Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [NTRU Security Suite

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [NTRU Security Suite Proposal Highlights] Date Submitted: [March 8, 2002] Source: [Daniel V. Bailey, Product Manager for Wireless Networks and Ari Singer, Principal Engineer] Company [NTRU] Address [5 Burlington Woods, Burlington, MA 01803] Voice:[(781) 418-2500], FAX: [(781) 418-2507], E-Mail:[dbailey@ntru.com] Re: [Draft P802.15.3/D09, P802.15-02-074r1 802.15.3 Call For Proposals for a Security Suite] Abstract: [This presentation presents highlights of NTRU’s proposal for security suite for the 802.15.3 draft standard.] Purpose: [To familiarize the working group with the NTRU proposed security suite.] Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.

2. Use Cases Directed Connectivity • 802.15.3 is a high data-rate, personal-range MAC and PHY • Most compelling use case is directed connectivity for consumer rich media devices • 55 Mbps (and up!) per second is needed by things that stream… • DVD players • HDTVs, wireless projectors • Digital camcorders • …and things that “check in/out” content • Digital cameras • Personal MP3 players • The things using 1394 and USB today!

3. Use Cases What About These Devices? • Consumer multimedia devices • Small form factor • User interface varies from a PC to a receiver to a digital camera to a speaker • Setup has to be simpler than cables!!! • Today consumers are fatigued by the effort needed to set up the average home entertainment center • Operate in ad-hoc mode today • Plug your digital camera in where/when you need it • No Internet/backend connectivity can be assumed • Severe cost/power constraints in this market • How much extra power does a camcorder have?

4. Use Cases Security and 1394 • Today, security is a non-issue for the consumer • Just plug it in! • No threats against the consumer • Threats addressed by 5C are against content owners, not consumers – DRM belongs outside the MAC/PHY • 1394 asks one question of its user: Is THIS the device I want in MY network NOW? • Plugging in answers “yes.” • So the user is trusted to make this decision

5. Use Cases Security and 1394 • What does that buy me in terms of security? • Everything I need! • Security Goal #1: Only devices I want can join my network/Is this the device I want in my network now? • Security Goal #2: Only devices I want can read my data • Security Goal #3: Only devices I want can send data to my devices • How do we make this happen in 802.15.3 just like 1394?

6. Use Cases Doing Security in 802.15.3 • The KISSS Principle: Keep it Simple and Secure, Stupid! • Complexity in security is BAD. It’s more stuff to get wrong. • 1394’s security is Real Simple, but plenty for the application. • Complexity is expensive. • Let’s start with unsecured 802.15.3 and add the security features we need

7. Use Cases Securing an 802.15.3 Piconet • An 802.15.3 piconet has a star topology • One device, the PNC, allocates bandwidth • So it decides who can talk over the radio • Security Goal #1: Only devices I want can join the network • The PNC makes this decision in an unsecure piconet • Applying the KISSS principle, it will do so in a secure piconet, too. • But how?

8. Use Cases Is This the Device I Want in My Network Now? • Devices or device manufacturers can’t answer this question for a user • So let’s have the PNC ask the user • At least one device in a crowd of consumer multimedia machines must have a rich enough user interface. • Ad hoc networks of speakers aren’t very interesting • Might as well decide to save the answer if it’s “yes.” • PNC hears from a device over the radio and prompts • But wait! • How do I know the device isn’t lying about who it is?

9. Use Cases Why Not Use Digital Certificates? • Because they: • Don’t answer the relevant question: Is THIS the device I want in MY network NOW? • Require sophisticated user intervention in order to be secure • Requires user to map certificate to device • Inaccurate user intervention compromises security • Are complicated to issue and manage • Add cost to manufacturers • Add complexity: Complex systems are harder to secure Certificates have their uses…just not in a WPAN

10. Use Cases Is the PNC Talking to the Right Device? • The real question is: Is the PNC hearing over the radio from the same device I’m trying to add to my network? • Actual identity of a device isn’t needed. • With 1394, I just know it’s “this one.” • How do we get the user to point and say “this one?” • Best way depends on the application, but we can rely on the DME to ask the user to introduce the devices • Bring them close together and they can whisper • PNC asks the user to confirm some information the device sent • PNC asks the user to confirm the distance between the devices • Device presents the PNC with a signed statement about its identity

11. Use Cases Is the Device Talking to the Right PNC? • While we’re at it, how does the device know the PNC is the right one? • All the same ways, it turns out…

12. Use Cases Device Confirmation • Once the user points and says “this one,” it’d be nice for the devices to be able to prove to each other they really are “this one.” • How do we do that? • How about if I send you a secret only you can read and you prove to me you could read it? • That’s the essence of a Challenge-Response Protocol • Alice sends Bob a challenge only he can read. • Bob responds showing he could read it

13. Use Cases Challenge-Response Protocols • One type of authentication protocol • Often uses public-key cryptography • They’re well-studied • You find them in textbooks, web browsers, … • Applying the KISSS Principle, let’s pick one off the shelf and gently modify it to suit our needs • We picked SSL, found in every web browser • Let’s also pick the most-efficient public-key algorithms to hold down costs • We picked NTRUEncrypt, cause it’s the most efficient. • More about NTRUEncrypt later!

14. Use Cases My Secure Piconet • PNC and device now can tell if they’re talking to the right one. • But how do I know they’re still talking to the right one?

15. Use Cases Integrity Protection • Once authentication is finished, any device can come along and pretend to be either the PNC or the device • How did the PNC know it was the right device? • It sent a challenge, which the device proved it knew. • So the device can just go on proving it still knows the challenge • That’s the essence of a Message Authentication Code (MAC) • Let’s just call it an Integrity Code (IC) so we don’t get confused • Applying the KISSS Principle, let’s pick one off the shelf and use it. • We picked Triple-DES cause it’s the most studied block cipher in the world and the most area efficient for these data rates

16. Use Cases My Secure Piconet • PNC and device now can tell if they started talking to the right one. • Now they can also tell if they’re still talking to the right one • All PNC-DEV commands protected with a unique integrity key only they share • All piconet data protected with a shared integrity key everyone in the piconet knows • But I don’t want other devices to hear my data traffic • 1394 protects me in this way

17. Use Cases Bulk Data Encryption • Anyone with a radio can hear all my data traffic • How do I keep it secret? • Use a symmetric cipher • Note: Not public-key! Symmetric ciphers are more efficient once we already share challenges • Applying the KISSS Principle, let’s pick one off the shelf and use it • We picked Triple-DES cause it’s the most studied block cipher in the world and the most area efficient for these data rates • Hey, wait, haven’t I heard that line before?

18. Use Cases Triple-DES • You can use the same gates to implement encryption as well as integrity. • Or you can use different algorithms for encryption and integrity • The KISSS Principle tells us that’s the thing to do • Synthesized with LeonardoSpectrum, you’ll need exactly 9796 gates. • Throughput is 2 bits/cycle for both encryption and integrity • To hit 55 Mbps, a 30 MHz clock is fine • Crypto-esoterica tells us we should encrypt first and then do integrity…

19. Use Cases My Secure Piconet • PNC and device now can tell if they started talking to the right one. • They can also tell if they’re still talking to the right one • Now outsiders can’t hear my data traffic • But how do devices get piconet-wide keys?

20. Use Cases Piconet-wide Key Distribution • How do devices get piconet-wide keys? • Well, how do they get piconet-wide guaranteed time slots? • The PNC allocates time slots, so applying the KISSS Principle, let it generate and distribute keys

21. Use Cases What if a Device Joins or Leaves? • Change the piconet keys • But how do I ensure only devices I want get the new keys? • PNC already shares unique keys with each device, so send the piconet-wide keys to each encrypted with their unique key

22. What About PNC Handover? • We’ve got two options • A device explicitly establishes trust (if it hadn’t already done so) with the new PNC • Could disrupt the piconet if some devices need user intervention! • A device trusts the new PNC because the old PNC trusts it • No disruption, but problematic • Since this is a PERSONAL Area Networking standard, it’s likely the DEV, the old PNC, and the new PNC will be trusting the same user • So let the user decide! • If I’m facilitating trust for all these devices, I don’t care who the PNC is. Let it hand off. • If I’m not facilitating this trust, I’d rather my devices ask before associating to a new PNC.

23. What Does a Device Need to Know? • A device has a public/private key pair, installed at provisioning time. • An authenticated device shares a unique DEK and DIK with the PNC agreed on during the authentication process • An authenticated device shares a different DEK and DIK with the rest of the piconet.

24. What Does a Device Need to Know? • A device keeps a table (access control list) of the other DEVs with which it has a trust relationship • A simple device only needs one entry: the PNC! • The public key itself need not be stored • The PNC will need storage for each associated DEV • Ideally, we’d like to put this in EEPROM • When the electricity goes out, I don’t want to have to reintroduce every device to the PNC

25. What Does a Device Need to Know? • Each device keeps some data about the current group keys • If the beacon has the same SSID and a greater time token, the time token is updated and the key is valid for that superframe • If the PNC ID and the PNC ID in the beacon are different, a new device is now PNC and the device attempts to authenticate to the new PNC

26. How Do We Protect the Beacon? • The beacon includes a Security Session ID (SSID) so devices know which piconet-wide key is in use • Beacon also includes a Time Token. It’s really a beacon counter to be used in all messages to prevent replay of messages in future superframes. • We use a message authentication code, or MAC. Let’s call it an integrity code. • The integrity code prevents an outside attacker from modifying data in the beacon.

27. How Do We Protect Commands? • 802.1x was broken due to failure to protect commands! • Commands are protected independently from each other. • Commands include the current SSID and time token that were sent in the protected beacon for group related commands. • Commands also include the counter from the peer relationship for key management commands.

28. The NTRU Hard Problem The hard problem underlying NTRU is the Shortest Vector Problem in lattices of high dimension Best Known Methods to Break: • NTRU and ECC are exponential (very slow) • RSA and DH are subexponential (faster)

29. Brief History of Lattice Problems Lattices, the SVP, and the CVP have been extensively studied for more than 100 years (Hermite 1870s, Minkowski 1890s,…). Best computational tool was developed by Lenstra, Lenstra, and Lovasz (LLL algorithm) in early 1980s. Improvements to LLL are due to Schnorr, Euchner, Horner, Koy, and others. Algorithms to find small vectors in lattices have been extensively studied because they have applications to many areas outside of cryptography, including physics, combinatorics, number theory, computer algebra,…. Contrast this with integer factorization (RSA) and elliptic curve discrete logarithms (ECC), where the only applications are to cryptography.

30. NTRU Security NOTE: 4 x 103 MIPS-Years = c. 1 year on a 450 MHz Pentium

31. Scrutiny and Standardization

32. Scrutiny • NTRUEncrypt has been widely studied since it was first announced in 1996 • Papers on NTRU techniques appear at every major cryptography conference • Nguyen and Stern (CaLC-2001): “this makes NTRU the leading candidate among knapsack-based and lattice-based cryptosystems, and allows high dimension lattices.” • Miccancio (IMAP 2002) observed that NTRU lattices are in Hermite Normal Form, the most secure form for a general lattice • NTRU encourages peer review • Challenge problems • Support to Crypto community (CaLC conference, etc)

33. NTRU Standardization work • IEEE P1363 • Draft of P1363.1 available on IEEE P1363 WG web site with NTRUEncrypt included • Vote on permanently including NTRUEncrypt passed at May 2001 meeting • Consortium for Efficient Embedded Security (CEES) • Draft of EESS #1 standardizing NTRUEncrypt currently available from http://www.ceesstandards.org • Drafts include complete specification, encodings, certificate formats, etc. • VHN (Versatile Home Networking) • NTRU included in EIA/CEA-851

34. NTRU Standardization work • IETF • TLS: NTRU ciphersuites proposed May 2001. • Expected to proceed to Informational RFC. • PKIX: “Supplemental Algorithms for PKI” Internet Draft • Edited by NTRU, includes NTRUEncrypt • Also includes new US Government algorithms: DSA2, SHA-256… • WAP • NTRU active participants in WSG

35. Performance on a Microcontroller • Speakers will have an 8051 if they’re lucky • Microcontrollers vary widely, so here’s three implementations of NTRUEncrypt:

36. Comparison on a Microcontroller • For comparison, the top microcontroller has a 50,000 gate RSA/ECC coprocessor • 028r3-TG3-Coding-Criteria.ppt gives the following cost/power guidance: • In 0.18 micron technology, 100,000 gates cost 20 cents • Power is dissipated at a rate of 0.018 mW/(MHz*kgates) * This is a software implementation of NTRUEncrypt and so requires no additional gates beyond the microcontroller

37. Comparison in Hardware • What if you need NTRUEncrypt in hardware? • This is a complete implementation, including SHA-1

38. Summary • Our proposal: • Fulfills the requirements set out: • Security Goal #1: Only devices I want can join my network • Security Goal #2: Only devices I want can read my data • Security Goal #3: Only devices I want can send data • Respects network design principles • Keeps to the KISSS Principle • Reduces cost for manufacturers • Reduces complexity for implementers • Enables deployment of the widest range of devices • Is simple, complete and secure.