Provided is a speech recognition system, including: a first information processing device including a speech recognition processing unit for receiving data to be used for speech recognition transmitted via a network, carrying out speech recognition processing, and returning resultant data; and a second information processing device connected to the first information processing device via the network. The second information processing device performs conversion of the data into data having a format that disables a content thereof from being perceived by application of a mapping function on phoneme ID's associated with the content, and also enables the speech recognition processing unit to perform the speech recognition processing. Thereafter, the second information processing device transmits the data to be used for the speech recognition by the speech recognition processing unit and constructs resultant data returned from the first information processing device into a content of a valid and perceivable recognition result.