Method and system for privacy-preserving social media advertising

An aggregator in an electronic commerce system, the aggregator comprising:

• a network interface configured to receive data via a data network;
• a memory;
• and
• a processor operatively connected to the network interface and the memory, the processor being configured to:
• receive a plurality of ciphertexts and a plurality of signatures transmitted from a plurality of clients with the network interface, each ciphertext in the plurality of ciphertexts including encrypted data corresponding to noisy plaintext data of a category of information for a user that purchased a product, and each signature corresponding to a ciphertext in the plurality of ciphertexts;
• generate a first sum of the plurality of ciphertexts;
• generate a first sum of the plurality of signatures;
• verify the first sum of the plurality of ciphertexts with a homomorphic signature system based on the first sum of the plurality of signatures and homomorphic verification data stored in a memory of the aggregator;
• decrypt the first sum of the plurality of ciphertexts in a private stream aggregation (PSA) process based on homomorphic decryption data stored in the memory of the aggregator to generate a first sum of noisy plaintext data in response to a success of the verification;
• and
• identify aggregate statistical information transmitted from the plurality of clients based on the first sum of noisy plaintext data while preserving differential privacy of the plurality of clients.

A method for operating an aggregator in an electronic commerce system, the method comprising:

• receiving, with a network interface in the aggregator, a plurality of ciphertexts and a plurality of signatures transmitted from a plurality of clients, each ciphertext encrypting noisy plaintext data of a category of information for a user that purchased a product, and each signature corresponding to noisy plaintext data that are encrypted in each ciphertext in the plurality of ciphertexts;
• generating, with a processor in the aggregator, a sum of the plurality of ciphertexts;
• generating, with the processor in the aggregator, a first sum of the plurality of signatures;
• decrypting, with the processor in the aggregator, the sum of the plurality of ciphertexts in a private stream aggregation (PSA) process based on homomorphic decryption data stored in a memory of the aggregator to generate a first sum of noisy plaintext data;
• verifying, with the processor in the aggregator, the first sum of noisy plaintext data with a homomorphic signature system based on the first sum of the plurality of signatures and homomorphic verification data stored in the memory of the aggregator;
• and
• identifying, with the processor in the aggregator, aggregate statistical information transmitted from the plurality of clients based on the first sum of noisy plaintext data while preserving differential privacy of the plurality of clients.