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In cryptography the standard model is the model that gives the adversary the strongest powers for attacking the cryptographic scheme at hand. Other names used ar bare model and plain model. The attacker is only restricted in a complexity theoretic sense, i.e. in the amount of computation he can do in a certain time interval. A polynomially bounded attacker can only do a polynomial amount of computation, and can thus not solve every problem instance of a super-polynomial problem. Exponential time is an important subset of super-polynomial time. The German Lorenz cipher machine, used in World War II for encryption of very high-level general staff messages Cryptography (or cryptology; derived from Greek κÏυπτός kryptós hidden, and the verb γÏάφω gráfo write) is the study of message secrecy. ...
In cryptography, an adversary (rarely opponent, enemy) is a malicious entity whose aim is to prevent the users of the cryptosystem from achieving their goal (primarily privacy, integrity and availability of data). ...
As a branch of the theory of computation in computer science, computational complexity theory describes the scalability of algorithms, and the inherent difficulty in providing scalable algorithms for specific computational problems. ...
In complexity theory, exponential time is the computation time of a problem where the time to complete the computation, m(n), is bounded by an exponential function of the problem size, n (i. ...
Cryptographic schemes are often based on the assumption that a certain problem, e.g. factorization, is super-polynomial. If such assumptions are the only assumptions made by the scheme, the scheme can be proven secure in the standard model. However at times it is convenient to limit some of the powers of the attackers. This can be done by introducing idealized objects that cannot be manipulated by the adversary. Two objects which are widely used for proofs in cryptography are a random oracle and a common reference string. These changes give rise to the random oracle model and the common reference string model. Often the standard model is negatively defined as the model that does not use these objects. Another widely used model is the public key infrastructure or PKI model. In mathematics, factorization or factoring is the decomposition of an object (for example, a number, a polynomial, or a matrix) into a product of other objects, or factors, which when multiplied together give the original. ...
In cryptography, a system is said to have provable security if its security requirements are stated formally in an adversarial model, as opposed to heuristically, and there is a proof (called a reduction) that these security requirements can be met provided that some well studied cryptographic primitive (such as RSA...
A random oracle is a theoretical model of a perfect cryptographic hash function. ...
In cryptography, a public key infrastructure (PKI) is an arrangement that binds public keys with respective user identities by means of a certificate authority (CA). ...
There exists a fundamental difference between the random oracle model and other models, in that random oracles cannot be implemented by real world functions[1]. A common reference string is just a sequence of bits and consequently can exist--even if it is impossible for two parties that have never met each other and know nothing about each other to agree on such a string by means of a cryptographic protocol alone, when communicating over an adversary controlled network. For instance these parties could meet, throw some coins, and record the results. They could also register their identities and public keys with the certificate authority of a PKI, and then run a cryptographic coin flipping protocol. This argument also shows that the PKI model is at least as powerful as the CRS model. Coin flipping or coin tossing is the practice of throwing a coin in the air to resolve a dispute between two parties or otherwise choose between two alternatives. ...
As real world implementation the objects provided by the extended model are usually established in an special setup phase that follows its own rules, such models are also referred to as models with special setup assumptions.
References - ^ Ran Canetti, Oded Goldreich and Shai Halevi, The Random Oracle Methodology Revisited, STOC 1998, pp209–218 (PS and PDF).
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