New result in predicate encryption: disjunction support

[Jonathan Katz]

On Sun, 4 May 2008, Scott Guthery wrote:

> One useful application of the Katz/Sahai/Waters work is a counter to traffic
> analysis.  One can send the same message to everyone but ensure that only a
> defined subset can read the message by proper key management.  What is less
> clear is how to ensure that decrytion with the wrong key doesn't yield an
> understandable (and actionable) message.

This is actually pretty easy to do by, e.g., padding all valid messages 
with sufficiently-many 0s. Decryption with an incorrect key will result in 
something "random" that is unlikely to end with the requisite number of 0s 
(and so will be discarded).

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