Diet-IPsec: Requirements for new IPsec/ESP protocols according to IoT use cases
draft-mglt-ipsecme-diet-esp-requirements-00.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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This Internet-Draft will expire on January 3, 2015.

Copyright Notice

Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved.

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Table of Contents

• 1. Requirements notation
• 2. Introduction
• 3. Terminology
• 4. Byte-Alignment
• 5. Crypto-Suites
• 6. Compression
• 7. Flexibility
• 8. Code Complexity
• 9. Usability
• 10. Compatibility with IP compression Protocols
• 11. Compatibility with Standard ESP
• 12. IANA Considerations
• 13. Security Considerations
• 14. Acknowledgment
• 15. Normative References
• Appendix A. Power Consumption Example
• Appendix B. Document Change Log
• Authors' Addresses

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:

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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.

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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.

-

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.

A common disadvantage of IPsec is that it is mostly implemented in the kernel, whereas application are in the user space. 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

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IoT: Internet of Things

4. 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 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.

R1:

Diet-ESP SHOULD support Byte-Alignment that are different from 32 bits or 64 bits to prevent unnecessary padding.

R2:

Each peer SHOULD be able to advertise and negotiate the Byte-Alignment, used for Diet-ESP. This could be done for example during the IKEv2 exchange.

5. 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.

R3:

Diet-ESP MUST support AES-CCM and MUST be able to take advantage of AES-CCM hardware acceleration. Diet-ESP MAY support other modes.

6. 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.

R4:

Diet-ESP SHOULD be able to compress/remove all static ESP fields (SPI, Next Header) as well as the other fields SN, PADDING, Pad Length or ICV.

R5:

Diet-ESP SHOULD also allow compression mechanisms before the IPsec/ESP processing.

R6:

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.

7. 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. In fact Diet-ESP and ESP differs in the following point: ESP has been designed so that any ESP secured communication on 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.

R7:

The developer SHOULD be able to specify the maximum level of compression.

R8:

Diet-ESP SHOULD be able to compress any field independent from another.

R9:

Diet-ESP SHOULD be able to define different compression method, when appropriated.

R10:

Each peer SHOULD be able to announce and negotiate the different compressed fields as well as the used method.

8. Code Complexity

IoT devices have limited space for memory and storage.

R11:

Diet-ESP SHOULD be able to be implemented with minimal complexity. More especially, Diet-ESP SHOULD consider small implementation that implement only a subset of all Diet-ESP capabilities without requiring involving standard ESP, specific compressors and de-compressors.

9. Usability

Application Developer usually do not want to take care about the underlying protocols and security. Standard ESP addresses the goal by providing a framework that secures communication in any circumstances. Although application developers for IoT are expected to pay more attention to the device security and system requirements, we do not expect them to be security aware developers. As a result, some default parameters that provides a standard secure framework for most cases should be provided. This is of course performed at the expense of some optimization, but it makes possible for application developers to have "standard" security and standard Diet-ESP compression by setting a single bit "DIET-ESP secure". More advanced developers will be able to tune the security parameters for their needs.

R12:

Diet-ESP SHOULD provide default configurations, which can be easily set up by a developer.

10. Compatibility with IP compression Protocols

There are different protocols providing IP layer compression for constraint devices like IoT (6LoWPAN [RFC6282] ) or Mobile Devices (ROHC).

R13:

Diet-ESP SHOULD be able to interact with IP compression protocols. More especially, this means that a Diet-ESP packet SHOULD be able to be sent in a ROHC or a 6LowPAN packet. Diet-ESP document should explicitly detail how this can be achieved.

R14:

Diet-ESP SHOULD also detail how compression of layers above IP with ROHC or 6LowPAN is compatible with Diet-ESP.

11. 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.

R15:

Diet-ESP SHOULD be able to interact with Standard ESP implementations on a single platform.

R16:

Diet-ESP SHOULD be able to communicate with Standard ESP.

12. IANA Considerations

There are no IANA consideration for this document.

13. Security Considerations

14. Acknowledgment

The current draft represents the work of Tobias Guggemos while his internship at Orange [GUGG14].

Diet-ESP is a joint work between Orange and Ludwig-Maximilians-Universitaet Munich. We thank Daniel Palomares and Carsten Bormann for their useful remarks, comments and guidance.

15. Normative References

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

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.