Fall 2005

Unless indicated otherwise, the CryptoSeminar is being held in the Atwater Kent building on the WPI Worcester campus. The Atwater Kent building is at the intersection of Salisbury Street and the extension of West Street (labeled "Private Way"). See directions to campus.

The talks are 30-45 minutes long and are open to everyone.

Refreshments are usually being served 15 minutes before the talk. There is no fee and no formal registration. If you are attending a Seminar for the first time, a short e-mail to Profs. Berk Sunar or Bill Martin, saying that you would like to attend, would be appreciated.

Jitter in Oscillators with 1/f Noise Sources and Application to True RNG for Cryptography.

Chengxin Liu, Analog and Mixed IC Laboratory, Worcester Polytechnic Institute
Monday, December 19, 2005, 10:00am, Atwater Kent Labs, WPI, Room 233

Abstract

In the design of voltage-controlled oscillators (VCOs) for communication systems, timing jitter is of major concern since it is the largest contributor to the bit-error rate. The latest deep submicron processes provide the possibility of higher oscillator speed at the cost of increased device noise and a higher 1/f noise corner. Therefore it is crucial to characterize the upconverted 1/f noise for practical applications.

This dissertation presents a simple model to relate the time domain jitter and frequency domain phase noise in the presence of non-negligible 1/f noise sources. It will simplify the design, simulation, and testing of the PLL, since with this technique only the open loop VCO needs to be considered. A ring oscillator and PLL design methodology is also developed by analyzing the upconverted thermal noise in time domain using a LTI model. The trade-off and relationship between jitter, speed, power dissipation and VCO geometry are evaluated for different applications. This model is supported by the measured data from 24 VCOs with different geometry fabricated in TSMC 0.18m process.

The theory developed in this dissertation is applied to the design of PLL- and DLL- based true random number generators (TRNG) for application in the area of smart cards. New architectures of dual-oscillator sampling and delay-line sampling are proposed for random number generation, which has the advantage of lower power dissipation and lower cost over the traditional approaches. Both structures are implemented in test chips fabricated in AMI 1.5m process. The PLL-based TRNG passed the NIST SP800-22 statistical test suite and the DLL-based TRNG passed the Diehard battery of tests with data streams over 80M bits.

Optimal Robust Codes with Equal Error Detecting Capabilities for all Errors.

Mark Karpovsky, Reliable Computing Lab, Boston University
Thursday, December 15, 2005, 2pm, Atwater Kent Labs, WPI, Room 218

Abstract

I will present a new class of optimal robust non-linear error-detecting codes with equal probabilities of error detection for all errors. These codes may be useful for error detection in communication and computation channels with unknown or non-stationary error distributions.

Let Fq = Fps be a linear space over Fp and C ∈ Fq be a code in Fq. Denote by Q(e)=|{v ∈ C | v+e ∈ C}| / |C|, where e ∈ Fq, e ≠ 0. (Q(e) is the probability of detection of error e by code C.) We will say that C is robust iff Q(e) is a constant for all e ≠ 0. I will describe the construction of optimal non-linear quadratic robust codes. (All linear codes are not robust.)

It will also be shown that any linear (n,k)-code V with k≥n/2 (not detecting |V|=pk errors) can be transformed into nonlinear quadratic systematic (n,k)-code CV (with the same n and k) which will not detect only pk-pk-(n-k) errors. These errors undetectable by CV form a (n-k) dimensional subspace in V.

I will talk also about application of the proposed robust codes for error detection in communications, computer memories and in the design of cryptographic devices (such as AES) resistant to differential fault attacks.

Cryptography for Ultra-Low Power Devices
Securing Ubiquitous Computing

Jens-Peter Kaps, Worcester Polytechnic Institute
Tuesday, December 6, 2005, 5pm, Atwater Kent Labs, WPI, Room 218

Abstract

Ubiquitous computing describes the notion that computing devices will be everywhere: clothing, walls and floors of buildings, cars, forests, the desert, etc. Ubiquitous computing is becoming a reality: RFIDs are currently being introduced into the supply chain. Wireless distributed sensor networks (WSN) are already being used to monitor wildlife and to track military targets. Many more applications are being envisioned. For most of these applications some level of security is of utmost importance. Common to WSN and RFIDs is that their power resources are severely limited. These are ultra-low power devices. The challenge is to provide light-weight cryptographic services for ultra-low power devices.

Most research groups are concerned with secure wireless communication protocols, others with efficient software implementations of cryptographic algorithms. There has not been a comprehensive study on hardware implementations tailored for ultra-low power applications. Our goal is to develop a suite of cryptographic functions for authentication, encryption and integrity that is specifically fashioned to the needs of ultra-low power devices.

This presentation gives an overview of our current work and its future direction.

Authenticating Pervasive Devices with Human Protocols

Stephen A. Weis, Massachusetts Institute of Technology
Thursday, September 22, 2005, 5pm, Atwater Kent Labs, WPI, Room 108

Abstract

Forgery and counterfeiting have emerged as serious security risks for low-cost pervasive computing devices. These devices lack the computational, storage, power, and communication resources necessary for most cryptographic authentication schemes. Surprisingly, low-cost pervasive devices like Radio Frequency Identification (RFID) tags share similar capabilities with another weak computing device: people.

These similarities motivate the adoption of techniques from human- computer security to the pervasive computing setting. We analyze a particular human-to-computer authentication protocol designed by Hopper and Blum (HB), and show it to be practical for low-cost pervasive devices.

The HB protocol is secure against passive eavesdroppers, but not active adversaries. We offer a new, augmented version of the HB protocol, named HB+, that is secure against active adversaries. HB+ is a novel, symmetric authentication protocol with a simple, low-cost implementation. We prove the security of the HB+ protocol against active adversaries based on the hardness of the Learning Parity with Noise (LPN) problem.

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