the key after completing their ablutions. Key fobs offering added functionalities connected to online services may require additional subscription payment to access them. Access control key fobs Access control key fobs are electronic key fobs that are used for controlling access to buildings or vehicles. They are used for activating such things as remote keyless entry systems on motor vehicles. Early electric key fobs operated using infrared and required a clear line-of-sight to function. These could be copied using a programmable remote control. More recent models use challenge–response authentication over radio frequency, so these are harder to copy and do not need line-of-sight to operate. Programming these remotes sometimes requires the automotive dealership to connect a diagnostic tool, but many of them can be self-programmed by following a sequence of steps in the vehicle and usually requires at least one working key. Key fobs are used in apartment buildings and condominium buildings for controlling access to common areas (for example, lobby doors, storage areas, fitness room, pool). These usually contain a passive RFID tag. The fob operates in much the same manner as a proximity card to communicate (via a reader pad) with a central server for the building, which can be programmed to allow access only to those areas in which the tenant or owner is permitted to access, or only within certain time frames. Remote workers may also use a security token – an electronic device often referred to as a fob – that provides one part of a three-way match to log in over an unsecure computer network connection to a secure network. (A well-known example is the RSA SecurID token.) This kind of key fob may have a keypad on which the user must enter a PIN to retrieve an access code, or it could be a display-only device. RFID key fobs can be easily cloned with tools like the Proxmark3, and there are several companies in America that offer this service. Costs The cost of keychains in the United States varies widely depending on their purpose. Advertising keychains begin at only a few cents a piece to a few dollars each. They are normally purchased in large quantities, often over 500 at a time. Keychains are found in retail stores to represent things such as television shows, movies, video games, nostalgia, hobbies, interests, and personalities. These keychains cost from US$1 up to US$10 and more.