An Algebraic Framework for Diffie–Hellman Assumptions

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• 作者：Alex Escala ; Gottfried Herold ; Eike Kiltz ; Carla Ràfols…
• 关键词：Diffie–Hellman assumption ; Generic hardness ; Groth–Sahai proofs ; Hash proof systems ; Public ; key encryption
• 刊名：Journal of Cryptology
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：30
• 期：1
• 页码：242-288
• 全文大小：
• 刊物类别：Computer Science
• 刊物主题：Coding and Information Theory; Computational Mathematics and Numerical Analysis; Combinatorics; Probability Theory and Stochastic Processes; Communications Engineering, Networks;
• 出版者：Springer US
• ISSN：1432-1378
• 卷排序：30

文摘

We put forward a new algebraic framework to generalize and analyze Diffie–Hellman like decisional assumptions which allows us to argue about security and applications by considering only algebraic properties. Our \(\mathcal {D}_{\ell ,k}\text{- }\textsf {MDDH}\) Assumption states that it is hard to decide whether a vector in \(\mathbb {G}^\ell \) is linearly dependent of the columns of some matrix in \(\mathbb {G}^{\ell \times k}\) sampled according to distribution \(\mathcal {D}_{\ell ,k}\). It covers known assumptions such as \(\textsf {DDH},\, 2\text{- }\textsf {Lin}\) (Linear Assumption) and \(k\text{- }\textsf {Lin}\) (the k-Linear Assumption). Using our algebraic viewpoint, we can relate the generic hardness of our assumptions in m-linear groups to the irreducibility of certain polynomials which describe the output of \(\mathcal {D}_{\ell ,k}\). We use the hardness results to find new distributions for which the \(\mathcal {D}_{\ell ,k}\text{- }\textsf {MDDH}\) Assumption holds generically in m-linear groups. In particular, our new assumptions \(2\text{- }\textsf {SCasc}\) and \(2\text{- }\textsf {ILin}\) are generically hard in bilinear groups and, compared to \(2\text{- }\textsf {Lin}\), have shorter description size, which is a relevant parameter for efficiency in many applications. These results support using our new assumptions as natural replacements for the \(2\text{- }\textsf {Lin}\) assumption which was already used in a large number of applications. To illustrate the conceptual advantages of our algebraic framework, we construct several fundamental primitives based on any \(\textsf {MDDH}\) Assumption. In particular, we can give many instantiations of a primitive in a compact way, including public-key encryption, hash proof systems, pseudo-random functions, and Groth–Sahai NIZK and NIWI proofs. As an independent contribution, we give more efficient NIZK and NIWI proofs for membership in a subgroup of \(\mathbb {G}^\ell \). The results imply very significant efficiency improvements for a large number of schemes.