| 1. |
- Granlund, Gösta H.
(författare)
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A Nonlinear, Image-content Dependent Measure of Image Quality
- 1977
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, considerable research effort has been devoted to the development of useful descriptors for image quality. The attempts have been hampered by i n complete understanding of the operation of the human visual system. This has made it difficult to relate physical measures and perceptual traits.A new model for determination of image quality is proposed. Its main feature is that it tries to invoke image content into consideration. The model builds upon a theory of image linearization, which means that the information in an image can well enough be represented using linear segments or structures within local spatial regions and frequency ranges. This implies a l so a suggestion that information in an image has to do with one- dimensional correlations. This gives a possibility to separate image content from noise in images, and measure them both.Also a hypothesis is proposed that the visual system of humans does in fact perform such a linearization.
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| 2. |
- Blom, Rolf, et al.
(författare)
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Data Network Security : Part I Problem Survey and Model
- 1977
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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.
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| 3. |
- Ingemarsson, Ingemar
(författare)
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Encryption in Data Networks with Application to Teletex
- 1978
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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.
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| 4. |
- Ingemarsson, Ingemar, et al.
(författare)
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Computer Security 1981
- 1976
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The goal of COMPUTER SECURITY 1981 is to prediet the demand for protection of eleetronic data processing (EDP) and for the information processed. To predict the future demands on computer security we have discussed the issue with several people involved in one way or another with EDP. These discussions, our own knowledge other background material have been the material for discussions amongst the authors. The results are divided into two parts. In the first part (section 4) we have been as objective as possible. In the latter part (section 5) we have discussed the differences between the results in section 4 and our own opinion as proffessional researchers.In addition the report covers a summary of how EDP is used 1981 and a section describing the structure of the security field (which we have used in the interviews) and an outline of the investigation.
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| 5. |
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| 6. |
- Blom, Rolf
(författare)
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Bounds on key equivocation for simple substitution ciphers
- 1979
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Ingår i: IEEE Transactions on Information Theory. - : IEEE. - 0018-9448 .- 1557-9654. ; 25:1, s. 8-18
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Tidskriftsartikel (refereegranskat)abstract
- The equivocation of the key for a simple substitution cipher is upper and lower hounded, when the message source is memoryless. The hounds are shown to be exponentially tight. The results are compared with random ciphering. It is observed that the exponential behavior of the equivocation of the key is not determined by the redundancy in the message source, but by the symbol probabilities which are closest in a certain sense.
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| 7. |
- Blomberg, Mats, et al.
(författare)
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Statistical analysis of speech signals
- 1970
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Ingår i: STL-QPSR. ; 11:4, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- This is a condensed report of a thesis study carried out at the Department of Speech Communication in 1970, The purpose was to determine, for continuous speech, peakfactor, formfactor, long-time average spcctrum of voiced and voiceless sections separately, spectral density at different voice intensity level s r dist r ib~l t iono f the speech-wave amplitude, statistics on pause lengths and long-time average RMS of the speech wave. All tasks have been solved using the CDC computer of the Department.
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| 8. |
- Clayton, R, et al.
(författare)
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Absorbing boundary conditions for acoustic and elastic wave equations
- 1977
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Ingår i: Bulletin of The Seismological Society of America (BSSA). - : Elsevier BV. - 0037-1106 .- 1943-3573. ; 67:6, s. 1529-1540
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Tidskriftsartikel (refereegranskat)abstract
- The two dimensional elastic wave equations are used to model wave propagation in mediums with large or unbounded domains. In order to numerically simulate those problems the equations have to be put on the computer and artificial boundary conditions that allow minimal wave reflection must be introduced. These boundary conditions are well known in the literature as absorbing or radiating boundary conditions. They have been of interest to physicists and meteorologists for some time. In this paper three different methods for deriving radiating boundary conditions for the elastic wave equations are presented. One of these techniques gives exact absorbing boundary conditions for both P (longitudinal) and S (transverse) waves generated from a surface source. From this, approximate absorbing boundary conditions are derived. These conditions are easy to employ in finite difference codes.
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| 9. |
- Edvardsson, Bo, 1944-, et al.
(författare)
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A method for evaluation of metric properties of response scales
- 1976
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Ingår i: Quality and quantity. - Amsterdam : Elsevier. - 0033-5177 .- 1573-7845. ; 10:3, s. 241-249
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Tidskriftsartikel (refereegranskat)abstract
- The metric properties of five different response scales in measurment of attitudes, interests and personality traits are studied with an experiment group (N = 97) and a control group (N=40). The scales were different in how equal the distances between the response alternatives were.
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| 10. |
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