Secure computing

We study a problem of secure computation by multiple parties of a given function of their cumulative observations, using public communication but without revealing the value of the function to an eavesdropper with access to this communication. A Shannon theoretic formulation is introduced to characterize necessary and sufficient conditions for secure computability. Drawing on innate connections of this formulation to the problem of secret key generation by the same parties using public communication, we show that a function is securely computable if and only if its entropy is smaller than the secret key capacity. Conditions for secure computability at a lone terminal are also derived by association with an appropriate secret key generation problem.