Homomorphic encryption schemes allow for very simple "computations" on encrypted data, and are therefore convenient tools in the design of conceptually simple cryptographic protocols. Non-malleability is a property of encryption schemes that is necessary when making security guarantees against active adversaries. However, these two desirable properties of encryption are mutually exclusive.
In this talk, I will discuss how these two opposing demands can be reconciled into a powerful notion for public-key encryption. An interesting application of these new results is an anonymous "opinion polling" protocol, which is efficient and conceptually simple, yet secure in a very strong sense. I will also discuss some relevant consequences regarding symbolic analysis of cryptographic protocols.
This is joint work with Manoj Prabhakaran.