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The noisy-storage model refers to a cryptographic model employed in quantum cryptography. It assumes that the quantum memory device of an attacker (adversary) trying to break the protocol is imperfect (noisy). The main goal of this model is to enable the secure implementation of two-party cryptographic primitives, such as bit commitment, oblivious transfer and secure identification. ==Motivation== Quantum communication has proven to be extremely useful when it comes to distributing encryption keys. It allows two distant parties Alice and Bob to expand a small initial secret key into an arbitrarily long secret key by sending qubits (quantum bits) to each other. Most importantly, it can be shown that any eavesdropper trying to listen into their communication cannot intercept any information about the long key. This is known as quantum key distribution (QKD). Yet, it has been shown that even quantum communication does not allow the secure implementation of many other two-party cryptographic tasks.〔 〕〔 〕〔 〕〔 〕 These all form instances of secure function evaluation. An example is oblivious transfer. What sets these tasks apart from key distribution is that they aim to solve problems between two parties, Alice and Bob, who do ''not'' trust each other. That is, there is no outside party like an eavesdropper, only Alice and Bob. Intuitively, it is this lack of trust that makes the problem hard. Unlike in quantum key distribution, Alice and Bob cannot collaborate to try and detect any eavesdropping activity. Instead, each party has to fend for himself. Since tasks like secure identification are of practical interest, one is willing to make assumptions on how powerful the adversary can be. Security then holds as long as these assumptions are satisfied. In classical cryptography, i.e., without the use of quantum tools, most of these are computational assumptions. Such assumptions consists of two parts. First, one assumes that a particular problem is difficult to solve. For example, one might assume that it is hard to factor a large integer into its prime factors (e.g. 15=5x3). Second, one assumes that the adversary has a limited amount of computing power, namely less than what is (thought to be) required to solve the chosen problem. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Noisy-storage model」の詳細全文を読む スポンサード リンク
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