Patent ID: 7657028

Claim:
A method for securely classifying private data of a first party using a classifier H(x) of a second party, comprising a client and a server for performing steps of the method, comprising the steps of: (1) providing, using the client, private data of a first party as a vector x, and providing, using the server, a classifier H ⁡ ( x ) = sign ⁡ ( ∑ n = 1 N ⁢ h n ⁡ ( x ) ) by a second party, where h n ⁡ ( x ) = { α n x T ⁢ y n > Θ n β n otherwise ; α n , β n and Θ n are scalar values; and y n is a vector storing parameters of the classifier, and generating, by the second party, a set of N random numbers, s 1 , . . . , s N , such that s = ∑ n = 1 N ⁢ s n ; (2) performing, for each n=1, . . . , N, the sub-steps: (a) applying a secure dot product to x T y n to obtain a n for the first party and b n for the second party; (b) applying a secure millionaire protocol to determine whether a n is larger than Θ n −b n , and returning a result of a n +s n or β n +s n ; (c) accumulating, by the first party, the result in c n ; and (3) applying the secure millionaire protocol to determine whether c = ∑ n = 1 N ⁢ c n is larger than s = ∑ n = 1 N ⁢ s n , and returning a positive sign if true, and a negative sign if false to classify the private data x, wherein the providing, the performing, and the applying steps are performed in part by the client and in part by the server using secure multi-party protocols.