ISSN:1124-318X    

DOI:10.1002/ett.4460050402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460050403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460050404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIt is shown that the techniques of source coding (or “data compression”) can be usefully applied in cryptography. Five source coding schemes (Shannon‐Fano coding, Huffman coding, Lynch‐Davisson coding, Elias‐Willems coding, and Lempel‐Ziv coding) are reviewed and their characteristics delineated. It is then shown how the last three of these schemes, which are of the universal source coding type, can be advantageously used to create strongly‐ideal ciphers, to perform “universal” homophonic substitution, to test random bit generators, and to strengthen running‐key generators

ISSN:1124-318X    

DOI:10.1002/ett.4460050405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractHash functions were introduced in cryptology in the late seventies as a tool to protect the authenticity of information. Soon it became clear that they were a very useful building block to solve other security problems in telecommunication and computer networks. This paper sketches the history of the concept, discusses the applications of hash functions, and presents the approaches that have been followed to construct hash functions. In addition, it tries to provide the information which is necessary to choose a practical hash function. An overview of practical constructions and their performance is given and some attacks are discussed. Special attention is paid to standards dealing with hash functions.

ISSN:1124-318X    

DOI:10.1002/ett.4460050406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIn the traditional scenario in cryptography there is one sender, one receiver and an active or passive eavesdropper who is an opponent. Large bank transactions require two people to sign, implying two senders. So the power to generate a valid transaction is shared. Threshold cryptography allows one to share the power of a cryptosystem. Threshold cryptosystems are distinct from threshold schemes in which the power to regenerate a secret key is shared. A normal threshold scheme is not directly suited for threshold signatures. Using a threshold scheme directly would require the shareholders to send their shares to a trusted person who would apply the cryptosystem for them. But the use of such a trusted person violates the main point of threshold cryptography. We motivate the need for treshold cryptosystems, overview the research in the field, and give some simple examples. We will conclude by giving a list of open problems.

ISSN:1124-318X    

DOI:10.1002/ett.4460050407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractSubliminal channels were devised by Simmons in 1978 to demonstrate a fundamental flaw in a protocol the U.S. was considering using to allow the U.S.S.R. to verify U.S. compliance with the terms of the SALT II treaty. The examples given of such channels were more in the nature of existence proofs than feasible communication channels until 1984 when it was shown that most digital signature schemes could be caused to host subliminal communications hidden in the digital signatures. Almost all of these subliminal channels, however, had several shortcomings. In order for the subliminal receiver to be able to recover a subliminal message, it was apparently necessary for him to know the transmitter's (the signer's) secret key. This meant that the subliminal receiver had to be given the capability to utter undetectable forgeries of the transmitter's signature. Also, only a subset of the natural message set could be communicated subliminally and some of those that could be transmitted were computationally infeasible for the subliminal receiver to recover. A digital signature standard (DSS) has recently been adopted by the U.S. government (May, 1994) which like most other digital signature schemes also permits subliminal communications to be concealed in signatures. Remarkably though, the subliminal channels in the DSS avoid all of the shortcomings that limit the usefulness of these channels in other digital signature schemes. This paper briefly describes the setting for the discovery of subliminal channels and then in some detail, the nature and shortcomings of the subliminal channels in the El Gamal digital signature scheme ‐ to which the DSS is closely related. Finally, to make clear what a remarkable coincidence it is that the apparently inherent shortcomings present in subliminal channels realized in the El Gamal scheme can all be overcome in channels realized in the DSS, each of the channels is analyzed in detail in both schemes. The inescapable conclusion, though, is that the DSS provides the most hospitable setting for subliminal communications discovered to dat

ISSN:1124-318X    

DOI:10.1002/ett.4460050408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper describes the structure of a signal interpolator chip to be used in medium‐to‐high data rate digital modems, based on the so‐called “Systolic Macrocells” design style. In particular, we focus on a third‐order polynomial interpolation algorithm, as a good trade‐off between the contrasting needs of high accuracy and low complexity/cost. We also present a concise description of the architecture of the chip through a functional description of the main basic systolic macrocells it is composed of. Despite the apparent complexity of the architecture, the basic cells of each bit‐level systolic array are remarkably simple and homogeneous: they are mainly composed by delays and summing elements such as full and half adders, so that their realization does not represent a difficult design task. The interpolator chip has been completely laid out assuming a 1.2 μ m CMOS technology and occupies a silicon area of 5 × 4.5 mm2, pad included. In particular, we envisage an operating clock frequency of 70 MHz, so that the chip can process sequences of 8 bit words at the rate of 17.5 MSamples/s with a power supply requirement o

ISSN:1124-318X    

DOI:10.1002/ett.4460050409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe transmission of digital HDTV signals on satellite channels in the 20–30 GHz band is studied with the aim of designing an Italian domestic satellite, both for the exchange of programs among production centers and for direct broadcasting to end‐users. Previous work on the definition of the system architecture and of the payloads is first briefly summarized. The transmission impairments due to the interfered environment are then analyzed in detail and simulation studies are reported. The results confirm the choices made for the link budgets during the system configuration design. Experimental tests carried out both with laboratory simulators and with the Olympus European satellite are finally descri

ISSN:1124-318X    

DOI:10.1002/ett.4460050410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper proposes a new multimode communication service, denoted as Remote Expert Consultation Service (REC‐Service) which determines the way group teleworking is realized among distributed entities (workstations, data bases, etc) during a conference for medical diagnosis. The REC‐Service organizes the involved operations into five different types, called Conferencing Modes (CM), where each CM yields a traffic with variable attributes and requires of the network a special quality of service. Moreover, the structure of a Broadband user‐Network Interface Unit (BNIU) is defined. BNIU statistically multiplexes the traffic of the entities working in different CMs into an Integrated Broadband Communication (IBC) network. The maximum number of entities served per BNIU and the bandwidth usability have been calculated for several operating modes by modelling the BNIU as a queueing system and by applying special quality criteria, delay demands and traffic assump

ISSN:1124-318X    

DOI:10.1002/ett.4460050411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY