Canetti, Hohenberger

Chosen-Ciphertext Secure Proxy Re-Encryption

multi-hop, bidirectional re-encryption through a proxy.
Proxy can translate message from key(1) to key(2) without gaining any 
knowledge about what message contains.

Extension of IBE scheme.

id=X <X,Rx>

Server master secret SR

F(SR,X)=Rx

It is meaningful to reduce the assumption from random oracle.
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