George B. Purdy, Gustavus J. Simmons, and James A. Studier. A software protection scheme. In Proc. 1982.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....the paper. The Appendix contains a proof that the protocols cannot be subverted to copy licenses. 2 Copy protection with smart cards The only theoretically secure copy protection arrangement is to deliver the code in encrypted form and to decrypt and execute it inside a tamper resistant processor [14, 15, 6]. In practice, such processors cannot be mandated and the code is exposed to insecure user equipment. Therefore, copy protection is always to some extent security by obscurity. In practical protection mechanisms based on a hardware token, a user license is embodied by a copy resistant piece of ....

George B. Purdy, Gustavus J. Simmons, and James A. Studier. A software protection scheme. In Proc. 1982.

....an old session key and use it for a new authenticated session [8] see also the discussion above) the authentication protocol of an early draft version of the international standard X. 509 [15] which contained a similar flaw [6] as well as a software licensing system of Purdy, Simmons and Studier [36], which could be circumvented by an attacker by combining and reusing recorded messages [40] These examples show the need for formal validation of cryptographic protocols as protocol flaws can not be sufficiently analyzed using non formal methods. For this purpose a variety of approaches has ....

G. B. Purdy, G. J. Simmons, and J. A. Studier. A Software Protection Scheme. In Proceedings of the 1982.

....protocol can lead to an undesirable situation, such as compromising a key. Although this method can not guarantee absolute safety, it works very well in identifying specific protocol flaws. The method has been successfully used to find various known flaws in protocols such as the [42] 19] 43] [44] and [45] No previously undetected vulnerabilities in well known protocols have been discovered using this method. The tool s applicability is limited by the operators it supports (conventional and public key encryption, exclusive or and limited finite field exponentiation) 3.2.3. Algebraic ....

Purdy G., Simmons G., Studier J. A Software Protection Scheme. In: Proceedings of the 1982 IEEE Symposium on Security and Privacy. IEEE Computer Society Press, pp. 99103

....that had received extensive hand analysis. Examples include the Needham Schroeder key distribution protocol [30] which was found by Denning and Sacco [10] to allow an intruder to pass off an old, compromised session key as a new one, the software protection scheme of Purdy, Simmons, and Studier [33], for which Simmons [35] showed how an intruder could combine previously generated messages in such a way that the system could be induced to grant unauthorized access to software, and a protocol in the CCITT X.509 draft standard [9] for which Burrows, Abadi, and Needham [6] showed that an ....

G. B. Purdy, G. J. Simmons, and J. A. Studier. A Software Protection Scheme. In Proceedings of the 1982 Symposium on Security and Privacy, pages 99--103. IEEE Computer Society Press, April 1982.

.... the Needham Schroeder key distribution protocol [23] which was found by Denning and Sacco [7] and Bauer, Berson and Feiertag [1] to be vulnerable to various kinds of replay attacks that can be used whenever old keys are compromised, the software protection scheme of Purdy, Simmons, and Studier [25], for which Simmons [28] showed how a penetrator could combine previously generated messages in such a way that the system could be induced to grant unauthorized access to software, and a protocol in the CCITT X.509 draft standard [5] which was shown by Burrows, Abadi, and Needham [4] to be ....

....by a penetrator that, when input, could result in a violation of the protocol s security requirements, even when the penetrator is a legitimate user or set of users of the system who may have access to one or more processors. Indeed, it was a flaw of this sort in an earlier, similar, protocol [25], that lead to the development of the selective broadcast protocol. We use the notation e(X,Y) to mean the encryption of word Y with key X, and d(X,Y) to mean the decryption of word Y with key X. Multiple encryption is represented by the use of nested functions; e.g. if we encrypt word Z with key ....

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G. B. Purdy, G. J. Simmons, and J. A. Studier. A software protection scheme. In Proceedings of the IEEE Symposium on Security and Privacy, pages 99--103, Oakland, CA, 1982. IEEE Computer Society Press.

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