This way they were able to be offered to a sector that wasn't catered by traditional forms of electronic payment. All value circulated between Mondex cards was issued by an 'originator' - in order to create Mondex value the originator (a part of the local Mondex franchise) would exchange cash with the Mondex partnering banks and provide them with an equal amount of Mondex electronic value, which could be later withdrawn by cardholders using the bank accounts associated to their cards. Transfers, card top-up and payments Mondex is an open-loop implementation of the electronic cash scheme - instead of transactions occurring only in one way, money can be transferred between any Mondex user. A transfer of funds using the Mondex card (dubbed an 'electronic purse') operated through a Mondex-enabled device, and in principle occurred between 2 cards - whether it was 2 customers or a customer and a seller. Both would insert their cards into a device which would facilitate the transfer of funds and record the transaction onto the card. The card's memory consisted of the last 10 transactions. In order to top-up their cards, users could use an ATM, go to a bank branch, or visit several stores and businesses with compatible hardware. Mondex cards that were issued by banks allowed cardholders to transfer funds to and from their personal bank account, which was linked directly to their card. Mondex cards could be used in any store or machine that supported it and had the necessary equipment. Depending on the country where the system was implemented, Mondex cards were accepted at a variety of businesses - supermarkets, department stores, public transport, taxis, car parks, vending machines, restaurants, cafés and many more. Some countries even allowed usage of the cards in lottery games. International use Mondex cards carried five 'electronic pockets', separate from one another, each containing money denominated in a different currency. This allowed transactions to be made using one of the 5 currencies loaded on the card. The currencies in the 'pockets' could be unloaded and replaced at any time. Security features Mondex cards included a locking mechanism - a PIN number would be chosen and inserted to lock the card, and before operating the card again (to view the latest transactions or transfer funds) the cardholder had to insert his PIN number and unlock it. The Z notation was used to prove security properties about Mondex,