6lo D. Migault, Ed.
Internet-Draft Ericsson
Intended status: Standards Track T. Guggemos, Ed.
Expires: August 21, 2015 LMU Munich
February 17, 2015
Requirements for Diet-ESP the IPsec/ESP protocol for IoT
draft-mglt-6lo-diet-esp-requirements-01.txt
Abstract
IPsec/ESP is used to secure end-to-end communications. This document
lists the requirements Diet-ESP should meet to design IPsec/ESP for
IoT.
Status of This Memo
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Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Protocol Design . . . . . . . . . . . . . . . . . . . . . . . 3
5. Byte-Alignment . . . . . . . . . . . . . . . . . . . . . . . 3
6. Crypto-Suites . . . . . . . . . . . . . . . . . . . . . . . . 4
7. Compression . . . . . . . . . . . . . . . . . . . . . . . . . 4
8. Flexibility . . . . . . . . . . . . . . . . . . . . . . . . . 5
9. Code Complexity . . . . . . . . . . . . . . . . . . . . . . . 5
10. Usability . . . . . . . . . . . . . . . . . . . . . . . . . . 5
11. Compatibility with IP compression Protocols . . . . . . . . . 6
12. Compatibility with Standard ESP . . . . . . . . . . . . . . . 6
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
14. Security Considerations . . . . . . . . . . . . . . . . . . . 6
15. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 6
16. Normative References . . . . . . . . . . . . . . . . . . . . 7
Appendix A. Power Consumption Example . . . . . . . . . . . . . 7
Appendix B. Document Change Log . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Requirements notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Introduction
IoT devices can carry all kind of small applications and some of them
require a secure communication. They can be life critical devices
(like a fire alarm), security critical devices (like home theft
alarms) and home automation devices. Smart grid is one application
where supplied electricity is based on information provided by each
home. Similarly, home temperature might be determined by servo-
controls based on information provided by temperature sensors.
Using IPsec [RFC4301] in the IoT world provides some advantages, such
as:
- IPsec secures application communications transparently as security
is handled at the IP layer. As such, applications do not need to
be modified to be secured.
- IPsec does not depend on the transport layer. As a result, the
security framework remains the same for all transport protocols,
like UDP or TCP.
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- IPsec is well designed for sleeping nodes as there are no
sessions.
- IPsec defines security rules for the whole device, which outsource
the device security to a designated area. Therefore IPsec can be
seen like a tiny firewall securing all communication for an IoT
device.
IPsec is mostly implemented in the kernel, whereas application are in
the user space. This is often considered as a disadvantage for
IPsec. However, as there are no real distinctions between these two
spaces in IoT and that IoT devices are mostly designed to a specific
and unique task, this may not be an issue anymore.
IoT constraints have not been considered in the early design of
IPsec. In fact IPsec has mainly been designed to secure
infrastructure. This document describes the requirements of Diet-
ESP, the declination of IPsec/ESP for IoT, enabling optimized IPsec/
ESP for the IoT.
3. Terminology
- IoT: Internet of Things
4. Protocol Design
Diet-ESP is based on IPsec/ESP and is adapted for IoT. Adaptation to
IoT scenarios must not be at the expense of security, and the
security evaluation of Diet-ESP should benefit as far as possible
from the long experience of already existing protocols. As a result
the protocol design requirements for Diet-ESP are as follows:
R1: Diet-ESP MUST benefit from the IPsec/ESP security.
R2: Diet-ESP MUST NOT introduce vulnerabilities over IPsec/ESP.
This means that at some points IPsec/ESP is implemented. A
foreseen way to reach that goal is to associate IPsec/ESP with
compressors/decompressors.
R3: Diet-ESP SHOULD rely on existing protocol or frameworks.
5. Byte-Alignment
IP extension headers MUST have 32 bit Byte-Alignment in IPv4 (section
3.1 of [RFC0791] - Padding description) and a 64 bit Byte-Alignment
in IPv6 (section 4 of [RFC2460]). As ESP [RFC4303] is such an
extension header, padding is mandatory to meet the alignment
constraint. This alignment is mostly caused by compiler and OS
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requirements dealing with a 32 or 64 Bit processor. In the world of
IoT, processors and compilers are highly specialized and alignment is
often not necessary 32 Bit, but 16 or 8 bit. As a result, the byte-
alignment requirement is as follows:
R4: Diet-ESP MUST support Byte-Alignment that are different from 32
bits or 64 bits to prevent unnecessary padding.
R5: Each peer MUST be able to advertise and negotiate the Byte-
Alignment, used for Diet-ESP. This could be done for example
during the IKEv2 exchange.
6. Crypto-Suites
IEEE 802.15.4 defines AES-CCM*, that is AES-CTR and CBC-MAC, for link
layer security with upper layer key-management. Therefore it is
usually supported by hardware acceleration. This leads to the
following crypto-suite requirement:
R6: Diet-ESP MUST support AES-CCM and MUST be able to take advantage
of AES-CCM hardware acceleration. Diet-ESP MAY support other
modes.
7. Compression
Sending data is very expensive regarding to power consumption, as
illustrated in Appendix A. Compression can be performed at different
layers. An encrypted ESP packet is an ESP Clear Text Data encrypted
and eventually concatenated with the Initialization Vector IV to form
an Encrypted Data Payload. This encrypted Data Payload is then
placed between an ESP Header and an ESP Trailer. Eventually, this
packet is authenticated with an ICV appended to ESP Trailer.
Compression can be performed at the ESP layer that is to say for the
fields of the ESP Header, ESP Trailer and the ICV. In addition, ESP
Clear Text Data may also be compressed with non ESP mechanisms like
ROHC [RFC3095], [RFC5225] for example, resulting in a smaller payload
to be encrypted. If ESP is using encryption, these mechanisms MUST
be performed over the ESP Clear Text Data before the ESP/Diet-ESP
processing as missing of encrypted fields make decryption harder. As
a result, compression requirements are as follows:
R7: Diet-ESP MUST be able to compress/remove all static ESP fields
(SPI, Next Header) as well as the other fields SN, Padding, Pad
Length or ICV.
R8: Diet-ESP SHOULD also allow compression mechanisms before the
IPsec/ESP processing.
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R9: Diet-ESP SHOULD NOT allow compressed fields, not aligned to 1
byte in order to prevent alignment complexity. In other words,
Diet-ESP do not consider finer granularity than the byte.
8. Flexibility
Diet-ESP can compress some of the ESP fields as Diet-ESP is optimized
for IoT. Which field may be compressed or not, depends on the
scenario and current and future scenarios cannot been foreseen. As a
result, the flexibility requirements are as follows:
R10: Diet-ESP MUST be able to compress any field independently from
another.
R11: Diet-ESP SHOULD provide different ways to compress a single
field, so the most appropriated way can be agreed between the
peers.
R12: Each peer MUST be able to announce and negotiate the different
compressed fields as well as the used method.
In fact Diet-ESP and ESP differs in the following point: ESP has been
designed so that any ESP secured communication so any device is able
to communicate with another. This means that ESP has been designed
to work for large Security Gateway under thousands of connections, as
well as devices with a single ESP communication. Because, ESP has
been designed not to introduce any protocol limitations, counters and
identifiers may become over-sized in an IoT context.
9. Code Complexity
IoT devices have limited space for memory and storage, which leads to
the following requirement.
R13: Diet-ESP MUST be able to be implemented with minimal complexity.
More especially, Diet-ESP MUST consider small implementation
that implement only a subset of all Diet-ESP capabilities
without requiring involving standard ESP, specific compressors
and de-compressors.
10. Usability
Application Developer usually do not want to take care about the
underlying protocols and security. In addition, the security
configuration should remain feasible by a standard software
developer. The usability requirements regarding Diet-ESP are as
follows:
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R14: Diet-ESP MUST remain independent from the application.
R15: Diet-ESP MUST detail for each field how compression impacts the
security of the device. Although the creation of profiles is
out of scope of Diet-ESP, it is expected that profiles may be
defined latter by the usage.
11. Compatibility with IP compression Protocols
There are different protocols providing IP layer compression for
constraint devices like IoT (6LoWPAN [RFC6282] ) or Mobile Devices
(ROHC). The requirements regarding interactions of Diet-ESP and
additional compression protocols are as follows:
R16: Diet-ESP MUST be able to interact with IP compression protocols.
More especially, this means that a Diet-ESP packet MUST be able
to be sent in a ROHC or a 6LowPAN packet. Diet-ESP document
should explicitly detail how this can be achieved.
R17: Diet-ESP MUST also detail how compression of layers above IP
with ROHC or 6LowPAN is compatible with Diet-ESP.
12. Compatibility with Standard ESP
IPsec/ESP is widely deployed by different vendors on different
machines. IoT devices MAY have to communicate with Standard ESP
implementations. The ESP compatibility requirements is as follows:
R18: Diet-ESP MUST be able to communicate with Standard ESP.
13. IANA Considerations
There are no IANA consideration for this document.
14. Security Considerations
Security Considerations have been expressed as one of the
requirement.
15. Acknowledgment
The current work on Diet-ESP results from exchange and cooperation
between Orange, Ludwig-Maximilians-Universitaet Munich, Universite
Pierre et Marie Curie. We thank Daniel Palomares and Carsten Bormann
for their useful remarks, comments and guidances on the design. We
thank Sylvain Killian for implementing an open source Diet-ESP on
Contiki and testing it on the FIT IoT-LAB [fit-iot-lab] funded by the
French Ministry of Higher Education and Research. We thank the IoT-
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Lab Team and the INRIA for maintaining the FIT IoT-LAB platform and
for providing feed backs in an efficient way.
16. Normative References
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September
1981.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC3095] Bormann, C., Burmeister, C., Degermark, M., Fukushima, H.,
Hannu, H., Jonsson, L-E., Hakenberg, R., Koren, T., Le,
K., Liu, Z., Martensson, A., Miyazaki, A., Svanbro, K.,
Wiebke, T., Yoshimura, T., and H. Zheng, "RObust Header
Compression (ROHC): Framework and four profiles: RTP, UDP,
ESP, and uncompressed", RFC 3095, July 2001.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC
4303, December 2005.
[RFC5225] Pelletier, G. and K. Sandlund, "RObust Header Compression
Version 2 (ROHCv2): Profiles for RTP, UDP, IP, ESP and
UDP-Lite", RFC 5225, April 2008.
[RFC6282] Hui, J. and P. Thubert, "Compression Format for IPv6
Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
September 2011.
[fit-iot-lab]
"Future Internet of Things (FIT) IoT-LAB",
<https://www.iot-lab.info>.
Appendix A. Power Consumption Example
IoT devices are often installed once and left untouched for a couple
of years. Furthermore they often do not have a power supply
wherefore they have to be fueled by a battery. This battery may have
a limited capacity and maybe not replaceable. Therefore, power can
be a limited resource in the world of IoT. Table 1 and Table 2 shows
the costs for transmitting data and computation
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Note these data are mentioned here with an illustrative purpose, for
our motivations. These data may vary from one device to another, and
may change over time.
+-------------------------+---------------------+
| | power consumption |
+-------------------------+---------------------+
| low-power radios < 10mW | (100nJ - 1uJ) / bit |
+-------------------------+---------------------+
Table 1: Power consumption for data transmission.
+----------------------------------+---------------------+
| | power consumption |
+----------------------------------+---------------------+
| energy-efficient microprocessors | 0.5nJ / instruction |
| high-performance microprocessors | 200nJ / instruction |
+----------------------------------+---------------------+
Table 2: Power consumption for computation.
From these tables, sending 1 bit costs as much as 10-100 instructions
in the CPU. Therefore there is a high interest to reduce the number
of bits sent on the wire, even if it generates costs for computation.
Appendix B. Document Change Log
[draft-mglt-6lo-diet-esp-requirements-01.txt]: Changing affiliation.
[draft-mglt-6lo-diet-esp-requirements-00.txt]: Published: Minor re-
wordings
[draft-mglt-ipsecme-diet-ipsec-requirements-00.txt]: First version
published.
Authors' Addresses
Daniel Migault (editor)
Ericsson
8400 boulevard Decarie
Montreal, QC H4P 2N2
Canada
Email: mglt.ietf@gmail.com
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Tobias Guggemos (editor)
LMU Munich
Am Osteroesch 9
87637 Seeg, Bavaria
Germany
Email: tobias.guggemos@gmail.com
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