The Energy Cost of SSL in Deeply Embedded Systems

As the number of potential applications for tiny, battery-powered, “mote”-like, deeply embedded devices grows, so does the need to simplify and secure interactions with such devices. Embedding a secure web server (capable of HTTP over SSL, aka HTTPS), enables these devices to be monitored and controlled securely via a user-friendly, browser-based interface. This paper presents the first empirical energy analysis of the Internet’s dominant security protocol, SSL, on highly constrained devices. We have enhanced Sizzle, our tiny-footprint HTTPS stack, with energy conserving features and measured its performance on a Telos mote. We show that the key exchange phase, which consumes much more energy than bulk encryption and authentication, amortizes well over the transmission of a few kilobytes of application data. Such amortization is easily attained with features like session reuse and persistent HTTP(S), both of which are supported by Sizzle. The extra energy cost of encrypting and authenticating application data with SSL is around 15%. With the addition of an application-level, duty-cycle based approach to low-power listening for incoming services requests, a pair of alkaline batteries can power Sizzle for over a year under a variety of application scenarios. email addresses: [email protected] [email protected] © 2008 Sun Microsystems, Inc. All rights reserved. The SML Technical Report Series is published by Sun Microsystems Laboratories, of Sun Microsystems, Inc. Printed in U.S.A. Unlimited copying without fee is permitted provided that the copies are not made nor distributed for direct commercial advantage, and credit to the source is given. Otherwise, no part of this work covered by copyright hereon may be reproduced in any form or by any means graphic, electronic, or mechanical, including photocopying, recording, taping, or storage in an information retrieval system, without the prior written permission of the copyright owner. TRADEMARKS Sun, Sun Microsystems, the Sun logo, Java, Sun Ray, and Solaris are trademarks or registered trademarks of Sun Microsystems, Inc. in the U.S. and other countries. All SPARC trademarks are used under license and are trademarks or registered trademarks of SPARC International, Inc. in the U.S. and other countries. Products bearing SPARC trademarks are based upon an architecture developed by Sun Microsystems, Inc. UNIX is a registered trademark in the United States and other countries, exclusively licensed through X/Open Company, Ltd. For information regarding the SML Technical Report Series, contact Jeanie Treichel, Editor-in-Chief .All technical reports are available online on our website, http://research.sun.com/techrep/. The Energy Cost of SSL in Deeply Embedded Systems∗ Vipul Gupta, Michael Wurm Sun Microsystems Laboratories 16 Network Circle, UMPK16-160 Menlo Park, CA 94025 http://research.sun.com/projects/crypto [email protected], [email protected]