Secure-fragment-conversion methods and apparatuses for protecting privacy data

Abstract

In an implementation, a first party or a third party updates, by adding an offset to the first fragment, two local fragments held by the local party, where the offset enables offset data obtained by performing addition on updated fragments of each party to be greater than or equal to 0. Multi-party joint computation is performed by using the two updated local fragments together with fragments held by the other two parties to obtain two overflow fragments of an overflow bit and in a second ring for performing a modulo operation on a second value of an n power of 2, m is less than n; and the overflow bit indicates whether the offset data is greater than or equal to the first value. Two converted fragments are obtained in the second ring based on the two updated local fragments, the two overflow fragments, and the offset.