Speeding Up Sensor Data Encryption with a Common Key Cryptosystem combined with Fully Homomorphic Encryption on Smartphones

Statistical analysis using cloud services to utilize sensor data acquired by IoT devices such as smartphones has become widespread. Highly confidential data, such as location information, exists in sensor data acquired by IoT devices, and it is necessary to protect personal information in case of information leakage on cloud services that are not necessarily safe. Therefore, fully homomorphic encryption that can add and multiply ciphertexts has attracted attention. However, public key cryptosystems are generally slower than common key cryptosystems, and fully homomorphic encryption, which is a public key cryptosystem, takes long processing times. Thus, implementation on IoT devices that have low computational power is an issue. In this research, we propose a combination of common key cryptosystems and fully homomorphic encryption, which is a public key cryptosystem, to perform high-speed encryption and statistical analysis on cloud services even on devices with limited computational resources.