A computer-implemented method for sharing information about a subject without disclosing identification information of the subject includes comparing, by a computer system, a third set of data with a fourth set of data. The third set of data is converted by a transformation from a first set of data. The first set of data comprises identification information of a first subject. The fourth set of data is converted by the transformation from a second set of data. The second set of data comprises identification information of a second subject. The transformation renders the first subject unidentifiable from the third set of data and the second subject unidentifiable from the fourth set of data. The computer-implemented method also determines, by the computer system, that the first subject corresponds to the second subject when the third set of data corresponds to the fourth set of data.