| 1. |
- Blom, Rolf, et al.
(författare)
-
Data Network Security : Part I Problem Survey and Model
- 1977
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Data encryption and related methods may be used to preserve information security i n a data network. Here information security is defined as the degree to which the destruction, change or loss of information is presented. Information is defined as the content of the message represented by the data. The information in a block of data is unchanged if the intended result of the transmission of the block is obtained. This means for example that the original message reaches the correct destination where it is interpreted as intended. Undisturbed information does not, in general, require un disturbed data.The network is supposed to be a public network, accessed by many different users. We are interested in a well defined group of users who are communicating mainly among themselves. Different groups, however, are also allowed to communicate in a well defined manner. The logical structure of the communication within a group is star-shaped. The information communicated within the groups hall be protected against threats from other users of the network, from illegitimate users (wiretappers etc) and from members in the group. The structure of the threats is described in section 3 of this paper.The network itself and the requirement it imposes are supposed to be unchanged. Encryption and decryption are taking place outside the network. The encrypted data shall comply with the requirements of the network. The communication process in the group consists of time-limited messages which are essentially transmitted from one point to another in the network. This is the basis for the model of the communication which is described in section 4. The model, although simple, enables us to structure the problems in connection with encryption/decryption. This is done in section 5 and 6. The purpose of the paper is to form a basis for synthesis of security measures by means on cryptological methods. The analysis is general enough to be applied to any data network and any type of user group.
|
|
| 2. |
- Ingemarsson, Ingemar
(författare)
-
Encryption in Data Networks with Application to Teletex
- 1978
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- TELETEX is a new international telecommunication service for text communication between terminals capable of data storage and possibly integrated in a information processing system, [l]. The new service is intended to fill the same needs as does business mail. With regard to information security this means that the information handled by the TELETEX system shall not be unintentionally changed or destroyed or lost to an unintended receiver. Measures to prevent this are called information protection. (We prefer to use the terms information security and information protection rather than data security and data protection. The reason is that "data " in the sense of a string of symbol s may be lost without revealing the information represented by the data. This is for example the case when the data consists of encrypted information).One of the most efficient methods for information protection is to use encryption. This means that the information is transmitted using a ''language" which i s not understood by is efficiently protected against loss and in most cases also against undetected change. Cryptological methods can also be used to detect information destruction. In Section 2 of this report we discuss the basic problems involved with the use of encryption in data networks in general.In a separate report we discuss the possible threats to the information security in TELETEX. This leads to suggestions regarding suitable protection methods. Our standpoint is that TELETEX shall offer at least the same level of information security as does the established mail distribution system.
|
|
| 3. |
- Ingemarsson, Ingemar
(författare)
-
Några reflektioner kring elektroniska betalningsmedel
- 1979
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- De här nedskrivna tankarna är en frukt av diskussioner med bankfolk och datasäkerhetsforskare rörande olika problem med elektroniska betalningsmedel. De utgör ett försök att formulera de mest grundläggande egenskaperna i viss mån för betalningsmedel i allmänhet och för elektroniska i synnerhet. Syftet är att skapa diskussion kring de problem (främst säkerhetsproblem) som en allmän användning av elektroniska betalningsmedel kan ge upphov till.
|
|
| 4. |
- Dzonova, I., et al.
(författare)
-
A Comparative Study of the Labelling Algorithms for Solving the Problem of Maximum Flow in Networks
- 1978
-
Ingår i: Proceedings of Informatica 78. - Bled, Slovenia. ; , s. 120-121
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, the analysis of three labeling algorithms for finding the maximum flow in networks is presented. For each algorithm, a computer program is written and tested on networks. The comparison is made on the basis of the processing time and memory storage required for the implementation of each program. As a result, the relationship between the processing time required for each algorithm and the complexity of the networks is established.
|
|
| 5. |
- Haraldsson, Anders, 1946-
(författare)
-
A program manipulation system based on partial evaluation
- 1977
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Program manipulation is the task to perform transformations on program code, and is normally done in order to optimize the code with respect of the utilization of some computer resource. Partial evaluation is the task when partial computations can be performed in a program before it is actually executed. If a parameter to a procedure is constant a specialized version of that procedure can be generated if the constant is inserted instead of the parameter in the procedure body and as much computations in the code as possible are performed.A system is described which works on programs written in INTERLISP, and which performs partial evaluation together with other transformations such as beta-expansion and certain other optimization operations. The system works on full LISP and not only for a "pure" LISP dialect, and deals with problems occurring there involving side-effects, variable assignments etc. An analysis of a previous system, REDFUN, results in a list of problems, desired extensions and new features. This is used as a basis for a new design, resulting in a new implementation, REDFUN-2. This implementation, design considerations, constraints in the system, remaining problems, and other experience from the development and experiments with the system are reported in this paper.
|
|
| 6. |
- Mats, Cedwall, 1946-
(författare)
-
Semantisk analys av processbeskrivningar i naturligt språk
- 1977
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of the project described in this report is to study control structures in Natural Swedish, especially those occuring when tasks of algorithmic nature are described, and how to transform these specifications into programs, which can then be executed.The report describes and discusses the solutions that are used in an implemented system which can read and comprehend descriptions of patience (solitaire) games. The results are partly language dependent, but are not restricted to this specific problem environment.The system is divided into four modules. The syntactic module splits the sentence approximately to its component parts. In addition to the standard component categories, such as subject and predicate, every preposition is regarded as a component category of the sentence. The semantic analysis within a sentence works with a set of internallsation rules, one for each combination of a verb and a component part. The third module deals with the semantics on text level and integrates the representation of a sentence into the program code that is built up. The last module is an interpreter which can execute the programs representing patience games.
|
|
| 7. |
|
|
| 8. |
- Risch, Tore, 1949-
(författare)
-
Compilation of multiple file queries in a meta-database system
- 1978
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A meta-database system is constructed for describing the contents of very large databases. The meta-database is implemented as data structures in a symbol manipulation language, separate from the underlying database system. A number of programs are built around the meta-database. The most important program module is a query compiler, which translates a non-procedural query language called LRL into a lower level language (COBOL). LRL permits the specification of database retrievals without stating which files are to be used in the search, or how they shall be connected. This is decided automatically by the query compiler. A major feature of the system is a method, the Focus method, for compiletime optimization of these choices. Other facilities include the definition of "views" of the database; data directory services; authority codes; and meta-database entry and update.Design issues discussed include the decision to compile rather than interpret non-procedural query languages; the decision to separate the meta-database from the underlying database system; and the problem of achieving an architecture convertible to any underlying database system. Experience with one such conversion is reported.
|
|
| 9. |
- Risch, Tore
(författare)
-
REMREC - A program for Automatic Recursion Removal
- 1973
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- It is well known that recursive functions are very common in LISP. Recursive code is mostly the easiest to write and to analyse. However, situations often arise when it is preferable to let the computer work with non recursive functions. Examples of this are in compiled code and on stack overflow. It is then very often possible to remove recursion (at least partly) in the functions, without therefore introducing stacks in the new code.Remrec is a program, which automatically transfers some classes of recursive LISP functions into equivalent non recursive ones, without introducing stacks.
|
|
| 10. |
- Urmi, Jaak, 1944-
(författare)
-
A machine independent LISP compiler and its implications for ideal hardware
- 1978
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A LISP compiler is constructed without any a priori assumptions about the target machine. In parallel with the compiler a LISP oriented instruction set is developed. The instruction set can be seen as either an intermediarylanguage for a traditional computer oras the instruction set for a special purpose LISP machine. The code produced by the compiler is evaluated with regard to its static and dynamic properties. Finally some architectural aspects on LISP oriented hardware are discussed. The notion of segments with different word lengths, under program control, is developed and a proposed implementation of this is described.
|
|
