Scientists have found a way to circumvent the encryption used to protect a smartcard used to restrict access to buildings and to process public transit system payments. The new hack is carried out using a side channel attack, which bypasses the defensive features intended to prevent attacks on the card. The same team broke a previous version of contactless-ID cards from Mifare in 2008. This prompted the card to upgrade its security to create a card able to be programmed only once and which contained a unique identifying number.
Source: https://thehackernews.com/2011/10/german-researchers-break-rfid-smartcard.html