The engineer dissolved a public transport card, known as Troika, in acetone to extract the NFC chip. He then covered the chip with silicon and implanted it through an incision in his hand.
Zaytsev programmed the chip to pay for the public transport and unlock doors to the office.
Have a look:
Troika is a reusable card offering an array of fares for public transport in Moscow.
It can also be used to pay for commuter trains and express trains to and from airports serving the Russian capital. Troika cards can be also used to rent bikes in the city center during the summer.
The cards can be bought in any metro ticket office or from vending machines and refilled in ticket offices, online or at mobile phone stores.