Internet DRAFT - draft-tschofenig-lwig-tls-minimal
draft-tschofenig-lwig-tls-minimal
Network Working Group H. Tschofenig
Internet-Draft Nokia Siemens Networks
Intended status: Standards Track S.S. Kumar
Expires: January 6, 2014 S. Keoh
Philips Research
July 5, 2013
A Hitchhiker's Guide to the (Datagram) Transport Layer Security Protocol
for Smart Objects and Constrained Node Networks
draft-tschofenig-lwig-tls-minimal-03
Abstract
Transport Layer Security (TLS) is a widely used security protocol
that offers communication security services at the transport layer.
The initial design of TLS was focused on the protection of
applications running on top of the Transmission Control Protocol
(TCP), and was a good match for securing the Hypertext Transfer
Protocol (HTTP). Subsequent standardization efforts lead to the
publication of the Datagram Transport Layer Security (DTLS) protocol,
which allows the re-use of the TLS security functionality and the
payloads to be exchanged on top of the User Datagram Protocol (UDP).
With the work on the Constrained Application Protocol (CoAP), as a
specialized web transfer protocol for use with constrained nodes and
constrained networks, DTLS is a preferred communication security
protocol.
Smart objects are constrained in various ways (e.g., CPU, memory,
power consumption) and these limitations may impose restrictions on
the protocol stack such a device runs. This document only looks at
the security part of that protocol stacks and the ability to
customize TLS/DTLS. To offer input for implementers and system
architects this document illustrates the costs and benefits of
various TLS/DTLS features for use with smart objects and constraint
node networks.
Requirements Language
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 RFC 2119 [RFC2119]
Status of this Memo
This Internet-Draft is submitted in full conformance with the
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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 August 29, 2013.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Design Decisions . . . . . . . . . . . . . . . . . . . . . . . 6
4. Performance Numbers . . . . . . . . . . . . . . . . . . . . . 7
4.1. Pre-Shared Key (PSK) based DTLS implementation . . . . . . 7
4.1.1. Prototype Environment . . . . . . . . . . . . . . . . . 7
4.1.2. Code size and Memory Consumption . . . . . . . . . . . 8
4.1.3. Communication Overhead . . . . . . . . . . . . . . . . 8
4.1.4. Message Delay, Success Rate and Bandwidth . . . . . . . 9
4.2. Certificate based and Raw-public key based TLS
implementation . . . . . . . . . . . . . . . . . . . . . . 10
4.3.1. Prototype Environment . . . . . . . . . . . . . . . . . 10
4.3.2. Code size . . . . . . . . . . . . . . . . . . . . . . . 10
4.3.2. Raw Public Key Implementation . . . . . . . . . . . . . 11
5. Summary and Conclusions . . . . . . . . . . . . . . . . . . . 12
6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
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8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.1. Normative References . . . . . . . . . . . . . . . . . . . 13
9.2. Informative References . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
The IETF published three versions of Transport Layer Security: TLS
Version 1.0 [RFC2246], TLS Version 1.1 [RFC4346], and TLS Version 1.2
[RFC5246]. Section 1.1 of [RFC4346] explains the differences between
Version 1.0 and Version 1.1; those are small security improvements,
including the usage of an explicit initialization vector to protect
against cipher-block-chaining attacks, which all have little to no
impact on smart object implementations. Section 1.2 of [RFC5246]
describes the differences between Version 1.1 and Version 1.2. TLS
1.2 introduces a couple of major changes with impact to size of an
implementation. In particular, prior TLS versions hard-coded the
MD5/SHA-1 combination in the pseudo-random function (PRF). As a
consequence, any TLS Version 1.0 and Version 1.1 implementation had
to have MD5 and SHA-1 code even if the remaining cryptographic
primitives used other algorithms. With TLS Version 1.2 the two had
been replaced with cipher-suite-specified PRFs. In addition, the TLS
extensions definition [RFC6066] and various AES ciphersuites
[RFC3268] got merged into the TLS Version 1.2 specification.
All three TLS specifications list a mandatory-to-implement
ciphersuite: for TLS Version 1.0 this was
TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA, for TLS Version 1.1 it was
TLS_RSA_WITH_3DES_EDE_CBC_SHA, and for TLS Version 1.2 it is
TLS_RSA_WITH_AES_128_CBC_SHA. There is, however, an important
qualification to these compliance statements, namely that they are
only valid in the absence of an application profile standard
specifying otherwise. The smart object environment may, for example,
represent a situation for such an application profile which defines a
cryptosuite that reduces memory and computation requirements without
sacrificing security.
All TLS versions offer a separation between authentication and key
exchange, and bulk data protection. The former is more costly
performance- and message-wise. The details of the authentication and
key exchange, using the TLS Handshake, vary with the chosen
ciphersuite. With new ciphersuites the TLS feature-set can easily be
enhanced, in case the already large collection of ciphersuites, see
[TLS-IANA], does not match the requirements.
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Once the TLS Handshake has been successfully completed the necessary
keying material and parameters are setup for usage with the TLS
Record Layer, which is responsible for bulk data protection. The
provided security of the TLS Record Layer depends also, but not only,
on the chosen ciphersuite algorithms; NULL encryption ciphersuites,
like those specified in RFC 4785 [RFC4785], offer only integrity-
without confidentiality-protection. Example ciphersuites for the TLS
Record Layer are RC4 with SHA-1, AES-128 with SHA-1, AES-256 with
SHA-1, RC4 with SHA-1, RC4 with MD5 It is worth mentioning that TLS
may also be used without the TLS Record Layer. This has, for example,
been exercised with the work on the framework for establishing a
Secure Real-time Transport Protocol (SRTP) security context using the
Datagram Transport Layer Security (DTLS [RFC4347]) protocol (DTLS-
SRTP [RFC5763]).
It is fair to say that TLS and consequently DTLS offers a fair degree
of flexibility. What specific security features of TLS are required
for a specific smart object application scenario depends on various
factors, including the communication architecture and the threats
that shall be mitigated.
The goal of this document is to provide guidance on how to use
existing DTLS/TLS extensions for smart objects and to explain their
costs in terms of code size, computational effort, communication
overhead, and (maybe) energy consumption. The document does not try
to be exhaustive, as the list of TLS/DTLS extensions is enhanced on a
frequent basis. Instead we focus on extensions that those working in
the smart object community often found valuable in their practical
experience. A non-goal is to propose new extensions to DTLS/TLS to
provide even better performance characteristics in specific
environments.
2. Overview
A security solution to be deployed is strongly influenced by the
communication relationships [RFC4101] between the entities. Having a
good understanding of these relationships will be essential to define
the threats and decide on how to customize the security solution.
Some of these considerations are described in [I-D.gilger-smart-
object-security-workshop].
Consider the following scenario where a smart-meter transmits its
energy readings to other parties. The public utility has to ensure
that the meter readings it obtained can be attributed to a specific
meter in a household. It is simply not acceptable for public utility
to have any meter readings tampered in transit or by a rogue endpoint
(particularly if the attack leads to a disadvantage, for example
financial loss, for the utility). Users in a household may want to
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ensure that only certain authorized parties are able to read their
meter; privacy concerns come to mind.
In this example, a smart-meter may only ever need to talk to servers
of a specific utility or even only to a single pre-configured server.
Clearly, some information has to be pre-provisioned into the device
to ensure the desired behavior to talk only to selected servers. The
meter may come pre-configured with the domain name and certificate
belonging to the utility. The device may, however, also be
configured to accept one or multiple server certificates. It may
even be pre-provisioned with the server's raw public key, or a shared
secret instead of relying on certificates.
Lowering the flexibility decreases the implementation overhead. If
shared secrets are used with TLS-PSK [RFC4279] or raw public keys are
used with TLS [I-D.ietf-tls-oob-pubkey], fewer lines of code are
needed than employing X.509 certificate, as will be explained later
in this document. A decision for constraining the client-side TLS
implementation, for example by offering only a single ciphersuite,
has to be made in awareness of what functionality will be available
on the TLS server-side. In certain communication environments it may
be easy to influence both communication partners while in other cases
the existing deployment needs to be taken into consideration.
To illustrate another example, consider an Internet radio, which
allows a user to connect to available radio stations. A device like
this will be more demanding than an IP-enabled weighing scale that
only connects to the single web server offered by the device
manufacturer. A threat assessment may even lead to the conclusion
that TLS support is not necessary at all in this particular case.
Consider the following extension to our earlier scenario where the
smart-meter is attached to a home WLAN network and the inter-working
with WLAN security mechanisms need to be taken care of. On top of
the link layer authentication, a transport layer or application layer
security mechanism needs to be implemented. Quite likely the
security mechanisms will be different due to the different credential
requirements. While there is a possibility for re-use of
cryptographic libraries (such as the SHA-1, MD5, or HMAC) the overall
code footprint will very likely be larger.
Furthermore, security technology that will be deployed by end-user
consumer market products and large enterprise customer products will
need to be customized completely different. While the security
building blocks may be reused, there is certainly a big difference
between in terms of the architecture, the threats and effort that
will be spent securing the system.
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3. Design Decisions
To evaluate the required TLS functionality a couple of high level
design decisions have to be made:
o What type of protection for the data traffic is required? Is
confidentiality protection in addition to integrity protection
required? Many TLS ciphersuites also provide a variant for NULL
encryption [RFC4279]. If confidentiality protection is required,
a carefully chosen set of algorithms may have a positive impact on
the code size. Re-use of crypto-libraries (within TLS but also
among the entire protocol stack) will also help to reduce the
overall code size.
o What functionality is available in hardware? For example, certain
hardware platforms offer support for a random number generator as
well as cryptographic algorithms (e.g., AES). These functions can
be re-used and allow to reduce the amount of required code. Using
hardware support not only reduces the computation time but can
also save energy due to the optimized implementation.
o What credentials for client and server authentication are
required: passwords, pre-shared secrets, certificates, raw public
keys (or a mixture of them)? Is mutual authentication required? Is
X509 certificate handling necessary? If not, then the ASN.1
library as well as the certificate parsing and processing can be
omitted. If pre-shared secrets are used then the big integer
implementation can be omitted.
o What TLS version and what TLS features, such as session
resumption, can or have to be used? In the case of DTLS, generic
fragmentation and reordering requires large buffers to reassemble
the messages, which might be too heavy for some devices.
o Is it possible to design only the client-side TLS stack, or
necessary to provide the server-side implementation as well?
Handshake messages sent are different sizes for the client and
server which creates energy consumption differences (due to the
fact that more power is spent during transmission than while
receiving data in wireless devices).
o Which side will be more powerful? Resource-constrained sensor
nodes running CoAPS might be server only, while nodes running
HTTPS are most like clients only that post their information to a
normal Web server. The constrained side will most likely only
implement a single ciphersuite. Flexibility is given to a more
powerful counterpart that supports many different ciphersuite for
various connected devices.
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o Is it possible to hardwire credentials into the code rather than
loading them from storage? If so, then no file handling or
parsing of the credentials is needed and the credentials are
already available in a form that they can be used within the TLS
implementation.
4. Performance Numbers
In this section we summarize performance measurements available from
certain implementation experiences. This section is not supposed to
be exhaustive as we do not have all measurements available. The
performances are grouped according to extensions (TLS-PSK, raw-public
key and certificate based) and further grouped by performance
measures (memory, code size, communication overhead, etc.). Where
possible we extract the different building blocks found in TLS and
present their performance measures individually.
4.1. Pre-Shared Key (PSK) based DTLS implementation
This section provides performance numbers for a prototype
implementation of DTLS-PSK described in [I-D.keoh-lwig-dtls-iot] and
evaluates the memory and communication overheads.
4.1.1. Prototype Environment
The prototype is written in C and runs as an application on Contiki
OS 2.5 [Dunkels-contiki], an event-driven open source operating
system for constrained devices. They were tested in the Cooja
simulator and then ported to run on Redbee Econotag hardware, which
features a 32-bit CPU, 128 KB of ROM, 128 KB of RAM, and an IEEE
802.15.4 enabled radio with an AES hardware coprocessor. The
prototype comprises all necessary functionality to adapt to the roles
as a domain manager or a joining device.
The prototype is based on the "TinyDTLS" [Bergmann-Tinydtls] library
and includes most of the extensions and the adaptation as follows:
(1) The cookie mechanism was disabled in order to fit messages to the
available packet sizes and hence reducing the total number of
messages when performing the DTLS handshake.
(2) Separate delivery was used instead of flight grouping of messages
and redesigned the retransmission mechanism accordingly.
(3) The "TinyDTLS" AES-CCM module was modified to use the AES
hardware coprocessor.
The following subsections further analyze the memory and
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communication overhead of the solution.
4.1.2. Code size and Memory Consumption
Table 1 presents the codesize and memory consumption of the prototype
differentiating (i) the state machine for the handshake, (ii) the
cryptographic primitives, and (iii) the DTLS record layer mechanism.
The use of DTLS appears to incur large memory footprint both in ROM
and RAM for two reasons. First, DTLS handshake defines many message
types and this adds more complexity to its corresponding state
machine. The logic for message re-ordering and retransmission also
contributes to the complexity of the DTLS state machine. Second, DTLS
uses SHA2-based crypto suites which is not available from the
hardware crypto co-processor.
+----------------------+-----------------+
| | DTLS |
| +--------+--------+
| | ROM | RAM |
+----------------------+--------+--------+
| State Machine | 8.15 | 1.9 |
| Cryptography | 3.3 | 1.5 |
| Key Management | 1.0 | 0.0 |
| DTLS Record Layer | 3.7 | 0.5 |
+----------------------+--------+--------+
| TOTAL | 16.15 | 3.9 |
+----------------------+--------+--------+
Table 1: Memory Requirements in KB
4.1.3. Communication Overhead
The communication overhead is evaluated in this section. In
particular, the message overhead and the number of exchanged bytes
under ideal condition without any packet loss is examined.
Table 2 summarizes the required number of round trips, number of
messages and the total exchanged bytes for the DTLS-based handshake
carried out in ideal conditions, i.e., in a network without packet
losses. DTLS handshake is considered complex as it involves the
exchange of 12 messages to complete the handshake. Further, DTLS runs
on top the transport layer, i.e., UDP, and hence this directly
increases the overhead due to lower layer per-packet protocol
headers.
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+-------------------------------+--------+
| | DTLS |
+-------------------------------+--------+
| No. of Message | 12 |
| No. of round trips | 4 |
+-------------------------------+--------+
| 802.15.4 headers | 168B |
| 6LowPAN headers | 480B |
| UDP headers | 96B |
| Application | 487B |
+-------------------------------+--------+
| TOTAL | 1231B |
+-------------------------------+--------+
Table 2: Communication overhead for Network
Access and Multicast Key Management
4.1.4. Message Delay, Success Rate and Bandwidth
Section 5.3 provided an evaluation of the protocol in an ideal
condition, thus establishing the the baseline protocol overhead. The
prototype was further examined and simulated the protocol behavior by
tuning the packet loss ratio. In particular, the impact of packet
loss on message delay, success rate and number of messages exchanged
in the handshake were examined.
Figure 4 shows the percentage of successful handshakes as a function
of timeouts and packet loss ratios. As expected, a higher packet loss
ratio and smaller timeout (15s timeout) result in a failure
probability of completing the DTLS handshake. When the packet loss
ratio reaches 0.5, practically no DTLS handshake would be
successful.
100 |+
P | +
E 80 | ++
R | ++
C 60 | +
E | +
N 40 | +
T | ++
A 20 | +
G | +++++
E 0 +------------------++++++++-->
0 0.1 0.2 0.3 0.4 0.5
packet loss ratio (15s timeout)
Figure 1: Average % of successful handshakes
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Delays in network access and communication are intolerable since they
lead to higher resource consumption. As the solution relies on PSK,
the handshake protocol only incurs a short delay of a few
milliseconds when there is no packet loss. However, as the packet
loss ratio increases, the delay in completing the handshake becomes
significant because loss packets must be retransmitted. Our
implementation shows that with a packet loss ratio of 0.5, the the
times to perform network access and multicast key management could
take up to 24s.
Finally, another important criterion is the number of messages
exchanged in the presence of packet loss. A successful handshake
could incur up to 35 or more messages to be transmitted when the
packet loss ratio reaches 0.5. This is mainly because the DTLS
retransmission is complex and often requires re-sending multiple
messages even when only a single message has been lost.
4.2. Certificate based and Raw-public key based TLS implementation
4.3.1. Prototype Environment
The following code was compiled under Ubuntu Linux using the -Os
compiler flag setting for a 64-bit AMD machine using a modified
version of the axTLS embedded SSL implementation.
4.3.2. Code size
For the cryptographic support functions these are the binary sizes:
+----------------------------+---------------+
| Cryptographic functions | Code size |
+----------------------------+---------------+
| MD5 | 4,856 bytes |
| SHA1 | 2,432 bytes |
| HMAC | 2,928 bytes |
| RSA | 3,984 bytes |
| Big Integer Implementation | 8,328 bytes |
| AES | 7,096 bytes |
| RC4 | 1,496 bytes |
| Random Number Generator | 4,840 bytes |
+----------------------------+---------------+
Table 3: Code-size for cryptographic functions
The TLS library with certificate support consists of the following
parts:
x509 related code: 2,776 bytes
The x509 related code provides functions to parse certificates, to
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copy them into the program internal data structures and to perform
certificate related processing functions, like certificate
verification.
ASN1 Parser: 5,512 bytes
The ASN1 library contains the necessary code to parse ASN1 data.
Generic TLS Library: 15,928 bytes
This library is separated from the TLS client specific code to offer
those functions that are common with the client and the server-side
implementation. This includes code for the master secret generation,
certificate validation and identity verification, computing the
finished message, ciphersuite related functions, encrypting and
decrypting data, sending and receiving TLS messages (e.g., finish
message, alert messages, certificate message, session resumption).
TLS Client Library: 4,584 bytes
The TLS client-specific code includes functions that are only
executed by the client based on the supported ciphersuites, such as
establishing the connection with the TLS server, sending the
ClientHello handshake message, parsing the ServerHello handshake
message, processing the ServerHelloDone message, sending the
ClientKeyExchange message, processing the CertificateRequest message.
OS Wrapper Functions: 2,776 bytes
These functions aim to make development easier (e.g., for failure
handling with memory allocation and various header definitions) but
are not absolutely necessary.
OpenSSL Wrapper Functions: 931 bytes
The OpenSSL API calls are familiar to many programmers and therefore
these wrapper functions are provided to simplify application
development. This library is also not absolutely necessary.
Certificate Processing Functions: 4,456 bytes
These functions provide the ability to load certificates from files
(or to use a default key as a static data structure embedded during
compile time), to parse them, and populate corresponding data
structures.
4.3.2. Raw Public Key Implementation
Of course, the use of raw public keys does not only impact the code
size but also the size of the exchanged messages. When using raw
public keys (instead of certificates) the "certificate" size was
reduced from 475 bytes to 163 bytes (using an RSA-based public key).
Note that the SubjectPublicKeyInfo block does not only contain the
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raw keys, namely the public exponent and the modulus, but also a
small ASN.1 header preamble.
For the raw public key implementation the following components where
needed (in addition to a subset of the cryptographic support
functions):
Minimal ASN1 Parser: 3,232 bytes
The necessary support from the ASN1 library now only contains
functions for parsing of the ASN1 components of the
SubjectPublicKeyInfo block.
Generic TLS Library: 16,288 bytes
This size of this library was slightly enlarged since additional
functionality for loading keys into the bigint data structure was
added. On the other hand, code was removed that relates to
certificate processing and functions to retrieve certificate related
data (e.g., to fetch the X509 distinguished name or the subject
alternative name).
TLS Client Library: 4,528 bytes
The TLS client-specific code now contains additional code for the raw
public key support, for example in the ClientHello message. Most
functions were left unmodified.
5. Summary and Conclusions
TLS/DTLS can be tailored to fit the needs of a specific deployment
environment. This customization property allows it to be tailored to
many use cases including smart objects. The communication model and
the security goals will, however, ultimately decide the resulting
code size; this is not only true for TLS but for every security
solution.More flexibility and more features will ultimately translate
to a bigger footprint.
There are, however, cases where the security goals ask for a security
solution other than TLS. With the wide range of embedded
applications it is impractical to design for a single security
architecture or even a single communication architecture.
6. Security Considerations
This document discusses various design aspects for reducing the
footprint of (D)TLS implementations. As such, it is entirely about
security.
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7. IANA Considerations
This document does not contain actions for IANA.
8. Acknowledgements
The authors would like to thank the participants of the Smart Object
Security workshop, March 2012. The authors greatly acknowledge the
prototyping and implementation efforts by Pedro Moreno-Sanchez and
Francisco Vidal-Meca who worked as interns at Philips Research.
9. References
9.1. Normative References
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, April 2006.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security", RFC 4347, April 2006.
[SHA] National Institute of Standards and Technology, , "Secure Hash
Standard", FIPS 180-2, Aug 2002.
9.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
for Establishing a Secure Real-time Transport Protocol (SRTP)
Security Context Using Datagram Transport Layer Security (DTLS)",
RFC 5763, May 2010.
[RFC4785] Blumenthal, U. and P. Goel, "Pre-Shared Key (PSK)
Ciphersuites with NULL Encryption for Transport Layer Security
(TLS)", RFC 4785, January 2007.
[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
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Extensions: Extension Definitions", RFC 6066, January 2011.
[RFC3268] Chown, P., "Advanced Encryption Standard (AES)
Ciphersuites for Transport Layer Security (TLS)", RFC 3268, June
2002.
[RFC4101] Rescorla, E. and IAB, "Writing Protocol Models", RFC 4101,
June 2005.
[RFC4279] Eronen, P., Ed., and H. Tschofenig, Ed., "Pre-Shared Key
Ciphersuites for Transport Layer Security (TLS)", RFC 4279, December
2005.
[TLS-IANA] IANA, "Transport Layer Security (TLS) Parameters:
http://www.iana.org/assignments/tls-parameters/tls-parameters.xml",
Oct 2012.
[I-D.ietf-tls-oob-pubkey] Wouters, P., Tschofenig, H., Gilmore, J.,
Weiler, S., and T. Kivinen, "Out-of-Band Public Key Validation for
Transport Layer Security (TLS)", draft-ietf-tls-oob-pubkey-07 (work
in progress) February 2013.
[I-D.keoh-lwig-dtls-iot] Keoh, S., Kumar, S., and Garcia-Morchon, O.,
"Securing the IP-based Internet of Things with DTLS", draft-keoh-
lwig-dtls-iot-01, February 2013.
[I-D.gilger-smart-object-security-workshop] Gilger, J., and
Tschofenig, H., "Report from the 'Smart Object Security Workshop',
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Tschofenig, et al. Expires January 6, 2014 [Page 14]
Internet-Draft Hitchhiker's Guide to TLS / DTLS July 5, 2013
Authors' Addresses
Hannes Tschofenig
Nokia Siemens Networks
Linnoitustie 6
Espoo, 02600
Finland
Phone: +358 (50) 4871445
Email: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.priv.at
Sandeep S. Kumar
Philips Research
High Tech Campus 34
Eindhoven 5656 AE
NL
Email: sandeep.kumar@philips.com
Sye Loong Keoh
Philips Research
High Tech Campus 34
Eindhoven 5656 AE
NL
Email: sye.loong.keoh@philips.com
Tschofenig, et al. Expires January 6, 2014 [Page 15]
