This article describes the operating system Calypso which provided the basis for new public transport ticketing in Paris, France. Calypso used GSM mobile telephony standards to design and specify a secure card-to-terminal interface. An independent consultant was chosen to develop the required specifications, test them and make them accessible to suppliers. Card security was seen as a highly important element and ensures data protection while allowing easy access to the transport system. Other criteria involved in the development of Calypso include speed of use, ease of use, versatility, interoperability, multiple applications, and compatibility. The operators set up a not-for-profit organisation, the Calypso Networks Association, to handle short-term interoperability requirements, long-term vision for future needs, and evolution of standards. Three working groups have been set up for interoperability, specification and technical development, and promotion and standardisation.
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