Showing papers on "Cryptography published in 1976"

New Directions in Cryptography

Abstract: Two kinds of contemporary developments in cryptography are examined. Widening applications of teleprocessing have given rise to a need for new types of cryptographic systems, which minimize the need for secure key distribution channels and supply the equivalent of a written signature. This paper suggests ways to solve these currently open problems. It also discusses how the theories of communication and computation are beginning to provide the tools to solve cryptographic problems of long standing.

Stream/block cipher crytographic system

Abstract: The system disclosed comprises a dual function cryptographic system capable of operating in either a stream or block cipher mode. Further, with minimal alteration the system is capable of performing either encoding or decoding functions. The system requires three inputs, the first of which is the raw data, and the second two inputs comprise a first and a second unique user supplied key. One of the keys is utilized to control a permutation function for both the stream and block cipher mode and the other key is combined directly with the data in the block cipher mode prior to a series of non-linear transformations. In the stream encipherment mode of operation the second key is entered in its entirety into the system where it is successively and continuously transformed as a function of said first key whereby the function of said system becomes a pseudo-random number generator whose output is serially combined with the raw data to form the stream enciphered cryptogram.

Key controlled block-cipher cryptographic system employing a multidirectional shift matrix

Abstract: A cryptographic system for enciphering a block of binary data under the control of a unique key consisting of a set of binary symbols. A clear message represented in binary data format is transformed into a cipher message (and vise versa) by operating on blocks of clear information utilizing the operations of directional shifting of a derivative form of said clear data in a multidimensional matrix shifting and storage device. Further, cryptographic power is introduced to the system by performing a non-affine substitution operation during a shift operation on segments of information stored in said matrix. The shifting function, as well as the substitution function, is a function of said unique key. The system is further mathematically invertible, that is, the same hardware may be utilized for both encipherment and decipherment by merely reversing the sequence of operations.

Cipher computer and cryptographic system

Abstract: A system for the protection of stored and transmitted data including a random access memory accessed by counters and used for encrypting and decrypting signals in a cryptographic system using stream and block ciphers.

Encryption-based protection protocols for interactive user-computer communication

Abstract: This thesis develops a complete set of protocols, which utilize a block cipher, e.g., the NBS data encryption standard, for protection interactive user-computer communication over physically unsecured channels. The use of the block cipher protects against disclosure of message contents to an intruder, and the protocols provide for the detection of message stream modification and denial of message service by an intruder. The protocols include facilities for key distribution, two-way login authentication, resynchronization following channel disruption, and expedition of high priority messages. The thesis presents designs for modules to implement the protocols, both in the terminal and in a host computer system, and discusses the results of a test implementation of the modules on Multics.

Privacy and Security Issues in Information Systems

Abstract: A law now in effect in the United States requires protection of individual privacy in computerized personal information record-keeping systems maintained by the federal government. Similar laws apply in certain state and local governments. Legislation has also been introduced to extend the requirements for privacy protection to the private sphere. Central in privacy protection are the rights of an individual to know what data are maintained on him, challenge their veracity and relevance, limit their nonroutine use or dissemination, and be assured that their quality, integrity, and confidentiality are maintained. In all computer systems that maintain and process valuable information, or provide services to multiple users concurrently, it is necessary to provide security safeguards against unauthorized access, use, or modifications of any data file. This difficult problem has not yet been solved in the general case. Computer systems must also be protected against unauthorized use, disruption of operations, and physical damage. The growing number of computer applications involving valuable information or assets plus the growing number of criminal actions directed against computer applications and systems or perpetrated by using computers underscore the need for finding effective solutions to the computer security problem. In the future, concerns for privacy and security must become integral in the planning and design of computer systems and their applications.

The application of cryptography to data base security

Abstract: The application of cryptographic transformations for the purpose of enhancing the security in data base systems is discussed. These transformations have been recognized in the past as a valuable protection mechanism but their relation to data base security has not been identified. The major reason is the lack of a suitable data base model for investigating the questions of security and cryptography. A multi-level model of a data base is presented in this paper. This model helps to understand the connection between the data base structure and the cryptographic transformations applied to the data base. It is shown that cryptographic transformations can be applied between the different levels of the data base. Several types of these transformations are identified and the possible ways of using and controlling them are also discussed. The multi-level model can provide a useful framework for further research in the area of cryptography and data base security.

Cryptography using modular software elements

Abstract: Protection of information within a computer/communication system can be provided through reversible cryptographic transformation of the information itself into a form that can be returned to usable form only through use of control information known as "key."It is not necessary, in order to achieve access control, that the encryption algorithms, random number generator, or system organization be kept secret; in fact, a basic requirement of modern cryptographic technology is that it must be effective although a would-be penetrator is assumed to have full access to all of that information and the facilities and competence to apply it. Only the key can be assumed to be, and must be, physically secure.The building-block approach outlined makes use of pre-programmed software elements for providing all specialized algorithms, including the Proposed Federal Data Encryption Standard (DES), together with necessary nonnumeric generalized support routines for use with application programs written in conventional procedural higher languages (FORTRAN, COBOL, etc.). Both Strong Algorithm and Long Key methods can be used as required by security-level-vs-cost tradeoff considerations.This method is useful in conjunction with specialized hardware; for testing of programs and hardware; in some cases instead of hardware; and can support multiple-level security applications.The entire scheme, including the Tausworthe-Lewis-Payne bitwise linear recurrence modulo 2 quasirandom number generator, is based irrespective of hardware type on a standardized 64-bit data element.

Analysis of secret functions with application to computer cryptography

Abstract: In computer cryptography we cannot avoid that data and the corresponding encrypted data can be read by an outside observer. The information contained in these observations may be used to decrypt parts of encrypted data or ultimately to identify the key in the cryptographic transformation. In this paper we have analyzed this situation using the concepts of information theory. The result shows that in most cases it is theoretically possible for an outside observer to identify the key after very few observations. As this must be avoided we have to rely on computational complexity in the process of deriving the key. This is achieved by using one-way functions which are practically impossible to invert.

Digital encoding for secure data communications

Abstract: : This thesis is concerned with the use of the digital computer to realize cryptography. Three cryptographic systems: simple substitution, pseudo-random cipher (polyalphabetic cipher), and data-keyed cipher, are designed, implemented through computer programming, and evaluated. A suitable cyclic error correcting code is designed to encode these systems for transmission. The code is tested by simulating a noisy channel.

Cryptographic Digital Communication

Abstract: This paper reviews the fundamentals of cryptographic digital systems and defines and discusses the two basic types of ciphers. The remainder of this article examines the word and bit error rates in digital al communication systems with block or stream ciphers. Upper bounds and ensemble averages of the error rates are obtained for both ciphers. The effect of modulation type on the degradation in communication system performance caused by the addition of cryptography is analyzed. A comparison is made between block and stream ciphers with respect to their effects on degradation.

Address security concepts for mobile-telephone service

Abstract: Various levels of protection from unauthorized use of a mobile-telephone service can be provided where the exchange for the service is under stored-program control. The security techniques that provide this protection can be upgraded on a per-subscriber or per-system basis as the incidence of unauthorized use increases. The "ultimate" arrangement provides for the encryption of variable passwords. Proper protection of auxiliary storage devices precludes compromise of the cipher-keys assigned to individual mobile units. The techniques that apply and, in particular, those that provide for better security, are more readily implemented in a system with common channel signaling where signaling speeds are considerably faster than those that are used in present-day practice.