Cryptography – Particular algorithmic function encoding
Patent
1993-11-29
1995-05-02
Swann, Tod R.
Cryptography
Particular algorithmic function encoding
380 30, 380 42, H04K 100
Patent
active
054127289
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the field of the security protection of digital data.
2. Discussion of Prior Art
It finds a general application in the protection of digital data, and in particular in operations such as authentication, sealing, enciphering/deciphering, electronic signature and generation of secret codes.
A distinction is made between two main families of enciphering means:
The asymmetric-key enciphering means, such as those using the RSA public-key algorithm, RSA standing for "RIVEST, SHAMIR, ADLEMAN" allow some of the security protection operations mentioned above to be carried out.
However, such devices exhibit drawbacks.
In fact, they require machines capable of carrying out calculations on 512-bit data, since, below this size, they are not considered to be sufficiently safe, especially for individualizing user stations.
Moreover, the large number of operations necessary for the various enciphering operations makes the implementation of such algorithms very cumbersome.
The symmetric-key enciphering means, such as those using the DES algorithm, DES standing for "DATA ENCRYPTION STANDARD", also allow the majority of the data security protection operations mentioned above to be carried out.
The symmetric-key enciphering algorithms are much faster than the asymmetric-key algorithms.
In the symmetric-key enciphering means, a distinction is made between block algorithms and stream algorithms.
For example, for an authentication operation in which a server wishes to ensure that it is corresponding with an authorized user, the operation of the symmetric-key block algorithm is as follows.
The user executes the security algorithm in order to supply a result R wishes a function of the data to be security protected and of the secret key. For its part, and symmetrically, the security module of the server carries out a similar calculation giving a result R'. The server then checks the consistency of the result R with the result of its own calculation R'.
Cryptography experts are in agreement in saying that such algorithms cannot be considered as sufficiently safe if the data blocks are of less than 64 bits.
The stream enciphering algorithms rest on another principle which is both simple and recognized as being the safer.
It is a matter of adding a random string, bit by bit, to the text to be enciphered. This is the means, for example, which is mentioned as being in use between the Kremlin and the White House.
However, encryption algorithms of the the symmetric stream type exhibit drawbacks.
In fact, the random string has to be as long as the text to be enciphered. This results in problems in transporting the enciphering key.
One solution to these problems consists in distributing a short secret key between the two extremities, allowing a pseudo-random sequence to be generated.
Such enciphering algorithms exist and generally use shift registers, looped back over maximum periods and combined by boolean operations.
However, such enciphering algorithms are complicated to implement.
SUMMARY OF THE INVENTION
The invention remedies these drawbacks by proposing a device for security protection of digital data, particularly allowing all the security protection operations mentioned above to be performed, no longer using enciphering algorithms but simple cryptography tools which are easy to implement, necessitating a reduced number of operating conditions and using elementary instructions existing on the majority of digital data processing devices.
The object of the invention is also to reduce the role of the enciphering keys, the latter functionally having only a role which is identical to that of the data to be processed.
Finally, the object of the invention is to decline an operating mode into a plurality of operating modes by modifying a restricted number of initialization data.
The invention concerns an electronic digital data processing device, including: data.
According to the principal characteristic of the invention, the processing means comprise: quasi-
REFERENCES:
patent: 5222139 (1993-06-01), Takaragi et al.
patent: 5261003 (1993-11-01), Matsui
patent: 5301235 (1994-04-01), Shimada
IBM Technical Disclosure Bulletin, vol. 22, No. 2, Jul. 1979 New York US, pp. 650-651, Ehrsam et al, "Block Chaining using plaintext--et al".
Besnard Christian
Martin Joel
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