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Cracking DES : Secrets of Encryption Research, Wiretap Politics & Chip cracking Secrets of How federal Encryption Research agencies Wiretap Politics subuert & Chip Design priuacv e ELECTRONIC FRONTIER FOUNDATION Digitized by the Internet Archive in 2013 http://archive.org/details/crackingdessecreOOelec Cracking DES Cracking DES Secrets ofEncryption Research, Wiretap Politics & Chip Design Electronic Frontier Foundation Cracking DES: Secrets of Encryption Research, Wiretap Politics, and Chip Design by the Electronic Frontier Foundation With the exceptions noted, this book and all of its contents are in the public domain. Published in 1998 by the Electronic Frontier Foundation. Printed in the United States of America. No rights reserved. Every part of this book, except as noted below, may be reproduced, in any form or by any means, without permission in writing from the publisher. Because this material is in the public domain, permission to reproduce, use, copy, modify, and distribute this material for any purpose and without fee is hereby granted. The test-file, bootstrap, and bootstrap2 listings in Chapter 4 are Copyright © 1997 by Network Associates, Inc. These listings may be reproduced in whole or in part without payment of royalties. Chapter 10, Architectural Considerations for Cryptanalytic Hardware, is Copyright ©1996 by the authors, Ian Goldberg and David Wagner. It may not be reproduced without the permission of the authors, who can be reached at [email protected] and [email protected]. Chapter 11, Efficient DES Key Search: An Update, is Copyright © 1997 by Entrust Technologies. It may be reproduced in whole or in part without payment of royalties. Chapter 9, Breaking One Million DES Keys, is Copyright © 1986. Work done at the University of Leuven, Belgium, and supported by the NFWO, Belgium. It may not be repro- duced without the permission of the author, who can be reached at [email protected]. Distributed by O'Reilly & Associates, Inc., 101 Morris Street, Sebastopol, CA 95472. Printing History: May 1998: First Edition. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and the publisher was aware of a trademark claim, the designations have been printed in caps or initial caps. While many precautions have been taken in the preparation of this book, the publisher and distributor assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. This book is printed on acid-free paper with 85% recycled content, 15% post-consumer waste. O'Reilly & Associates is committed to using paper with the highest recycled content available consistent with high quality. ISBN: 1-56592-520-3 [9/98] Table of Contents Foreword ix Preface xiii 1: Overview /-/ Politics of Decryption 1-1 Goals 1-7 History of DES Cracking 1-8 EFF's DES Cracker Project 1-8 Architecture 1-9 Who Else Is Cracking DES? 1-16 What To Do If You Depend On DES 1-17 Conclusion 1-18 2: Design for DES Key Search Array 2-1 On-Chip Registers 2-1 Commands 2-4 Search Unit Operation 2-4 Sample Programming Descriptions 2-5 Scalability and Performance 2-9 Host Computer Software 2-9 Glossary 2-10 vi Table of Contents 3: Design for DES Key Search Array Chip-Level Specification 3-1 ASIC Description 3-1 Board description 3-3 Read and Write Timing 3-5 Addressing Registers 3-7 All-active Signal 3-7 ASIC Register Allocation 3-8 4: Scanning the Source Code 4-1 The Politics of Cryptographic Source Code 4-1 The Paper Publishing Exception 4-2 Scanning 4-4 Bootstrapping 4-5 5: Software Source Code 5-1 6: Chip Source Code 6-1 7: Chip Simulator Source Code 7-1 8: Hardware Board Schematics 8-1 Board Schematics 8-1 Sun-4/470 backplane modifications 8-10 PC Interfaces 8-12 Errata 8-13 9: Breaking One Million DES Keys by Yvo Desmedt 9-1 Abstract 9-1 Introduction 9-1 The basic idea 9-2 Details of such a machine 9-2 Obtained results and remarks 9-4 Conclusion 9-4 Acknowledgement 9-5 Table of Contents vii 10: Architectural Considerations for Cryptanalytic Hardware .. 10-1 Abstract 10-1 Introduction 10-1 Motivation 10-2 Related work 10-4 Technical Approach 10-6 Design and Analysis 10-8 Future work 10-23 Conclusions 10-23 Acknowledgements 10-24 Availability 10-24 References 10-24 — 11: Efficient DES Key Search An Update by Michael J. Wiener 11-1 Advancing Technology 11-2 Programmable Hardware 11-3 Conclusion 11-4 12: Authors 12-1 The Electronic Frontier Foundation 12-1 John Gilmore 12-2 Cryptography Research 12-2 Paul Kocher 12-3 Advanced Wireless Technologies 12-3 Foreword by Whitfield Dijfie In 1974 the Stanford computer science community ate at Loui's.* As I sat eating one evening in the fall, Butler Lampson approached me, and in the course of inquiring what I was doing, remarked that the IBM Lucifer system was about to be made a national standard. I hadn't known it, and it set me thinking. My thoughts went as follows: NSA doesn't want a strong cryptosystem as a national standard, because it is afraid of not being able to read the messages. On the other hand, if NSA endorses a weak cryptographic system and is discovered, it will get a terrible black eye. Hints that Butler was correct began to appear and I spent quite a lot of time think- ing about this problem over the next few months. It led me to think about trap- door cryptosystems and perhaps ultimately public-key cryptography. When the Proposed Data Encryption Standard was released on the 17th of March 1975,* I thought I saw what they had done. The basic system might be ok, but the keyspace was on the small side. It would be hard to search, but not impossible. My first estimate was that a machine could be built for $650M that would break DES in a week. I discussed the idea with Marty Hellman and he took it on with a vengance. Before we were through, the estimated cost had fallen to $20M and the time had declined to a day.* * Louis Kao's Hsi-Nan restaurant in Town and Country Village, Palo Alto t 40 Federal Register 12067 \ Whitfield Diffie and Martin E. Hellman. Exhaustive cryptanalysis of the NBS data encryption stan- dard. Computer, 10(6):74-84, June 1977. IX Foreword by Whitfield Diffie Our paper started a game in the cryptographic community and many papers on searching through DES keys have since been written. About three years after the publication of our paper, Robert Jueneman—then at Satellite Business Systems in McLean, Virginia —wrote "The Data Encryption Standard vs. Exhaustive Search."* This opus was substantially more optimistic about the chances for DES breaking. It predicted that by 1985 a half-million dollar investment would get you a DES key every hour and that by 1995, $10 million similarly spent would reduce that time to two seconds, an estimate remarkably close to one made fifteen years later. A decade later, Yvo Desmedt and Jean-Jaques Quisquater made two contibutions, one whimsical, one serious. Using a related "birthday problem" sort of approach, they proposed a machine for attacking many cryptographic problems at a timet. Their whimsical suggestion took advantage of the fact that the polulation of China was about the square root of the size of the DES key space.* The year 1993 brought a watershed. Michael Wiener of Bell-Northern Research (BNR) designed the most solid paper machine yet.S It would not be too far off to describe it as a Northern Telecom DMS100 telephone switch, specialized to attack- ing DES. What made the paper notworthy was that it used standard Northern Tele- com design techniques from the chips to the boards to the cabinets. It anticipated an investment of under a million dollars for a machine that would recover a key every three hours. A provocative aside was the observation that the required bud- get could be hidden in a director's budget at BNR. Finally, in 1996, an estimate was prepared by not one or two cryptographers but by a group later, and not entirely sympathetically, called the magnificent seven. 11 This estimate outlined three basic approaches loosely correlated with three levels of resources. At the cheap end was scrounging up time on computers you didn't need to own. In the middle was using programmable logic arrays, possibly PLA machines built for some other purpose such as chip simulation. The high end was the latest refinement of the custom chip approach. * R. R. Jueneman, The Data Encryption Standard vs. Exhaustive Search: Practicalities and Politics. 5 Feb 1981. f Yvo Desmedt, "An Exhaustive Key Search Machine Breaking One Million DES Keys", presented at Eurocrypt 1987. Chapter 9 of this book. t Jean-Jacques Quisquater and Yvo G. Desmedt, Chinese Lotto as an Exhaustive Code-Breaking Machine, Computer, 24(11): 14-22, November 1991. § Michael Wiener, "Efficient DES Key Search", presented at the Rump session of Crypto '93. Reprinted in Practical Cryptography for Data Internetworks, W. Stallings, editor, IEEE Computer Society Press, pp. 31-79 (1996). Currently available at ftp://ripem.msu.edu/pub/crypt/docs/des-key- search.ps. II Matt Blaze, Whitfield Diffie, Ronald L. Rivest, Bruce Schneier, Tsutomu Shimomura, Eric Thompson, and Michael Wiener. "Minimal key lengths for symmetric ciphers to provide adequate commercial security: A report by an ad hoc group of cryptographers and computer scientists", January 1996. Avail- able at http: //www. bsa.org /policy /encrypt ion /cryptographers .html. Foreword by Whitfield Dijfie Exhaustive key search is a surprising problem to have enjoyed such popularity.
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