Methods for protecting privacy

A method, comprising:

• at each of a plurality of client devices:
• receiving a data item;
• receiving a public key from a second computing system;
• encrypting the data item using the public key to produce a singly encrypted data item;
• engaging in an oblivious pseudorandom function protocol with a first computing system using the singly encrypted data item to produce a seed;
• generating, using the seed and the singly encrypted data item, an encrypted secret share using a threshold secret sharing function under which the encrypted secret share cannot be decrypted until a threshold number of encrypted secret shares associated with the same singly encrypted data item are received;
• and
• transmitting the encrypted secret share to the first computing system;
• at the first computing system:
• receiving a plurality of encrypted secret shares from the plurality of client devices;
• processing the plurality of encrypted secret shares to produce processed data;
• and
• transmitting the processed data to a second computing system;
• and
• at the second computing system:
• decrypting the processed data to produce decrypted processed data;
• and
• generating, using the decrypted processed data, a count of the plurality secret shares sharing a first characteristic without accessing personally identifiable information associated with the plurality of client devices.