Trapdoors for Hard Lattices and New Cryptographic Constructions


Gentry, C., Peikert, C., & Vaikuntanathan, V. (2008, May). Trapdoors for hard lattices and new cryptographic constructions. In Proceedings of the fortieth annual ACM symposium on Theory of computing (pp. 197-206).


We show how to construct a variety of “trapdoor” cryptographic tools assuming the worst-case hardness of standard lattice problems (such as approximating the length of the shortest nonzero vector to within certain polynomial factors). Our contributions include a new notion of trapdoor function with preimage sampling, simple and efficient “hash-and-sign” digital signature schemes, and identity-based encryption. A core technical component of our constructions is an efficient algorithm that, given a basis of an arbitrary lattice, samples lattice points from a discrete Gaussian probability distribution whose standard deviation is essentially the length of the longest Gram-Schmidt vector of the basis. A crucial security property is that the output distribution of the algorithm is oblivious to the particular geometry of the given basis.

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