A method and system for generating contexts of targets to estimate a high-order context. The system includes: a detection device including: a sensor for detecting a target; module for extracting the target and a primary context of the target based on data detected by the sensor; and module for encrypting the primary context with a key corresponding to the target; a storage device for recording encrypted primary context from the detection device; and a processing device including: module for receiving the encrypted primary context from the storage device; module for receiving the key corresponding to the target involved in the encrypted primary context; module for decrypting the encrypted primary context using received key; and module for estimating a high-order context using the decrypted primary context; where the processing device further includes a module for requesting the detection device to delete information on a key corresponding to a specific target.