SPEDA 2010 – August, 23-25, 2010, Atlanta, GA, USA A. De Benedictis, A. Gaglione, N. Mazzocca Securing a Re-Taskable Sensing System Seclab Group – ://.

SPEDA 2010 – August, 23-25, 2010, Atlanta, GA, USA

A. De Benedictis, A. Gaglione, N. Mazzocca

Securing a Re-Taskable Sensing System

Seclab Group – http://www.seclab.unina.itDipartimento di Informatica e SistemisticaUniversità degli Studi di Napoli Federico IIVia Claudio, 21 – 80125 Napoli – ItaliaEmail: {alessandra.debenedictis, andrea.gaglione, nicola.mazzocca}@unina.it

1st International Workshop on Security and Performance in Emerging Distributed Architectures (SPEDA 2010)

August 23-25, 2010, Atlanta, GA, USA

http://www.seclab.unina.it/

http://www.seclab.unina.it/


About me

Alessandra De Benedictis

Ph. D. Student in Computer and Control Engineering at the

Department of Computer Science and System of the University of Naples

Federico II

[email protected]

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http://www.dis.unina.it/

http://www.dis.unina.it/

SPEDA 2010 – August, 23-25, 2010, Atlanta, GA, USA 3

Outline

Overview of security issues in sensor networks and background description

Introduction of a secure-layer to guarantee security requirements

Design and implementation details

Conclusions and future works


Motivation and security challenges in sensor networks

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Openness of wireless channels lets anyone be able to monitor or participate in communications

WSN applications require security mechanisms WSN features:

Very limited resources limited memory and storage space power limitations

Unreliable communication unreliable transfer conflicts (due to the broadcast nature of WSN) latency

Unattended operations exposure to physical attack remote management makes impossible to detect physical

tampering and physical maintenance issues


Desired security requirements

Desired properties of a secure sensor network communication architecture

Data authentication allows a receiver to verify that data really was sent by the claimed

sender Broadcast authentication

Data confidentiality protect information traveling through the network

Data integrity ensures the receiver that the received data has not been altered in

transit by an adversary achieved through data authentication

Data freshness implies that the data is recent ensures protection against replay attack

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Symmetric vs AsymmetricCryptography

Limited computational complexity, well suited for resource constrained devices such as sensor nodes but...

Key management is a fundamental concern

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Alice Bob

plaintext plaintextencryption ciphertext decryption

Alice Bob

plaintext plaintextencryption ciphertext decryption

Bob’s Public

Key

Bob’s Private Key

Symmetric Key Encryption (SKE) Public Key Cryptography (SKC)

Stronger degree of security than SKE schemes, greater flexibility and manageability but also..

Higher computation and storage requirement

…recent works demonstrated the feasibility of using Elliptic Curve Cryptography (ECC) schemes on sensor platforms, due to their fast computation, small key size and compact signatures features.

Such schemes have been proved to guarantee an equivalent security degree then other SKC schemes (such as RSA) while adopting smaller keys and requiring slighter computations.


Tenet: a re-taskable sensingsystem (1/2)

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The Tenet system is an architecture for tiered sensor networks, proposed by the Uiversity of LA (UCLA), consisting of:

motes: simple sensor nodes processing locally-generated sensor data

masters: relatively unconstrained 32-bit platform nodes, performing multi-node data fusion and complex application logic

Since masters have relatively plentiful processing and storage resources, it is possible to implement more sophisticated applications, such as cryptographic algorithms, by exploiting their capabilities


Tenet: a re-taskable sensingsystem (2/2)

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And return responses

Motes process data,

Applications run on masters, and masters task motes

periodic(1 min) -> sample(TEMPERATURE) -> Send()

A task is a linear data flow program consisting of a sequence of tasklet implementing such functionality as timers, sampling, data compression, thresholding, statistical operations, and other forms of simple signal processing.

Masters can then fuse the results, re-task motes or trigger

other sensing functionalities

Example of task

The tasking system enables an easier application development and a significant code reuse.

Mote functionality is limited to executing tasks and returning responses, thus enabling energy-efficient operations.


Proposal

Enhancement of the Tenet system, by introducing a hybrid cryptosystem which aims to:

1. implement a mechanism for key exchanging between master and motes

2. achieve broadcast authentication of tasking messages by a master to the motes

3. achieve end-to-end encryption, integrity and freshness of response messages sent by motes to the master

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Enhanced Tenet software architecture (1/2)

10 Master side

Improvement of the master side: at application level:

- introduction of the ECC Library to perform ECC operations

- addition of the pubKeyExchange element to the Tasking Library;

- modification of the TenetAPI in order to implement the digital signature of task messages sent from masters to motes

at OS level:

- integration of a cryptographic system, with the management of the keyfiles containing the secret keys shared between the master and each of the motes

Tenet ApplicationsECC

Library

Tasking Library

+ pubKeyExchange element

+ modified TenetAPI

TinyOS_system-Minisec

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Key store

Application layer: includes Tenet applications running on masters, and the Tenet Tasking Library, which implements a collection of composable tasklet.

OS layer: implemented by TinyOS


Enhanced Tenet software architecture (2/2)

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Mote side

Improvement of the mote side by adding: at application level: the new tasklet

pubKeyExchange to the Mote Tasking Library, that aims to perform ECC security operations according to the ECDH key agreement technique

at OS level: integration of a cryptographic system, with the management of the keyfile containing the secret key shared between the master and the mote

Mote Tasking Library

+ TinyECC library

+ pubKeyExchange tasklet

+ modified TaskInstaller component

TinyOS_system-Minisec

Ap

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Key file

OS

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Adopted technologies

TinyOS and MiniSec: MiniSec provides a secure network layer by modifying the TinyOS network stack:

GenericComm – generic network stack AMStandard – Active Message

transmissionProvides data confidentiality,

authentication and replay protection provides for authentication and secrecy

with a few block cipher calls (OCB mode)

better security and low energy consumption

Implementation for Telos motes 300 bytes of RAM, 3KB of code memory

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TinyECC: a configurable library for ECC operations in wireless sensor networksIncludes support for the ECC

schemes: ECDH - key agreement scheme ECDSA - digital signature scheme ECIES – encryption scheme

Easily integrated in sensor networks applications

It has been tested on MicaZ, TelosB and Imote2 platforms running TinyOS


1 - Key agreement

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Achieved via Tenet tasking system by adding a new tasklet which performs ECC security operations according to the ECDH key agreement tecnique

pubKeyExchange(PPx, PPy) ->Send()


2 - Broadcast authentication

Broadcast tasking messages from master to motes must be authenticated in such a way each mote can verify the identity of the master node: master node signs tasking messages with its own private key and sends them to motes together with the signature. on mote side the signature is verified with the master public key.

Achieved by implementing the ECDSA scheme by using the primitives provided by TinyECC.

Constraints: during the initialization phase of the system the master should generate a key pair (private key – public key) and store its private key in the ECC Library. each mote should be preloaded with the public key of the master

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3 - End-to-end confidentiality, integrity and freshness of response messages

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Achieved by opportunely integrating the MiniSec security layer into the Tenet system:

plain task

Encrypted response message

shared key

MASTER MOTE

Motes perform encryption of outgoing task response messages which are identified with a specific tag ;

Master decrypts incoming task response messages identified with the above mentioned specific tag


Conclusions and future works

We have proposed the design of a hybrid cryptosystem aimed to secure the Tenet architecture.

We have combined symmetric and asymmetric cryptographic schemes in order to achieve key exchange mechanisms (through the definition of a specific tasklet), end-to-end encryption, integrity and freshness of response packets sent from motes to the master, and broadcast authentication of tasking messages coming from the master to motes

In Future works we plan to set up a more complete testbed for the evaluation of our schemes in terms of achieved security level, energy consumption and performances. Furthermore we intend to port our code to TinyOS 2.x in order to be compliant with Tenet-t2 release as well as to port it to other sensor platforms.


Thanks for your kind attention

For any questions contact us

SPEDA 2010 – August, 23-25, 2010, Atlanta, GA, USA A. De Benedictis, A. Gaglione, N. Mazzocca Securing a Re-Taskable Sensing System Seclab Group – ://.

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