Sidetree-Cardano

Sidetree-Cardano is an implementation of Sidetree protocol on top of Cardano Blockchain and IPFS. It is based on the reference framework provided by the Decentralized Identity Foundation (DIF).

Sidetree-Cardano nodes provide a public, permissionless, Decentralized Identifier (DID) Layer 2 network that support scalable DIDs/DPKI operations.

This development is part of my proposal Interoperability as Growth Driver submitted to Project Catalyst Fund 6 that finally got funded. Thanks for voting!!! See the list of my new proposals for Fund 7.

Take note that this project is in Beta phase and improving is underway. Testing and collaboration are welcomed!

Install & Run

1. Install and run mongodb
2. Install and run IPFS
3. Clone the repo git clone git@github.com:rodolfomiranda/sidetree-cardano.git
4. Install required packages npm install
5. Configure wallet mnemonic (with funds) in json config files
6. Build yarn build
7. Run yarn start

Try out some DID operations

Sidetree-Cardano exposes a REST API at http://localhost:3000 that receives DID operations, and there's also a swagger UI deployed at http://localhost:8080 (you can remove it from start script if you won't use it). However, if you don't want to build and run the node, you can use a testnet node located at https://testnet.sidetree-cardano.com.

Either way, and in order to facilitate and ilustrate DID operations, you'll find several snippets in the folder examples that you can run to create, update, recover, deactivate and resolve DIDs. In the examples we use the handy ion-sdk to generate the body of the operations. See the walk-in guide here.

TODO's

• Improve error handling
• Implement spending monitor (control wallet balance and spending rate limits)
• Implement versioning manager
• Add unit tests

Sidetree-Cardano's conventions

Sidetree transactions anchored in Cardano blockchain follow these rules:

1. Sidetree transactions are stored in Cardano blockchain as transaction metadata.
2. It uses a specific metadata top-level key to simplify the queries within the blockchain. We arbitrarily selected the key 74338733 ('sidetree' in T9 encoding).
3. DID method: did:ada
4. Sidetree specification requires to assign a Transaction Number to each sidetree transaction stored in the ledger, that must be a monotonically increasing number deterministically ordered. For the Transaction Number we use the block number and the index of the transaction in the block in the same way it is used in bitcoin sidetree implementation transactionNumber = blockNumber * (2 ** 32) + txIndex.
5. The metadata stored in Cardano is a string attacched to the top-level key defined above. The string follows the format "sidetree:"+{anchor string as defined in sidetree protocol}
6. A complete sidetree transaction is composed as follows:

{
    "transactionNumber": as described in above
    "transactionTime": block number
    "transactionTimeHash": the hash of the block
    "anchorString": as defined in sidetree protocol
    "transactionFeePaid": Fees of transaction in Lovelaces
    "normalizedTransactionFee": not used (null)
    "writer": wallet address of sidetree-cardano node
}

7. Metadata transaction: it use the first derived Shelley address from mnemonics to transfer 1 ADA to itself and write metadata. The only cost is the tranasction fee that is around 0.17 - 0.18 ADA.
8. Interaction with Cardano blockchain is provided by Gimbalabs Dandelion API or by Blockfrost. You need to select correct import in src/CardanoClient.ts (if you use Bockfrost also need to configure your projectId in json/testnet-cardano-config.json)
9. The protocol waits for a minumun block confirmations until we accepts the transactions as valid. The greated the safer, but it takes longer to have the DID published in blockchain and able to be resolved.
10. Proof of fee and Value Locking were not implememted.

DIF Specifications

• See the latest spec for the full Sidetree specification.
• See the API spec for the full API specification to interact with a Sidetree node.

Sidetree-Cardano vs Atala PRISM

Sidetree-Cardano protocol	Atala PRISM protocol
available now	not avaliable yet. Only for Atala Prism Pioneer Program
open source	will be open source, but not timeframe given
fully complies with W3C DID Document V1 specs	does not comply with W3C DID specs yet. Only stores master, issuing and revocation keys
does not deal with verifiable credentials	verifiable credential hashes are stored in ledger allowing revocations
protocol reliability confirmed in ion(bitcoin) and element(ethereum) implementations	newer protocol, need testing
available in many open source frameworks	open source tools and framework will be developed by the community

Bugs, questions, ideas

Please, open a github issue in this repo.