Design an NFC/DID based identity system

[truedat101]

The project needs a way to represent identities with an NFC tag and using concepts defined in https://w3c.github.io/did-core/

Start prototyping an architecture here.

[truedat101]

@Damfortx8 can you start looking into how we might utilize NFC for the DID identity.

Concept: A user ID is tied to the NFC card and phone. I'm thinking we could store the secret key, encrypted in the NFC tag. It would be the job of the phone to prompt the user with a password, and decrypt the key, and then use the key data to sign transactions, etc.

I've reviewed the information here :https://docs.substrate.io/tutorials/v3/private-network/ to try to understand this a bit better.

[truedat101]

@Damfortx8 the other concept I'd like to be able to perform is assign the identifier for a product into the NFC tag, and be able to scan the tag and load the verification of the entire "chain of custody" . In theory, this could simply open the web page of the view that shows the entire set of steps of creating this bag of coffee beans.

[truedat101]

One issue I have had is getting the initial concept for how to use the NFC tags nailed down. I've been looking for some existing open source examples of NFC/blockchain utilization. In principle, the tag needs to store a private key in a secure element, and we'd use the app on a phone to unlock the tag and in theory, sign transactions.

[truedat101]

I found a few projects as reference points:

• A bitcoin wallet project https://github.com/720kb/BitNFC/blob/master/www/js/providers/nfc.js#L13 + NFC API (thoughts and info) 720kb/BitNFC#24
• UDID approach: https://github.com/leukaemiamedtech/HIAS-NFC-Reader ... this is good for using the wallet as an identifier for a "person" or object
• Ledger javacard https://github.com/LedgerHQ/ledger-javacard (defunct project)

[truedat101]

There really isn't much published. That's a surprise.

[truedat101]

Some details on the substrate/polkadot key/accounts:

• it uses sr25519
• Detailed spec https://wiki.polkadot.network/docs/learn-keys
• software in rust https://docs.rs/schnorrkel/0.9.1/src/schnorrkel/keys.rs.html#43
• private key size: secret key size (32) + nonce size (32) = 64
• public key size: 32
• keypair size = private key size plus public key size (96)

Regarding our NFC tags we most definitely can fit them into memory! The ST25 tags that I have I think are mostly 256 bytes of data available. That means we can, in theory store a key pair. Yes!

[truedat101]

I've verified there is a way to lock entire areas of the ST25 cards, password protect for read/write. User has to set up a pin sort of thing. While I can use this, maybe we just want to leave it insecure for a demo. Seems like something I can add later. TBD.