I have the equivalent of an Oyster card (proximity based public transport card).
I'm interested in having the information stored in another way so I don't have to carry around yet another card, perhaps stored on a ring or an NFC enabled smartphone.
Can this be done?
I know there are NFC rings and you can get NFC implantable chips, but can the information be removed from the Oyster card and transferred into the ring, smartphone or implant?
According to Engadget it should be able to work, as the Oyster cards seem to operate by NFC. The article also mentions the ability to use other kinds of cards and other NFC tag based trinkets (NFC sticker, NFC wristband). However, these are all issued by financial institutions, so they would reasonably contain some kind of encryption that might be hard to integrate with off the shelf NFC tags.
If I were you I'd try scanning an Oyster card using an NFC reader application, like this one. If you find that the card returns a fixed value for each reading, then go ahead and try to program this value into a custom NFC tag, essentially copying the card. If this new "card" can be used with the official Oyster readers then you are all set. However, it probably won't work, but there is still hope (see next paragraph).
This video suggests that the Oyster cards use some kind of security chip (Mifare Classic Smartcard Chip). This is reinforced by Wikipedia too. It seems to be possible to buy this kind of chip from this website.
A well-designed contactless card performs cryptography using a secret key when you access information. An NFC reader information only returns public information, not the information that the fare gates verify. A badly-designed card returns a fixed value; these are common in building access but not so much in transportation. In between, you have low-end Mifare cards which use encryption but with algorithms that can be broken.
So the upshot is that it depends on the precise model of transportation card.
In any case, if your transportation authority doesn't offer a way to replicate the card information, then even if you manage to transfer the information to a phone or to an implant, that won't make your phone or implant a valid fare medium and you would likely face fines if inspected.
