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Protecting Computer Systems and Communication Networks


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One way of hiding information

Encoded visual information (top) is revealed by overlaying a second encoded transparency (bottom)


Upgrading the confidentiality and authenticity of data communications and of computer-stored information is a major goal of leading cryptography experts at the Weizmann Institute's Faculty of Mathematical Sciences.

By studying and improving encryption techniques, they are developing new tools to ensure that computer files cannot be altered without detection and unauthorized users do not enter the system. By designing unforgeable digital identification systems, they are enabling verification of the authenticity of computer-to-computer communications and of network users. Institute computer scientists also investigate the theory of cryptographic transformations and random number generation, expanding basic knowledge in the field.

Before coming to the Institute in 1982, Prof. Adi Shamir was one of the developers of the extremely sophisticated RSA public key system. This benchmark cryptographic approach is currently used in many commercial software products and in secure telephone and network systems. In Rehovot, he and Dr. Amos Fiat designed a method that provides identification, authentication and signature facilities for digital communications, enhancing computer security. The procedure was patented by the Institute's Yeda Research and Development Co. and is presently used in various applications, including the programming of "smart cards" to ensure that only authorized subscribers can access satellite pay-TV.

"Zero-knowledge interactive proofs," a theoretical concept that underlies the Fiat-Shamir approach, was designed by Prof. Shafi Goldwasser when she was at MIT, working with her colleagues there and at the University of Toronto. This technique enables, among other things the transmission of an identification password in a way that provides no information about that password to an unauthorized eavesdropper. The wide applicability of zero-knowledge proofs was shown by Goldwasser's colleague Prof. Oded Goldreich, then also at MIT, who studied this with MIT and Berkeley scientists.

Goldwasser and Goldreich, both now at the Weizmann Institute, are improving the encryption of computer files, so that encrypting small changes in a large file does not require rescrambling the complete file. This advance may speed the use of scrambling to foil the spread of computer viruses or for preparing multiple authenticated documents. Goldreich is also developing ways to disseminate database information through multiple computers under different auspices, so that the database owner cannot record the information being requested.

The security risks associated with data transmission over public communication lines are also being addressed by Dr. Moni Naor. Such communication interactions include bank and computer-purchase transactions, as well as the transmission of medical records, proprietary data, and telecommunications. Naor is designing improved cryptographic schemes for dealing with these issues.

He also investigates "secret-sharing," techniques in which multiple keys held by different people are required to read or write confidential information. This idea is similar to the use of multiple signatures on checks. Naor and Shamir have recently implemented one of their concepts by designing a secret-sharing scheme for encrypting visual information.

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