Internet DRAFT - draft-hartke-dice-profile
draft-hartke-dice-profile
dice K. Hartke
Internet-Draft Universitaet Bremen TZI
Intended status: Informational H. Tschofenig
Expires: August 18, 2014 ARM Ltd.
February 14, 2014
A DTLS 1.2 Profile for the Internet of Things
draft-hartke-dice-profile-03
Abstract
This document defines a DTLS profile that is suitable for Internet of
Things applications and is reasonably implementable on many
constrained devices.
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
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This Internet-Draft will expire on August 18, 2014.
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. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. The Communication Model . . . . . . . . . . . . . . . . . . . 4
3. The Ciphersuite Concept . . . . . . . . . . . . . . . . . . . 5
4. Pre-Shared Secret Authentication with DTLS . . . . . . . . . 6
5. Raw Public Key Use with DTLS . . . . . . . . . . . . . . . . 8
6. Certificate Use with DTLS . . . . . . . . . . . . . . . . . . 10
7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 11
8. Session Resumption . . . . . . . . . . . . . . . . . . . . . 12
9. TLS Compression . . . . . . . . . . . . . . . . . . . . . . . 13
10. Perfect Forward Secrecy . . . . . . . . . . . . . . . . . . . 13
11. Keep-Alive . . . . . . . . . . . . . . . . . . . . . . . . . 14
12. Negotiation and Downgrading Attacks . . . . . . . . . . . . . 14
13. Privacy Considerations . . . . . . . . . . . . . . . . . . . 14
14. Security Considerations . . . . . . . . . . . . . . . . . . . 15
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
16. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
17.1. Normative References . . . . . . . . . . . . . . . . . . 16
17.2. Informative References . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
This document defines a DTLS 1.2 [RFC6347] profile that offers
communication security for Internet of Things (IoT) applications and
is reasonably implementable on many constrained devices. It aims to
meet the following goals:
o One-stop shop for implementers through the specification jungle.
o This document does not alter the DTLS 1.2 specification.
o This document does not introduce new extensions.
o This profile aligns with the DTLS security modes of the
Constrained Application Protocol (CoAP) [I-D.ietf-core-coap].
DTLS is used to secure a number of applications run over an
unreliable datagram transport. CoAP [I-D.ietf-core-coap] is one such
protocol and has been designed specifically for use in IoT
environments. CoAP can be secured using a number of different ways,
also called security modes. These security modes are:
No Security Protection at the Transport Layer: No DTLS is used but
instead application layer security functionality is assumed.
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Shared Secret-based DTLS Authentication: DTLS supports the use of
shared secrets [RFC4279]. This credential is useful if the number
of communication relationships between the IoT device and servers
is small and for very constrained devices. Shared secret-based
authentication mechanisms offer good performance and require a
minimum of data to be exchanged.
DTLS Authentication using Asymmetric Credentials: TLS supports
client and server authentication using asymmetric credentials.
Two approaches for validating these public key are available.
First, [I-D.ietf-tls-oob-pubkey] allows raw public keys to be used
in TLS without the overhead of certificates. This approach
requires out-of-band validation of the public key. Second, the
use of X.509 certificates [RFC5280] with TLS is common on the Web
today (at least for server-side authentication) and certain IoT
environments may also re-use those capabilities. Certificates
bind an identifier to the public key signed by a certification
authority (CA). A trust anchor store has to be provisioned on the
device to indicate what CAs are trusted. Furthermore, the
certificate may contain a wealth of other information used to make
authorization decisions.
As described in [I-D.ietf-lwig-tls-minimal] an application designer
developing an IoT device needs to think about the security threats
that need to be mitigated. For many Internet connected devices it
is, however, likely that authentication of the device and the server
infrastructure will be required. Along with the ability to upload
sensor data and to retrieve configuration information the need for
integrity and confidentiality protection will arise. While these
security services can be provided at different layers in the protocol
stack the use of channel security, as offered by DTLS, has been very
popular on the Internet and it is likely to be useful for IoT
scenarios as well. In case the channel security features offered by
DTLS meet the security requirements of your application the remainder
of the document might offer useful guidance.
Not every IoT deployment will use CoAP but the discussion regarding
choice of credentials and cryptographic algorithms will be very
similar. As such, the discussions in this document are applicable
beyond the use of the CoAP protocol.
The design of DTLS is intentionally very similar to TLS. Since DTLS
operates on top of an unreliable datagram transport a few
enhancements to the TLS structure are, however necessary. RFC 6347
explains these differences in great detail. As a short summary, for
those familiar with TLS the differences are:
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o An explicit sequence number and an epoch field is included in the
TLS Record Layer. Section 4.1 of RFC 6347 explains the processing
rules for these two new fields. The value used to compute the MAC
is the 64-bit value formed by concatenating the epoch and the
sequence number.
o Stream ciphers must not be used with DTLS. The only stream cipher
defined for TLS 1.2 is RC4.
o The TLS Handshake Protocol has been enhanced to include a
stateless cookie exchange for Denial of Service (DoS) resistance.
Furthermore, the header has been extended to deal with message
loss, reordering, and fragmentation. Retransmission timers have
been included to deal with message loss. For DoS protection a new
handshake message, the HelloVerifyRequest, was added to DTLS.
This handshake message is sent by the server and includes a
stateless cookie, which is returned in a ClientHello message back
to the server. This type of DoS protection mechanism has also
been incorporated into the design of IKEv2. Although the exchange
is optional for the server to execute, a client implementation has
to be prepared to respond to it.
2. The Communication Model
This document describes a profile of DTLS 1.2 and to be useful it has
to make assumptions about the envisioned communication architecture.
The architecture shown in Figure 1 assumes a uni-cast communication
interaction with an IoT device acting as a client and the client
interacts with one or multiple servers. Which server to contact is
based on pre-configuration onto the client (e.g., as part of the
firmware). This configuration information also includes information
about the PSK identity and the corresponding secret to be used with
that specific server (in case of symmetric credentials). For
asymmetric cryptography mutual authentication is assumed in this
profile. For raw public keys the public key or the hash of the
public key is assumed to be available to both parties. For
certificate-based authentication the client may have a trust anchor
store pre-populated, which allows the client to perform path
validation for the certificate obtained during the handshake with the
server. The client also needs to know which certificate or raw
public key it has to use with a specific server.
This document only focuses on the description of the DTLS client-side
functionality.
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+////////////////////////////////////+
| Configuration |
|////////////////////////////////////|
| Server A --> PSK Identity, PSK |
| Server B --> Public Key (Server B),|
| Public Key (Client) |
| Server C --> Public Key (Client), |
| Trust Anchor Store |
+------------------------------------+
oo
oooooo
o
+------+
|Client|---
+------+ \
\ ,-------.
,' `. +------+
/ IP-based \ |Server|
( Network ) | A |
\ / +------+
`. ,'
'---+---' +------+
| |Server|
| | B |
| +------+
|
| +------+
+----------------->|Server|
| C |
+------+
Figure 1: DTLS Profile: Assumed Communication Model.
A future version of this document may provide profiles for other
communication architectures.
3. The Ciphersuite Concept
TLS (and consequently DTLS) introduced the concept of ciphersuites
and an IANA registry [IANA-TLS] was created to keep track of the
specified suites. A ciphersuites (and the specification that defines
it) contains the following information:
o Authentication and Key Exchange Algorithm (e.g., PSK)
o Cipher and Key Length(e.g., AES with 128 bit keys)
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o Mode of operation (e.g., CBC)
o Hash Algorithm for Integrity Protection (e.g., SHA in combination
with HMAC)
o Hash Algorithm for use with the Pseudorandom Function (e.g. HMAC
with the SHA-256)
o Misc information (e.g., length of authentication tags)
The TLS ciphersuite TLS_PSK_WITH_AES_256_CBC_SHA, for example, uses a
pre-shared authentication and key exchange algorithm. RFC 4279,
which defined this ciphersuite predates publication of TLS 1.2. It
uses the Advanced Encryption Standard (AES) encryption algorithm,
which is a block cipher. Since the AES algorithm supports different
key lengths (such as 128, 192 and 256 bits) this information has to
be specified as well and the selected ciphersuite supports 256 bit
keys. A block cipher encrypts plaintext in fixed-size blocks and AES
operates on fixed block size of 128 bits. For messages exceeding 128
bits, the message is partitioned into 128-bit blocks and the AES
cipher is applied to these input blocks with appropriate chaining,
which is called mode of operation. In our example, the mode of
operation is cipher block chaining (CBC). Since encryption itself
does not provide integrity protection a hash function is specified as
well, which will be used in concert with the HMAC function. In this
case, the Secure Hash Algorithm (SHA).
TLS 1.2 introduced Authenticated Encryption with Associated Data
(AEAD) ciphersuites. AEAD is a class of block cipher modes which
encrypt (parts of) the message and authenticate the message
simultaneously. Examples of such modes include the Counter with CBC-
MAC (CCM) mode, and the Galois/Counter Mode (GCM).
TLS 1.2 also replaced the combination of MD5/SHA-1 hash functions in
the TLS pseudo random function (PRF) with cipher-suite-specified
PRFs. For this reason authors of more recent TLS 1.2 ciphersuite
specifications explicitly indicate the MAC algorithm and the hash
functions used with the TLS PRF.
4. Pre-Shared Secret Authentication with DTLS
The use of pre-shared secret credentials is one of the most basic
techniques for DTLS since it is both computational efficient and
bandwidth conserving. Pre-shared secret based authentication was
introduced to TLS with RFC 4279 [RFC4279]. The exchange shown in
Figure 2 illustrates the DTLS exchange including the cookie exchange.
While the server is not required to initiate a cookie exchange with
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every handshake, the client is required to implement and to react on
it when challenged.
Client Server
------ ------
ClientHello -------->
<-------- HelloVerifyRequest
(contains cookie)
ClientHello -------->
(with cookie)
ServerHello
*ServerKeyExchange
<-------- ServerHelloDone
ClientKeyExchange
ChangeCipherSpec
Finished -------->
ChangeCipherSpec
<-------- Finished
Application Data <-------> Application Data
Legend:
* indicates an optional message payload
Figure 2: DTLS PSK Authentication including the Cookie Exchange.
[RFC4279] does not mandate the use of any particular type of
identity. Hence, the TLS client and server clearly have to agree on
the identities and keys to be used. The mandated encoding of
identities in Section 5.1 of RFC 4279 aims to improve
interoperability for those cases where the identity is configured by
a person using some management interface. Many IoT devices do,
however, not have a user interface and most of their credentials are
bound to the device rather than the user. Furthermore, credentials
are provisioned into trusted hardware modules or in the firmware by
the developers. As such, the encoding considerations are not
applicable to this usage environment. For use with this profile the
PSK identities MUST NOT assume a structured format (as domain names,
Distinguished Names, or IP addresses have) and a bit-by-bit
comparison operation can then be used by the server-side
infrastructure.
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As described in Section 2 clients may have pre-shared keys with
several different servers. The client indicates which key it uses by
including a "PSK identity" in the ClientKeyExchange message. To help
the client in selecting which PSK identity / PSK pair to use, the
server can provide a "PSK identity hint" in the ServerKeyExchange
message. For Iot environments a simplifying assumption is made that
the hint for PSK key selection is based on the domain name of the
server. Hence, servers SHOULD NOT send the "PSK identity hint" in
the ServerKeyExchange message and client MUST ignore the message.
RFC 4279 requires TLS implementations supporting PSK ciphersuites to
support arbitrary PSK identities up to 128 octets in length, and
arbitrary PSKs up to 64 octets in length. This is a useful
assumption for TLS stacks used in the desktop and mobile environment
where management interfaces are used to provision identities and
keys. For the IoT environment, however, many devices are not
equipped with displays and input devices (e.g., keyboards). Hence,
keys are distributed as part of hardware modules or are embedded into
the firmware. As such, these restrictions are not applicable to this
profile.
Constrained Application Protocol (CoAP) [I-D.ietf-core-coap]
currently specifies TLS_PSK_WITH_AES_128_CCM_8 as the mandatory to
implement ciphersuite for use with shared secrets. This ciphersuite
uses the AES algorithm with 128 bit keys and CCM as the mode of
operation. The label "_8" indicates that an 8-octet authentication
tag is used. This ciphersuite makes use of the default TLS 1.2
Pseudorandom Function (PRF), which uses HMAC with the SHA-256 hash
function.
5. Raw Public Key Use with DTLS
The use of raw public keys with DTLS, as defined in
[I-D.ietf-tls-oob-pubkey], is the first entry point into public key
cryptography without having to pay the price of certificates and a
PKI. The specification re-uses the existing Certificate message to
convey the raw public key encoded in the SubjectPublicKeyInfo
structure. To indicate support two new TLS extensions had been
defined as shown in Figure 3, namely the server_certificate_type and
the client_certificate_type. To operate this mechanism securely it
is necessary to authenticate and authorize the public keys out-of-
band. This document therefore assumes that a client implementation
comes with one or multiple raw public keys of servers, it has to
communicate with, pre-provisioned. Additionally, a device will have
its own raw public key. To replace, delete, or add raw public key to
this list requires a software update, for example using a firmware
update.
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Client Server
------ ------
ClientHello -------->
client_certificate_type
server_certificate_type
<------- HelloVerifyRequest
ClientHello -------->
client_certificate_type
server_certificate_type
ServerHello
client_certificate_type
server_certificate_type
Certificate
ServerKeyExchange
CertificateRequest
<-------- ServerHelloDone
Certificate
ClientKeyExchange
CertificateVerify
[ChangeCipherSpec]
Finished -------->
[ChangeCipherSpec]
<-------- Finished
Figure 3: DTLS Raw Public Key Exchange including the Cookie Exchange.
The ciphersuite for use with this credential type is
TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 [I-D.mcgrew-tls-aes-ccm-ecc].
This elliptic curve cryptography (ECC) based AES-CCM TLS ciphersuite
uses the Elliptic Curve Diffie Hellman (ECDHE) as the key
establishment mechanism and an Elliptic Curve Digital Signature
Algorithm (ECDSA) for authentication. This ciphersuite make use of
the AEAD capability in DTLS 1.2 and utilizes an eight-octet
authentication tag. Based on the Diffie-Hellman it provides perfect
forward secrecy (PFS). More details about the PFS can be found in
Section 10.
RFC 6090 [RFC6090] provides valuable information for implementing
Elliptic Curve Cryptography algorithms.
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Since many IoT devices will either have limited ways to log error or
no ability at all, any error will lead to implementations attempting
to re-try the exchange.
QUESTION: [I-D.sheffer-tls-bcp] recommends a different ciphersuite,
namely TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 [RFC5289] or
alternatively TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (with a 2048-bit or
1024 DH parameters as second and third priority, respectively). Is
TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 a good choice?
6. Certificate Use with DTLS
The use of mutual certificate-based authentication is shown in
Figure 4. Note that the figure also makes use of the cached info
extension, which is indicated by the TLS extension
(cached_information) and the changed content in the exchanged
certificates. Caching certificate chains allows the client to reduce
the communication overhead significantly since otherwise the server
would provide the end entity certificate, and the certificate chain.
Because certificate validation requires that root keys be distributed
independently, the self-signed certificate that specifies the root
certificate authority is omitted from the chain. Client
implementations MUST be provisioned with a trust anchor store that
contains the root certificates. The use of the Trust Anchor
Management Protocol (TAMP) [RFC5934] is, however, not envisioned.
Instead IoT devices using this profile MUST rely a software update
mechanism to provision these trust anchors.
When DTLS is used to secure CoAP messages then the server provided
certificates MUST contain the fully qualified DNS domain name or
"FQDN". The coaps URI scheme is described in Section 6.2 of
[I-D.ietf-core-coap]. This FQDN is stored in the SubjectAltName or
in the CN, as explained in Section 9.1.3.3 of [I-D.ietf-core-coap],
and used by the client to match it against the FQDN used during the
look-up process, as described in RFC 6125 [RFC6125]. For the profile
in this specification does not assume dynamic discovery of local
servers.
For client certificates the identifier used in the SubjectAltName or
in the CN MUST be an EUI-64 [EUI64], as mandated in Section 9.1.3.3
of [I-D.ietf-core-coap].
For certificate revocation neither the Online Certificate Status
Protocol (OCSP) nor Certificate Revocation Lists (CRLs) are used.
Instead, this profile relies on a software update mechanism. While
multiple OCSP stapling [RFC6961] has recently been introduced as a
mechanism to piggyback OCSP request/responses inside the DTLS/TLS
handshake to avoid the cost of a separate protocol handshake further
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investigations are needed to determine its suitability for the IoT
environment.
Client Server
------ ------
ClientHello -------->
cached_information
<------- HelloVerifyRequest
ClientHello -------->
cached_information
ServerHello
cached_information
Certificate
ServerKeyExchange
CertificateRequest
<-------- ServerHelloDone
Certificate
ClientKeyExchange
CertificateVerify
[ChangeCipherSpec]
Finished -------->
[ChangeCipherSpec]
<-------- Finished
Figure 4: DTLS Mutual Certificate-based Authentication.
Regarding the ciphersuite choice the discussion in Section 5 applies.
Further details about X.509 certificates can be found in
Section 9.1.3.3 of [I-D.ietf-core-coap].
QUESTION: What restrictions regarding the depth of the certificate
chain should be made? Is one level enough?
7. Error Handling
DTLS uses the Alert protocol to convey error messages and specifies a
longer list of errors. However, not all error messages defined in
the TLS specification are applicable to this profile. All error
messages marked as RESERVED are only supported for backwards
compatibility with SSL and are therefore not applicable to this
profile. Those include decryption_failed_RESERVED,
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no_certificate_RESERVE, and export_restriction_RESERVED. A number of
the error messages are applicable only for certificate-based
authentication ciphersuites. Hence, for PSK and raw public key use
the following error messages are not applicable: bad_certificate,
unsupported_certificate, certificate_revoked, certificate_expired,
certificate_unknown, unknown_ca, and access_denied.
Since this profile does not make use of compression at the TLS layer
the decompression_failure error message is not applicable either.
RFC 4279 introduced a new alert message unknown_psk_identity for PSK
ciphersuites. As stated in Section 2 of RFC 4279 the
decryption_error error message may also be used instead. For this
profile the TLS server MUST return the decryption_error error message
instead of the unknown_psk_identity.
Furthermore, the following errors should not occur based on the
description in this specification:
protocol_version: This document only focuses on one version of the
DTLS protocol.
insufficient_security: This error message indicates that the server
requires ciphers to be more secure. This document does, however,
specify the only acceptable ciphersuites and client
implementations must support them.
user_canceled: The IoT devices in focus of this specification are
assumed to be unattended.
8. Session Resumption
Session resumption is a feature of DTLS that allows a client to
continue with an earlier established session state. The resulting
exchange is shown in Figure 5. In addition, the server may choose
not to do a cookie exchange when a session is resumed. Still,
clients have to be prepared to do a cookie exchange with every
handshake.
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Client Server
------ ------
ClientHello -------->
ServerHello
[ChangeCipherSpec]
<-------- Finished
[ChangeCipherSpec]
Finished -------->
Application Data <-------> Application Data
Figure 5: DTLS Session Resumption.
Clients MUST implement session resumption to improve the performance
of the handshake (in terms of reduced number of message exchanges,
lower computational overhead, and less bandwidth conserved).
Since the communication model described in Section 2 does not assume
that the server is constrained. RFC 5077 [RFC5077] describing TLS
session resumption without server-side state is not utilized by this
profile.
9. TLS Compression
[I-D.sheffer-tls-bcp] recommends to always disable DTLS-level
compression due to attacks. For IoT applications compression at the
DTLS is not needed since application layer protocols are highly
optimized and the compression algorithms at the DTLS layer increase
code size and complexity. Hence, for use with this profile
compression at the DTLS layer MUST NOT be implemented by the DTLS
client.
10. Perfect Forward Secrecy
Perfect forward secrecy is designed to prevent the compromise of a
long-term secret key from affecting the confidentiality of past
conversations. The PSK ciphersuite recommended in the CoAP
specification [I-D.ietf-core-coap] does not offer this property.
[I-D.sheffer-tls-bcp] on the other hand recommends using ciphersuites
offering this security property.
QUESTION: Should the PSK ciphersuite offer PFS?
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11. Keep-Alive
RFC 6520 [RFC6520] defines a heartbeat mechanism to test whether the
other peer is still alive. The same mechanism can also be used to
perform path MTU discovery.
QUESTION: Do IoT deployments make use of this extension?
12. Negotiation and Downgrading Attacks
CoAP demands version 1.2 of DTLS to be used and the earlier version
of DTLS is not supported. As such, there is no risk of downgrading
to an older version of DTLS. The work described in
[I-D.bmoeller-tls-downgrade-scsv] is therefore also not applicable to
this environment since there is no legacy server infrastructure to
worry about.
QUESTION: Should we say something for non-CoAP use of DTLS?
To prevent the TLS renegotiation attack [RFC5746] clients MUST
respond to server-initiated renegotiation attempts with an Alert
message (no_renegotiation) and clients MUST NOT initiate them. TLS
and DTLS allows a client and a server who already have a TLS
connection to negotiate new parameters, generate new keys, etc by
initiating a TLS handshake using a ClientHello message.
Renegotiation happens in the existing TLS connection, with the new
handshake packets being encrypted along with application data.
13. Privacy Considerations
The DTLS handshake exchange conveys various identifiers, which can be
observed by an on-path eavesdropper. For example, the DTLS PSK
exchange reveals the PSK identity, the supported extensions, the
session id, algorithm parameters, etc. When session resumption is
used then individual TLS sessions can be correlated by an on-path
adversary. With many IoT deployments it is likely that keying
material and their identifiers are persistent over a longer period of
time due to the cost of updating software on these devices.
User participation with many IoT deployments poses a challenge since
many of the IoT devices operate unattended, even though they will
initially be enabled by a human. The ability to control data sharing
and to configure preference will have to be provided at a system
level rather than at the level of a DTLS profile, which is the scope
of this document. Quite naturally, the use of DTLS with mutual
authentication will allow a TLS server to collect authentication
information about the IoT device (potentially over a long period of
time). While this strong form of authentication will prevent mis-
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attribution it also allows strong identification. This device-
related data collection (e.g., sensor recordings) will be associated
with other data to be truly useful and this extra data might include
personal data about the owner of the device or data about the
environment it senses. Consequently, the data stored on the server-
side will be vulnerable to stored data compromise. For the
communication between the client and the server this specification
prevents eavesdroppers to gain access to the communication content.
While the PSK-based ciphersuite does not provide PFS the asymmetric
version does. No explicit techniques, such as extra padding, have
been provided to make traffic analysis more difficult.
14. Security Considerations
This entire document is about security.
The TLS protocol requires random numbers to be available during the
protocol run. For example, during the ClientHello and the
ServerHello exchange the client and the server exchange random
numbers. Also, the use of the Diffie Hellman exchange requires
random numbers during the key pair generation. Special care has to
be paid when generating random numbers in embedded systems as many
entropy sources available on desktop operating systems or mobile
devices might be missing, as described in [Heninger]. Consequently,
if not enough time is given during system start time to fill the
entropy pool then the output might be predictable and repeatable, for
example leading to the same keys generated again and again.
Guidelines and requirements for random number generation can be found
in RFC 4086 [RFC4086].
We would also like to point out that designing a software update
mechanism into an IoT system is crucial to ensure that both
functionality can be enhanced and that potential vulnerabilities can
be fixed. This software update mechanism is also useful for changing
configuration information, for example, trust anchors and other
keying related information.
15. IANA Considerations
This document includes no request to IANA.
16. Acknowledgements
Thanks to Rene Hummen, Sye Loong Keoh, Sandeep Kumar, Eric Rescorla,
Zach Shelby, and Sean Turner for helpful comments and discussions
that have shaped the document.
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17. References
17.1. Normative References
[EUI64] "GUIDELINES FOR 64-BIT GLOBAL IDENTIFIER (EUI-64)
REGISTRATION AUTHORITY", April 2010,
<http://standards.ieee.org/regauth/oui/tutorials/
EUI64.html>.
[I-D.ietf-core-coap]
Shelby, Z., Hartke, K., and C. Bormann, "Constrained
Application Protocol (CoAP)", draft-ietf-core-coap-18
(work in progress), June 2013.
[I-D.ietf-tls-cached-info]
Santesson, S. and H. Tschofenig, "Transport Layer Security
(TLS) Cached Information Extension", draft-ietf-tls-
cached-info-15 (work in progress), October 2013.
[I-D.ietf-tls-oob-pubkey]
Wouters, P., Tschofenig, H., Gilmore, J., Weiler, S., and
T. Kivinen, "Using Raw Public Keys in Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", draft-ietf-tls-oob-pubkey-11 (work in progress),
January 2014.
[I-D.mcgrew-tls-aes-ccm-ecc]
McGrew, D., Bailey, D., Campagna, M., and R. Dugal, "AES-
CCM ECC Cipher Suites for TLS", draft-mcgrew-tls-aes-ccm-
ecc-08 (work in progress), February 2014.
[RFC4279] Eronen, P. and H. Tschofenig, "Pre-Shared Key Ciphersuites
for Transport Layer Security (TLS)", RFC 4279, December
2005.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5746] Rescorla, E., Ray, M., Dispensa, S., and N. Oskov,
"Transport Layer Security (TLS) Renegotiation Indication
Extension", RFC 5746, February 2010.
[RFC6066] Eastlake, D., "Transport Layer Security (TLS) Extensions:
Extension Definitions", RFC 6066, January 2011.
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[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, March 2011.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012.
[RFC6520] Seggelmann, R., Tuexen, M., and M. Williams, "Transport
Layer Security (TLS) and Datagram Transport Layer Security
(DTLS) Heartbeat Extension", RFC 6520, February 2012.
17.2. Informative References
[Heninger]
Heninger, N., Durumeric, Z., Wustrow, E., and A.
Halderman, "Mining Your Ps and Qs: Detection of Widespread
Weak Keys in Network Devices", 21st USENIX Security
Symposium, https://www.usenix.org/conference/
usenixsecurity12/technical-sessions/presentation/heninger,
2012.
[I-D.bmoeller-tls-downgrade-scsv]
Moeller, B. and A. Langley, "TLS Fallback Signaling Cipher
Suite Value (SCSV) for Preventing Protocol Downgrade
Attacks", draft-bmoeller-tls-downgrade-scsv-01 (work in
progress), November 2013.
[I-D.campagna-suitee]
Campagna, M., "A Cryptographic Suite for Embedded Systems
(SuiteE)", draft-campagna-suitee-04 (work in progress),
October 2012.
[I-D.cooper-ietf-privacy-requirements]
Cooper, A., Farrell, S., and S. Turner, "Privacy
Requirements for IETF Protocols", draft-cooper-ietf-
privacy-requirements-01 (work in progress), October 2013.
[I-D.greevenbosch-tls-ocsp-lite]
Greevenbosch, B., "OCSP-lite - Revocation of raw public
keys", draft-greevenbosch-tls-ocsp-lite-01 (work in
progress), June 2013.
[I-D.gutmann-tls-encrypt-then-mac]
Gutmann, P., "Encrypt-then-MAC for TLS and DTLS", draft-
gutmann-tls-encrypt-then-mac-05 (work in progress),
December 2013.
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[I-D.hummen-dtls-extended-session-resumption]
Hummen, R., Gilger, J., and H. Shafagh, "Extended DTLS
Session Resumption for Constrained Network Environments",
draft-hummen-dtls-extended-session-resumption-01 (work in
progress), October 2013.
[I-D.ietf-lwig-guidance]
Bormann, C., "Guidance for Light-Weight Implementations of
the Internet Protocol Suite", draft-ietf-lwig-guidance-03
(work in progress), February 2013.
[I-D.ietf-lwig-terminology]
Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained Node Networks", draft-ietf-lwig-terminology-06
(work in progress), December 2013.
[I-D.ietf-lwig-tls-minimal]
Kumar, S., Keoh, S., and H. Tschofenig, "A Hitchhiker's
Guide to the (Datagram) Transport Layer Security Protocol
for Smart Objects and Constrained Node Networks", draft-
ietf-lwig-tls-minimal-00 (work in progress), September
2013.
[I-D.ietf-tls-applayerprotoneg]
Friedl, S., Popov, A., Langley, A., and S. Emile,
"Transport Layer Security (TLS) Application Layer Protocol
Negotiation Extension", draft-ietf-tls-applayerprotoneg-04
(work in progress), January 2014.
[I-D.pettersen-tls-version-rollback-removal]
Pettersen, Y., "Managing and removing automatic version
rollback in TLS Clients", draft-pettersen-tls-version-
rollback-removal-02 (work in progress), August 2013.
[I-D.sheffer-tls-bcp]
Sheffer, Y. and R. Holz, "Recommendations for Secure Use
of TLS and DTLS", draft-sheffer-tls-bcp-01 (work in
progress), September 2013.
[IANA-TLS]
IANA, "TLS Cipher Suite Registry", http://www.iana.org/
assignments/tls-parameters/
tls-parameters.xhtml#tls-parameters-4, 2014.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552, July
2003.
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[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
Requirements for Security", BCP 106, RFC 4086, June 2005.
[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
for Transport Layer Security (TLS)", RFC 4492, May 2006.
[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
"Transport Layer Security (TLS) Session Resumption without
Server-Side State", RFC 5077, January 2008.
[RFC5289] Rescorla, E., "TLS Elliptic Curve Cipher Suites with
SHA-256/384 and AES Galois Counter Mode (GCM)", RFC 5289,
August 2008.
[RFC5934] Housley, R., Ashmore, S., and C. Wallace, "Trust Anchor
Management Protocol (TAMP)", RFC 5934, August 2010.
[RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
Curve Cryptography Algorithms", RFC 6090, February 2011.
[RFC6961] Pettersen, Y., "The Transport Layer Security (TLS)
Multiple Certificate Status Request Extension", RFC 6961,
June 2013.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973, July
2013.
Authors' Addresses
Klaus Hartke
Universitaet Bremen TZI
Postfach 330440
Bremen D-28359
Germany
Phone: +49-421-218-63905
Email: hartke@tzi.org
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Hannes Tschofenig
ARM Ltd.
110 Fulbourn Rd
Cambridge CB1 9NJ
Great Britain
Email: Hannes.tschofenig@gmx.net
URI: http://www.tschofenig.priv.at
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