Cryptography – Particular algorithmic function encoding – Nbs/des algorithm
Patent
1987-11-18
1992-03-17
Buczinski, Stephen C.
Cryptography
Particular algorithmic function encoding
Nbs/des algorithm
380 4, 380 22, 380 25, 380 30, 34082531, 34032534, G06K 962, G06F 1214, G07F 710
Patent
active
050975048
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and a device for qualitative protection of digital data recorded on a medium that can be erased or modified.
The problem of protecting access to data that had been processed or was to be processed arose with the introduction of automatic data processing. Although effective solutions were found to this problem, notably with regard to the protection of on line data stored in the databases of large data processing systems, their implementation requires the use of very large scale data processing resources. Nevertheless, this type of protection cannot claim to be absolute, as recent spectacular intrusions into defense-related databases in various countries have shown. This type of intrusion, possible mathematically and in practice, is now revealing a problem of a different nature altogether in that such intrusions are usually "transparent", the skilled "hacker" being able to operate without leaving any trace or record revealing his identity. The risk actually run because of such intrusions involves not only access to confidential or secret information, unknown to the moral authority responsible for the corresponding databases, in the case where the qualitative integrity of the data is not compromised by the intrusion, but also the risk of destruction or modification of data, whether the hacker has any fraudulent intent or not. In particular, the trade press has drawn attention to a significant growth in "computer embezzlement" through simple intrusion into the data banks of finance and banking institutions followed by fraudulent modification or falsification of accounting data.
The results of various attempts to solve a related problem have recently been published, in particular in French patent application No 2 514 593.
In the technique described in the aforementioned patent application, a message whose content is to be acted on is first subjected to contraction by Hamming code type processing. A signature is then computed from the resulting contraction using an encryption algorithm, the encrypted signature having the same number of digits or characters as there are digits or characters in the contraction.
However, the technique described in the aforementioned patent application cannot claim to be usable for qualitative protection of digital data such as that contained in a database for the following two-fold reason.
There is no way that the contraction of the original message by linear processing such as the Hamming code could claim to constitute a unique representation of the original message, as different messages can generate the same contraction. Thus qualitative protection of text is not possible since in the final analysis two different messages can produce the same contraction and therefore the same signature.
Also, as the encryption sequence applied to the contraction to produce the encrypted signature is carried out within the circuitry of a protected memory card, the computation capacity of which is modest, the contraction and the encrypted signature cannot comprise more than six characters at the most.
An object of the present invention is to remedy the aforementioned disadvantages with a view to providing, in particular, since absolute protection of access to the on line data of databanks cannot be totally guaranteed, a means of preserving the integrity of digital data by qualitative protection of the data recorded on a medium that can be erased or modified.
Another object of the present invention is the implementation of a method and a device for qualitative protection of digital data in which a signature which is perfectly representative of a unique text or message and its author is placed on the medium on which the data is recorded in clear language, the signature constituting a seal.
Another object of the present invention is the implementation of a signature method and device whereby each different text has a signature for a determined key independent of the original text.
Another object of the present invention is, in the case of transmission of inf
REFERENCES:
patent: 4211919 (1980-07-01), Ugon
patent: 4656474 (1987-04-01), Mollier et al.
patent: 4796181 (1989-01-01), Wiedemer
Camion Paul
Goutay Jean
Harari Sami
Buczinski Stephen C.
Gregory Bernarr Earl
Infoscript
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