Securing communications requires the establishment of cryptographic keys, which is challenging in mobile scenarios where a key management infrastructure is not always present. In this paper, we present a protocol that allows two users to establish a common cryptographic key by exploiting special properties of the wireless channel: the underlying channel response between any two parties is unique and decorrelates rapidly in space. The established key can then be used to support security services (such as encryption) between two users. Our algorithm uses level-crossings and quantization to extract bits from correlated stochastic processes. The resulting protocol resists cryptanalysis by an eavesdropping adversary and a spoofing attack by an active adversary without requiring an authenticated channel, as is typically assumed in prior information-theoretic key establishment schemes. We evaluate our algorithm through theoretical and numerical studies, and provide validation through two complementary experimental studies. First, we use an 802.11 development platform with customized logic that extracts raw channel impulse response data from the preamble of a format-compliant 802.11a packet. We show that it is possible to practically achieve key establishment rates of ~ 1 bit/sec in a real, indoor wireless environment. To illustrate the generality of our method, we show that our approach is equally applicable to per-packet coarse signal strength measurements using off-the-shelf 802.11 hardware.

/pdf/radio-telepathy-extracting-a-secret-key-from-an-2kp0ofwwoc.pdf

Radio-telepathy: extracting a secret key from an unauthenticated wireless channel

This index covers all technical items - papers, correspondence, reviews, etc. that appeared in this periodical during 2000, and items from previous years that were commented upon or corrected in 2000. In the case of magazines, departments and other items may be also covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author’s name. The primary entry includes the coauthors’ names, the title of the paper or other item, and its location, specified by the publica tion abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author’s name, the publication abbreviation, month, and year, and inclusive pages. Subject cross-references are included to assist in find ing items of interest. Note that the item title is found only under the primary entry in the Author Index.

IEEE Signal Processing Magazine Vol. 17

Improved estimation performance using known linear constraints

Parallel saturating multioperand adders significantly improve the performance of global system for mobile (GSM) speech coders by giving compilers and assembly language programmers the ability to parallelize loops containing saturating dot products, while maintaining GSM compliant results. This paper presents four designs for parallel saturating multioperand adders. These designs have at most one carry-propagate adder on their critical delay path, yet produce the same results that would be obtained if the additions were performed serially with saturation after each addition. The four parallel designs offer tradeoffs in terms of area, worst case delay, and dot product latency. Compared to a 5-input serial design, the 5-input parallel designs have delays up to 3.51 times shorter.

/pdf/design-alternatives-for-parallel-saturating-multioperand-4cdg0hklfd.pdf

Design alternatives for parallel saturating multioperand adders

The processing delay is a serious constraint for speech communication. A one-way end-to-end delay of more than 150 ms can severely degrade the quality of real-time conversations. The components of the total system delay includes the speech frame size, the look ahead, other algorithmic delays, multiplexing delay, processing delay for computation, and transmission delay. At the transcoder rate adaptor unit (TRAU), the only delay that can be manipulated is the processing delay. The TRAUs are generally positioned remote to the base transceiver station (BTS). The channel codec units (CCUs) are located in the BTS. In general, 16 kbit/s traffic channels can be used for full rate speech between the TRAU and BTS. By putting the TRAU remote to the BTS, DSPs for speech coding can be utilized more efficiently to cut system cost. High performance DSPs, such as the Lucent DSP16000, can be used to further cut the cost per speech channel. This article presents an implementation of GSM enhanced full rate (EFR) codec on the Lucent Technologies' DSP16000. The original European Telecommunications Standards Institute (ETSI) C code has been restructured to address the issues of MIPS (million instructions per second), RAM usage, and processing delay. We give a performance overview of vocoder implementations on some existing fixed-point DSPs and discuss the architecture of the DSP16000. Details on how the ETSI C code is restructured are presented. The DSP16210 implementation results are then discussed.

High-performance DSPs

An implementation of GSM EFR using traditional single MAC DSPs (DSP1600) takes 24 MIPS to run a single speech channel. Lucent DSP16000 is a dual MAC high performance DSP. Analysis has shown DSP16000 code can run GSM EFR at 10 MIPS per channel with the same program space as DSP1600. The code has been re-structured to minimize the delays and RAM usage for multi-channel transcoder/rate adapter units (TRAU) applications. For a 100 MIPS DSP16210 running 6 EFR speech channels, DSP16210 code takes 15.7 K words of RAM with 3.2 ms maximum delay for the encoder and 0.5 ms for the decoder. Without re-structuring, the numbers are 27 K, 15.4 ms and 1.5 ms respectively. This makes the DSP16000 very attractive for TRAU applications. The initial implementation runs at 12.8 MIPS per channel with 19.3 K words of RAM, 4.7 ms maximum encoding delay and 0.5 ms maximum decoding delay for 6 speech channels.

GSM EFR implementation for TRAU application on DSP16000

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GSM EFR implementation for TRAU application on DSP16000