Smooth Projective Hashing for Conditionally Extractable Commitments
Event details
| Date | 18.06.2009 |
| Hour | 10:00 |
| Speaker | David Pointcheval |
| Location |
INF 2.11
|
| Category | Conferences - Seminars |
The notion of smooth projective hash functions was proposed by
Cramer and Shoup and can be seen as special type of zero-knowledgeproof
system for a language. Though originally used as a means to build
efficient chosen-ciphertext secure public-key encryption schemes, some
variations of the Cramer-Shoup smooth projective hash functions also
found applications in several other contexts, such as password-based
authenticated key exchange and oblivious transfer.
In this talk, we first address the problem of building smooth projective
hash functions for more complex languages. More
precisely, we show how to build such functions for languages that can be
described in terms of disjunctions and conjunctions of simpler languages
for which smooth projective hash functions are known to exist.
Next, we illustrate how the use of smooth projective hash functions with
more complex languages can be efficiently
associated to extractable commitment schemes and avoid the need for
zero-knowledge proofs. Finally, we explain how to apply these results to
provide more efficient solutions to two well-known cryptographic
problems: a public-key certification which guarantees the knowledge of
the private key by the user without random oracles or zero-knowledge
proofs and adaptive security for password-based authenticated key
exchange protocols in the universal composability framework with erasures.
This is a joint work with Michel Abdalla and Céline Chevalier.
Practical information
- General public
- Free