Symmetrische kryptographische Verfahren (German Edition)

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Customers who bought this item also bought. Page 1 of 1 Start over Page 1 of 1. A Textbook for Students and Practitioners. See all Product description. To get the free app, enter mobile phone number. STOC, and show that a large class of random-oracle transformations are not sound. This affects the Encrypt-with-Hash transformation Bellare et al. An often repeated criticism of random-oracle uninstantiability results is that the schemes only fail to be secure because they are designed to do so and, furthermore, their artificial design conflicts good cryptographic practice see, for example, Koblitz and Menezes; Journal of Cryptology, Similar criticism can be voiced also for our counterexamples to the general applicability of the above mentioned random-oracle transformations.

While this does not refute the mathematical validity of such uninstantiability results, we do, however, also present a very different counterexample to the soundness of the random oracle methodology: We note that the same holds also for our negative results for UCEs. In summary, we develop techniques to work with obfuscation which allow us to show that the existence of indistinguishability obfuscation implies that various random oracle techniques may lead to insecure schemes.

Our results suggest, once again, that we should be careful with random oracle proofs and we hope that they spark further research to overcome the necessity to use random oracles in the first place.

Concerning the latter, we make first steps by proposing new and widely applicable UCE notions together with standard-model candidate constructions showing that UCEs may, indeed, be a viable alternative to the use of random oracles. Random Oracles in the Standard Model. Downloads Downloads per month over past year. Print Impressum Privacy Policy.

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NP oder Zahlentheorie z. Dieses Orakel wird auch Random Oracle genannt. Wenn wir nun kryptographischen Verfahren vertrauen, die beweisbar sicher sind, sollten wir dann auch Verfahren vertrauen, die relativ zu einem Random Oracle beweisbar sicher sind? Ein solches Resultat ist insbesondere von z. Im Falle des Public-key Verfahrens von Canetti et al. Aber sollten wir, wenn ein Verfahren in der Tat sicher ist, nicht in der Lage sein den Grund der Sicherheit, bzw.

Code Obfuscation hat eine lange Tradition in der Informatik insbesondere der Software Entwicklung wurde jedoch meist als Heuristik betrachtet. Unter anderem geben wir die ersten Standardmodell-Konstruktionen d. Dies betrifft unter anderem die Encrypt-with-Hash Transformation Bellare et al. In a further embodiment, the service data are transmitted from the computer along with the collected response messages to the data center of the customer contract partner.

The customer media to be authenticated in the data center in each case by comparing the authentication document in the encrypted response message part of the customer medium with a comparison value, which is generated elliptic curve cryptography based on the received by the computer service data and included in the encrypted response message part of the customer medium public key of the customer medium. In one embodiment, the media clients are identified in the data center each by comparing a public key of the customer medium contained in the encrypted response message part of the customer medium with data stored in a customer database of customer public keys media.

The signals received from the computer running portion data is associated with a particular by the public key of the customer medium customer identification.

In further embodiments, the encrypted symmetric key with the response message portion is also generated from status data of the customer medium and a sequence number. Die Dienstleistungsdaten umfassen beispielsweise eine Rechneridentifizierung, eine Dienstleistungsidentifizierung und aktuelle Zeitangaben. The service data include, for example, a computer identification, a service identification and actual timings.

Aus den Dienstleistungsdaten wird ein Hashwert erzeugt und die Aufforderungsmeldung wird aus dem Hashwert der Dienstleistungsdaten erzeugt. A hash value is generated from the service data and the request message is generated from the hash value of the service data. In addition to a method for detecting a custom purchase of services of a service provider system, the present invention relates also to the following interacting components: In this case, the computer system, the computer and at least one customer medium together form a computer-implemented service acquisition system for acquiring a customer-specific purchasing of services, for example, a computer-implemented detecting system for detecting the customized use of public transport.

In one embodiment of the processor of the client media is also programmed to use in the encrypted response message part of a public key of the customer medium as customer identification, which is generated from the data stored in the customer medium private key using the elliptic curve cryptography, and encrypted with the symmetric key response message part also from to generate status data of the customer medium and a sequence number.

Customer medium, decrypting contained in the reply messages encrypted response message parts of the customer media each case by means of the symmetric key of the customer medium and authenticating the customer media respectively by comparing an authentication document contained in the response message part of the customer medium with a comparison value which elliptic curve cryptography based on received from the computer service data and contained in a response message part of the customer medium public key of the customer medium is created.

In one embodiment of the processor of the computer system is also programmed to compare the customer media each by comparing a public key of the customer medium contained in the encrypted response message part of the customer medium with data stored in a customer database public keys of the customer media and from the computer received service data a by the public key assigned to the customer media specific customer identification.

The computer program product for controlling the computer system comprises a non-transient computer-readable medium having stored thereon computer program code that is configured to control a processor connectable to a communication system for data exchange with a computer of a service system computer system such that the processor executes the steps of: The computer of the service system for detecting the custom purchase of services is provided with a communication system for radio-based data exchange with customers media from customers in the service system and at least comprises a processor that is programmed to perform the steps of: In one embodiment, the computer is arranged as an on-board computer in a vehicle and run for detecting a custom to use the public transport facility.

The processor of the on-board computer is also programmed to include in the service data drive section data with an on-board computer identification, a drive section identification and a current time value to generate a hash value from the journey section data, and to generate the request message from the hash value of the drive section data. The computer program product for controlling the computer comprises a non-transient computer-readable medium having stored thereon computer program code that is configured to control a processor of the computer provided with a communication system for radio-based sending data to clients media clients in a service system such that the processor performs steps of: An embodiment of the present invention by way of example will be described.

The example of the embodiment is illustrated by the following attached figure: In der In the Figur 1 Figure 1 bezieht sich das Bezugszeichen ES auf ein computerimplementiertes Erfassungssystem zur Erfassung des kundenspezifischen Bezugs von Dienstleistungen eines Dienstleistungssystems.

Im Erfassungssystem ES sind drei Parteien beteiligt: Subsequently, the detection system will be described using the example of the detection of the customized use of a public transport VM, for example, railway, tram, metro, cable car, bus, boat, etc. The customer medium KM is designed as a portable, mobile customer identification medium, for example in the form of a smart card, a "dongle" or designed in another form custom hardware tokens.

The customer medium KM includes a processor and a communication module for radio-based data exchange with the on-board computer BR. For wireless data communication with the on-board computer BR for service acquisition, the communication module includes a transceiver, for example, in the MHz range.

Depending on the embodiment, moreover, a radio receiver for receiving activation signals in the transport VM, for example in the range 6. The feeding of customers KM medium via a rechargeable battery internal. The on-board computer BR includes one or more processors and is equipped with a communication system for radio-based data exchange with the customer media KM, for example, several transceiver via a communication network, such as an Ethernet, the processors are connected to the onboard computer BR respectively.

The data center RKV comprises one or more computer systems each having one or more processors and is connectable to a communication system, for example, a communication system having a GSM or UMTS or another wireless network. For data exchange with the on-board computers BR.

The computer systems respectively, the processors of the computer center RKV, the on-board computer BR respectively its processors and the processor of the client KM medium are controlled by computer program code stored on computer-readable, non-transient storage media. Diese Computerprogrammprodukte sind fest oder entfernbar mit den betreffenden Prozessoren verbunden. These computer program products are fixedly or removably connected to the respective processors.

The computer program code is executed to control the respective processors so as to perform the detection method described below. In step S0 for the detection of a service service data Dat BR generated by the on-board computer BR comprising drive section data in the present example. The service data respectively drive section data Dat BR comprise a computer identification, in particular an identification ID BR of the on-board computer BR of transport VM, a service identification, in particular a journey section number FAN BR of the currently traveled by the transport VM drive section, current time information, for example, the current date and the current time and other information.

Elliptic curve-based cryptography enables low-power Proto Great with short data messages between the parties. In the Diffie-Hellman protocol known basic protocol is implemented a key agreement between two parties in principle. Based on this basic protocol two protocols are derived, which combined realize the desired cryptographic properties, ie a nichtabstreitbare authentication of related performance by the customer medium KM and an anonymous not trackable transmission of data to the customer contractor KV. For this purpose, the customer KM medium and in the second protocol c y by the public key Pub KV of the customer contract partner KV is replaced in the first protocol c x by the public key Pub KM.

The interweaving of these two protocols derived occurs as will be described in detail. In step S2, the prompt message c BR from the on-board computer BR is radio-based system in the service, that is in transport VM emitted. By regular broadcast transmitting the invitation message c BR is communicated to the point on the curve changing from drive section to drive portion as a challenge to be detected simultaneously to all customers in the transport media KM KM.

With the thus-formed document authentication r KM can be demonstrated later, that the customer medium KM at the time of creation of the service data respectively drive section data Dat BR has been detected by the respective on-board computer BR.