CODEWITHSUNDEEP
nfcsmartcardrfidjavacardmifare
Míla Mrvík
Míla Mrvík

Reputation: 535

NFC smartcard that is impossible to clone

First, I want to apologize. I am complete noob in this area and many of my thoughts are probably misleading.

I need to verify that a user of my app is on a specific place in order to be authirized to perform an action. I want to use NFC for this purpose. The user have to put his smartphone by a NFC tag in order to be authorized to perform the action. Easy but I need it to be reasonably hackerproof. It means that the NFC tag must be impossible to clone without physical damage to the plastics around the NFC chip. It also means that the NFC chip must not contain only static data. The NFC chip must contain an app, that can receive some data (cryptographic challenge) and signs them using secure built-in private key (which must be unreadable through NFC interface). When the user wants to perform the action, he will ask server for the challenge, then he lets the chip to sign it, and then he sends the signed challenge back to the server which will verify the signature using known public key. This should be achievable using NFC JavaCard. But do these NFC JavaCards actually exist? I wasn't able to find a company which would be able to produce such NFC tags for me. When I try to explain my requirements to a NFC tags producer he looks like he has never heard of NFC JavaCards. I have tried about 10 producers without luck.

Can a commonly available chip meet my requirements? I mean a chip from the Mifare familly. I suspect that Mifare DESfire might be able to meet my requirements, but I am not sure.

Feel free to respond with an advertisement, because relevant advertisement is exactly what I look for :)

Upvotes: -1

Views: 3214

Answers (3)

guidot
guidot

Reputation: 5333

I try to collect some useful facts:

  • NFC is a very broad term, just finding that on both sides does not ensure interoperability.
  • Any ISO 14443 (one of the NFC flavours) compliant smart card with crypto functionality should be usable. Note, that a card with native OS may be a viable alternative to a JavaCard, since the functionality to sign a random number is pretty standard.
  • Any smart phone sporting a NFC chip can address such a card in principle. Unfortunately this is strongly dependent on the OS of the smart phone, for Android the relevant class to use is IsoDep, which gives you the APDU interface. After triggering the "card enters field" event, then the app receives a handle, via which further communication can take place.
  • Real smart cards can't be cloned, since you are not able to dump them; especially keys can't be read.

Now some things to consider:

  • Your approach looks unusual, which might become a problem. (To have a portable card somehow fixed to a wall, just to get the location; so you know where somebody is, but not who? While I don't consider cloning to be an issue, you somehow must ensure destruction in case of a theft attempt, which may collide with the distance topic below.)

  • I don't see, where the server comes into play. If not involved in the authorized action, provision of a random number is not sufficient reason.

  • Asymmetric key operations have a comparatively high power consumption, and this power has to be supplied via the electric field. This severely limits the distance between card and phone and may even require direct touch. While a power supply of its own would solve the issue in principle, it is not what ISO-14443 was designed for.

Upvotes: 2

Míla Mrvík
Míla Mrvík

Reputation: 535

The answer a was looking for is not a chip which runs a custom code. Although this might be possible it is definitely not the best way to achieve the target.

I was looking for a solution that enables strong authentication using NFC data. There might be multiple chips that offers this, but probably the most available chip is NTAG 424 DNA TT. It works like this:

  1. The chip has a memory, which is not readable through NFC. Private key is stored there.
  2. The chip has a read counter. It increments everytime the data are read through NFC.
  3. The chip can generate an AES-128 signature of string UID (chip serial number) + counter using the private key in the inaccessible part of the memory.
  4. The chip can dynamicaly inject the data above into a URL that is stored in the readable memory.

So the solution will be like (I am waiting for delivery of NFC tags right now, so I don't know for sure yet):

  1. Read the tag UID (serial number) and the actual counter value (should be 0 on an unused tag)
  2. Generate the key-pair
  3. Load private key to the chip
  4. Load some data (URL, eg: https://my.app/) to the chip
  5. Store UID, public-key, last-counter on the server
  6. Configure the chip to inject UID, counter, signature to the URL stored on the chip

When a client reads the data, they should contain required variables, eg: https://my.app/?counter=1&uid=ff:ff:ff:ff&signature=xyz. Then on the server:

  1. Fetch stored info (public-key, last-counter) using uid as a primary key
  2. verifies the signature
  3. verifies the counter that must be > last-counter
  4. stores counter as the last-counter
  5. successfully authorized

Is anyone able to hack this without reading the hidden memory of the chip which would require physical tampering with the chip?

Upvotes: 1

Andrew
Andrew

Reputation: 10222

Yes JavaCards do exist.

https://github.com/OpenJavaCard/openjavacard-ndef is a project makes these JavaCards to output standard NDEF messages (thought note issue 4 in that there example uses the wrong APDU but that is easily changed)

This project also give a number of cards it is fully working and tested for

ACS ACOSJ - fully working
NXP JCOP J3D040/J3D081/J2E145 etc - fully working

Both ACS and Cardlogic do cards (just google the model numbers) e.g.

https://www.acs.com.hk/en/products/405/acosj-java-card-combi/

https://www.smartcardfocus.com/shop/ilp/id~707/j3a081-80k/p/index.shtml

Upvotes: 1

Related Questions