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SUMMARY:Smooth Projective Hashing for Conditionally Extractable Commitment
 s
DTSTART:20090618T100000
DTSTAMP:20260407T105359Z
UID:783b1872d09ad072c57b850f56c8e5db19abbe3735e594537a304c44
CATEGORIES:Conferences - Seminars
DESCRIPTION:David Pointcheval\nThe notion of smooth projective hash functi
 ons was proposed by\nCramer and Shoup and can be seen as special type of z
 ero-knowledgeproof\nsystem for a language. Though originally used as a mea
 ns to build\nefficient chosen-ciphertext secure public-key encryption sche
 mes\, some\nvariations of the Cramer-Shoup smooth projective hash function
 s also\nfound applications in several other contexts\, such as password-ba
 sed\nauthenticated key exchange and oblivious transfer.\nIn this talk\, we
  first address the problem of building smooth projective\nhash functions f
 or more complex languages. More\nprecisely\, we show how to build such fun
 ctions for languages that can be\ndescribed in terms of disjunctions and c
 onjunctions of simpler languages\nfor which smooth projective hash functio
 ns are known to exist.\nNext\, we illustrate how the use of smooth project
 ive hash functions with\nmore complex languages can be efficiently\nassoci
 ated to extractable commitment schemes and avoid the need for\nzero-knowle
 dge proofs. Finally\, we explain how to apply these results to\nprovide mo
 re efficient solutions to two well-known cryptographic\nproblems: a public
 -key certification which guarantees the knowledge of\nthe private key by t
 he user without random oracles or zero-knowledge\nproofs and adaptive secu
 rity for password-based authenticated key\nexchange protocols in the unive
 rsal composability framework with erasures.\n\nThis is a joint work with M
 ichel Abdalla and Céline Chevalier.
LOCATION:INF 2.11
STATUS:CONFIRMED
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