Patent ID: 8555400

Claim:
A method for sharing sensitive data with a data aggregator, the method comprising: determining a private key for a local user in a set of users, wherein the sum of the private keys associated with the set of users and the data aggregator is equal to zero; selecting, at a client computer, a set of data values associated with the local user; encrypting individual data values in the set based in part on the private key to produce a set of encrypted data values, thereby allowing the data aggregator to decrypt an aggregate value across the set of users without decrypting individual data values associated with the set of users, and without interacting with the set of users while decrypting the aggregate value; and sending the set of encrypted data values to the data aggregator; wherein the set of data values includes a time series, wherein the private key is determined prior to encrypting the individual data values in the time series, wherein the aggregate value includes a summation of the individual values associated with the set of users; and wherein encrypting an individual data value x i,t for a user i and time period t involves computing an expression: c i,t =g x i,t ·H ( t ) sk i wherein c i,t is an encrypted value associated with user i and time period t, wherein g is a generator, wherein sk i is a private key associated with user i, and wherein H(t) is a hash function.