Walter Leonard Tuchman

A cryptographic key management scheme for implementing the data encryption standard

Data being transmitted through a communications network can be protected by cryptography. In a data processing environment, cryptography is implemented by an algorithm which utilizes a secret key, or sequence of bits. Any key-controlled cryptographic algorithm, such as the Data Encryption Standard, requires a protocol for the management of its cryptographic keys. The complexity of the key management protocol ultimately depends on the level of functional capability provided by the cryptographic system. This paper discusses a possible key management scheme that provides the support necessary to protect communications between individual end users (end-to-end encryption) and that also can be used to protect data stored or transported on removable media.

IV. `Hellman presents no shortcut solutions to the DES¿

Prof. Martin Hellman presents no shortcut solutions to the Data Encryption Standard; the time-memory tradeoff is just one of many key-message exhaustion techniques. Therefore when he says, ¿DES is only marginally secure today and will be totally insecure within ten years,¿ he is totally wrong.

Time-Notch Filtering

A method is described for measuring low-level time-truncated signals by using narrow-bandwidth synchronous time-notch filters. These filter systems, intended for use with ordinary narrowband receivers or field intensity meters, provide a means of isolating time-truncated signals of interest from adjacent interfering signals. In addition, the important property of near optimum sensitivity (approaching that of a matched filter) is discussed, and the laboratory results of a low-frequency time-notch filter covering the 500-Hz to 2-MHz range are given.