The invention discloses an unbalanced privacy set intersection method suitable for an untrusted cloud. The
client C has a set X = {x1,..., xn}, the
server S has a private set Y = {y1,..., yN}, and the untrusted
cloud server H has no input, nlt; lt; the method comprises the following steps: (1) initializing a
system; and (2) data blinding. And (3)
data outsourcing. And (4) the untrusted cloud and the
server side carry out interactive calculation. And (5) calculating an intersection. According to the method, firstly, an efficient casual privacy equivalence
test protocol is designed; by encoding the set elements and combining with the casual transmission extension protocol, the
cloud server and the
service provider can carry out equality test on the set elements in a secrecy manner. And secondly, blind
processing is carried out on the private set, and the main calculation task of the
client C is outsourced to the untrusted cloud H, so that the calculation burden of the
client C is reduced. And finally, by introducing a Pedersen commitment and a zero-knowledge proof mechanism, possible malicious behaviors of the untrusted cloud H can be resisted, and the security of the
system is enhanced.