An information processing method in an information processing system including a communication apparatus and an information processing apparatus, the communication apparatus including a first communication unit that performs communication via a predetermined wireless communication, the information processing apparatus including a second communication unit that performs communication via the predetermined wireless communication, the information processing method comprising: writing, by the communication apparatus, key information to be used for generating a decryption key, into a storage area of the communication apparatus; reading, by the information processing apparatus, using the second communication unit, first information and the key information that has been written into the storage area; generating, by the information processing apparatus, the decryption key based on the read key information; decrypting, by the information processing apparatus, the read first information using the generated decryption key; performing, by the information processing apparatus, a registration process for registering the communication apparatus if it is determined that the decryption key is generated and if the decrypted first information corresponds with second information which is stored in advance in the information processing apparatus, wherein the registration process is not performed if it is determined that the decrypted first information does not correspond with the second information; performing the communication via the predetermined wireless communication with the information processing apparatus, in a case where the information processing apparatus performs the registration process, and performing, by the communication apparatus, control regarding the key information stored in the storage area such that the key information becomes invalid if an elapsed time from when the key information is written into the storage area in the writing exceeds a predetermined time, wherein the decryption key is not generated if the read key information is invalid, wherein the communication apparatus is configured to write the key information into the storage area if a first event or a second event occurs, and wherein the predetermined time differs between a case where the key information is written in response to occurrence of the first event and a case where the key information is written in response to occurrence of the second event. writing, by the communication apparatus, key information to be used for generating a decryption key, into a storage area of the communication apparatus; reading, by the information processing apparatus, using the second communication unit, first information and the key information that has been written into the storage area; generating, by the information processing apparatus, the decryption key based on the read key information; decrypting, by the information processing apparatus, the read first information using the generated decryption key; performing, by the information processing apparatus, a registration process for registering the communication apparatus if it is determined that the decryption key is generated and if the decrypted first information corresponds with second information which is stored in advance in the information processing apparatus, wherein the registration process is not performed if it is determined that the decrypted first information does not correspond with the second information; performing the communication via the predetermined wireless communication with the information processing apparatus, in a case where the information processing apparatus performs the registration process, and performing, by the communication apparatus, control regarding the key information stored in the storage area such that the key information becomes invalid if an elapsed time from when the key information is written into the storage area in the writing exceeds a predetermined time, wherein the decryption key is not generated if the read key information is invalid, wherein the communication apparatus is configured to write the key information into the storage area if a first event or a second event occurs, and wherein the predetermined time differs between a case where the key information is written in response to occurrence of the first event and a case where the key information is written in response to occurrence of the second event.