Patent ID: 8898478

Claim:
A method for privacy-preserving querying of a set of encrypted data instances located at a server with a query attribute of a client, wherein the set of encrypted data instances is associated with a set of ciphertexts, wherein a ciphertext is an encrypted function of a representation of a corresponding data instance and a data instance attribute extracted from the corresponding data instance, comprising: decrypting the ciphertext from the set of ciphertexts based on a distance function of the query attribute and the data instance attribute to produce the representation, wherein the ciphertext is C ⁡ ( x ( j ) , L j , W ) = ( A 0 , { A i } i = 1 n , A _ , B , H j ) , ⁢ wherein A 0 = ( g q ⁢ c ) γ , ⁢ A i = ( g q ⁢ c ) γ ⁢ ⁢ x i ( j ) ⁢ s i , ⁢ A _ = s 0 ⁡ ( g q ⁢ c ) γ ⁢ ∑ i = 1 n ⁢ ⁢ ( x i ( j ) ) 2 , B=g p δ , H j =L j ·e(g p , α) δ , wherein p, q, r are primes of cyclic groups G and G T of order N=pqr, G p , G q and G r are cyclic groups with orders p, q and r respectively with generators g p , g q and g r respectively, e:G×G→G T is a non-degenerate bilinear map, a belongs to G p and c belongs to G r are randomly chosen parameters, W=(N, g p , g r , g q c, e(g p , α)), and the ciphertext is encrypted with a private master key (p, q, r, g q , α, c); and accessing the corresponding data instance using the representation, wherein steps of the method are performed by a processor of the client.