八達通
The Octopus card uses encryption for all airborne communication and performs mutual authentication between the card and reader based on the ISO 9798-2 three-pass mutual authentication protocol. In other words, data communications are only established when the card and reader have mutually authenticated based on a shared secret access key. This means that the security of the Octopus card system would be jeopardized should the access key be exposed. A stolen Octopus card reader could be used with stolen Octopus software, for example, to add value (up to HK$3,000) to any Octopus card without authorization. Nevertheless, as of 2003, the Octopus card and system had never been hacked.