Offer more efficient hash functions in ABE schemes

[rheitjoh]

(This issue has been imported from the Gitlab repository because it seems to not have been addressed yet)

Original Text (Issue 56)

Many ABE constructions use the Waters Hash function to obtain security in the standard model. The Waters Hash function requires multi-exponentiation in G1 or G2 and is potentially expensive. This issue proposes to make the Hash function interchangeable in the schemes, thus enabling efficient construction in the RO model.

This issue is related to issue 52 because the proposal is to model Waters Hash function as one possible implementation of the interface HashIntoStructure.

Comment by Peter Günther

I implemented Waters Hash function as one possible implementation of HashIntoStrcuture (see also commit https://git.cs.uni-paderborn.de/ag-bloemer/sis/-/commit/63189866e5b28ff4fd69e0ecdc71526c7dc85705). Then, different hash functions can be instantiated. I guess it should be possible to give a generic proof that a scheme S that is secure with Waters hash function in the standard model is also secure in the RO model. Hence, in the RO model that models the complete Hash function into G1 or G2 the schemes should be secure.