clients only have resources to implement
and run one set of algorithms. For example, instead of implementing
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AES and SHA, these devices typically use AES_XCBC as integrity
algorithm so SHA does not need to be implemented.
For example, IEEE Std 802.15.4 [IEEE-802-15-4] devices have a
mandatory to implement link level security using AES-CCM with 128 bit
keys. The IEEE Recommended Practice for Transport of Key Management
Protocol (KMP) Datagrams [IEEE-802-15-9] already provide a way to use
Minimal IKEv2 [RFC7815] over 802.15.4 to provide link keys for the
802.15.4 layer.
These devices might want to use AES-CCM as their IKEv2 algorithm, so
they can reuse the hardware implementing it. They cannot use the
AES-CBC algorithm, as the hardware quite often do not include support
for AES decryption needed to support the CBC mode. So despite the
AES-CCM algorithm requiring AEAD [RFC5282] support, the benefit of
reusing the crypto hardware makes AES-CCM the preferred algorithm.
Another important aspect of IoT devices is that their transfer rates
are usually quite low (in order of tens of kbits/s), and each bit
they transmit has an energy consumption cost associated with it and
shortens their battery life. Therefore, shorter packets are
preferred. This is the reason for recommending the 8 octet ICV over
the 16 octet ICV.
Because different IoT devices will have different constraints, this
document cannot specify the one mandatory profile for IoT. Instead,
this document points out commonly used algorithms with IoT devices.
6. Security Considerations
The security of cryptographic-based systems depends on both the
strength of the cryptographic algorithms chosen and the strength of
the keys used with those algorithms. The security also depends on
the engineering of the protocol used by the system to ensure that
there are no non-cryptographic ways to bypass the security of the
overall system.
The Diffie-Hellman Group parameter is the most important one to
choose conservatively. Any party capturing all IKE and ESP traffic
that (even years later) can break the selected DH group in IKE, can
gain access to the symmetric keys used to encrypt all the ESP
traffic. Therefore, these groups must be chosen very conservatively.
However, specifying an extremely large DH group also puts a
considerable load on the device, especially when this is a large VPN
gateway or an IoT constrained device.
This document concerns itself with the selection of cryptographic
algorithms for the use of IKEv2, specifically with the selection of
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"mandatory-to-implement" algorithms. The algorithms identified in
this document as "MUST implement" or "SHOULD implement" are not known
to be broken at the current time, and cryptographic research so far
leads us to believe that they will likely remain secure into the
foreseeable future. However, this isn't necessarily forever and it
is expected that new revisions of this document will be issued from
time to time to reflect the current best practice in this area.
7. IANA Considerations
This document renames some of the names in the "Transform Type 1 -
Encryption Algorithm Transform IDs" registry of the "Internet Key
Exchange Version 2 (IKEv2) Parameters". All the other names have
ENCR_ prefix except 3, and all other entries use names in format of
uppercase words separated with underscores except 6. This document
changes those names to match others.
This document requests IANA to rename following entries:
+---------------------------------------+----------------------+
| Old name | New name |
+---------------------------------------+----------------------+
| AES-GCM with a 8 octet ICV | ENCR_AES_GCM_8 |
| AES-GCM with a 12 octet ICV | ENCR_AES_GCM_12 |
| AES-GCM with a 16 octet ICV | ENCR_AES_GCM_16 |
| ENCR_CAMELLIA_CCM with an 8-octet ICV | ENCR_CAMELLIA_CCM_8 |
| ENCR_CAMELLIA_CCM with a 12-octet ICV | ENCR_CAMELLIA_CCM_12 |
| ENCR_CAMELLIA_CCM with a 16-octet ICV | ENCR_CAMELLIA_CCM_16 |
+---------------------------------------+----------------------+
In addition to add this RFC as reference to both ESP Reference and
IKEv2 Reference columns for ENCR_AES_GCM entries, keeping the current
references there also, and also add this RFC as reference to the ESP
Reference column for ENCR_CAMELLIA_CCM entries, keeping the current
reference there also.
The final registry entries should be:
Number Name ESP Reference IKEv2 Reference
...
18 ENCR_AES_GCM_8 [RFC4106][RFCXXXX] [RFC5282][RFCXXXX]
19 ENCR_AES_GCM_12 [RFC4106][RFCXXXX] [RFC5282][RFCXXXX]
20 ENCR_AES_GCM_16 [RFC4106][RFCXXXX] [RFC5282][RFCXXXX]
...
25 ENCR_CAMELLIA_CCM_8 [RFC5529][RFCXXXX] -
26 ENCR_CAMELLIA_CCM_12 [RFC5529][RFCXXXX] -
27 ENCR_CAMELLIA_CCM_16 [RFC5529][RFCXXXX] -
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8. Acknowledgements
The first version of this document was RFC 4307 by Jeffrey I.
Schiller of the Massachusetts Institute of Technology (MIT). Much of
the original text has been copied verbatim.
We would like to thank Paul Hoffman, Yaron Sheffer, John Mattsson and
Tommy Pauly for their valuable feedback.
9. References
9.1. 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,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode
(GCM) in IPsec Encapsulating Security Payload (ESP)",
RFC 4106, DOI 10.17487/RFC4106, June 2005,
<http://www.rfc-editor.org/info/rfc4106>.
[RFC4307] Schiller, J., "Cryptographic Algorithms for Use in the
Internet Key Exchange Version 2 (IKEv2)", RFC 4307,
DOI 10.17487/RFC4307, December 2005,
<http://www.rfc-editor.org/info/rfc4307>.
[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, <http://www.rfc-editor.org/info/rfc7296>.
[RFC5282] Black, D. and D. McGrew, "Using Authenticated Encryption
Algorithms with the Encrypted Payload of the Internet Key
Exchange version 2 (IKEv2) Protocol", RFC 5282,
DOI 10.17487/RFC5282, August 2008,
<http://www.rfc-editor.org/info/rfc5282>.
9.2. Informative References
[RFC7427] Kivinen, T. and J. Snyder, "Signature Authentication in
the Internet Key Exchange Version 2 (IKEv2)", RFC 7427,
DOI 10.17487/RFC7427, January 2015,
<http://www.rfc-editor.org/info/rfc7427>.
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[RFC6989] Sheffer, Y. and S. Fluhrer, "Additional Diffie-Hellman
Tests for the Internet Key Exchange Protocol Version 2
(IKEv2)", RFC 6989, DOI 10.17487/RFC6989, July 2013,
<http://www.rfc-editor.org/info/rfc6989>.
[RFC7815] Kivinen, T., "Minimal Internet Key Exchange Version 2
(IKEv2) Initiator Implementation", RFC 7815,
DOI 10.17487/RFC7815, March 2016,
<http://www.rfc-editor.org/info/rfc7815>.
[IKEV2-IANA]
"Internet Key Exchange Version 2 (IKEv2) Parameters",
<http://www.iana.org/assignments/ikev2-parameters>.
[TRANSCRIPTION]
Bhargavan, K. and G. Leurent, "Transcript Collision
Attacks: Breaking Authentication in TLS, IKE, and SSH",
NDSS , feb 2016.
[IEEE-802-15-4]
"IEEE Standard for Low-Rate Wireless Personal Area
Networks (WPANs)", IEEE Standard 802.15.4, 2015.
[IEEE-802-15-9]
"IEEE Recommended Practice for Transport of Key Management
Protocol (KMP) Datagrams", IEEE Standard 802.15.9, 2016.
Authors' Addresses
Yoav Nir
Check Point Software Technologies Ltd.
5 Hasolelim st.
Tel Aviv 6789735
Israel
EMail: ynir.ietf@gmail.com
Tero Kivinen
INSIDE Secure
Eerikinkatu 28
HELSINKI FI-00180
FI
EMail: kivinen@iki.fi
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Paul Wouters
Red Hat
EMail: pwouters@redhat.com
Daniel Migault
Ericsson
8400 boulevard Decarie
Montreal, QC H4P 2N2
Canada
Phone: +1 514-452-2160
EMail: daniel.migault@ericsson.com
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