Hyperledger Web3J: Bridging Decentralized Identity & EVM

Notice: Please seek advice from the challenge’s documentation to construct the library to your platform, libdidkit.so on UNIX-like programs, didkit.dll on Home windows, libdidkit.dylib on MacOS.

make -C lib ../goal/launch/libdidkit.so

Add the generated libs from 5 and 6 to the classpath.

Combine Web3J:

If the Java utility was created utilizing Web3J-CLI, the Web3J Gradle plugin is robotically included. If not, you will want so as to add it manually to the construct.gradle file, as described beneath:

plugins {
id(“org.web3j”) model “4.9.8”
}

Notice: SpruceID will run solely on Java 11, on account of this Web3J is specified with model 4.9.8.

Combine with Ethereum check community:

For this we’ll use the Ethereum Sepolia check community to deploy and work together with the good contract ERC-1056. As talked about above, we’ll use Web3J for the deployment and interplay with the good contract. 

First Generate the contract wrapper:

Add the solidity file within the solidity folder underneath the fundamental module.

Run generateContractWrappers gradle activity

Deploy the good contract to the Sepolia check community by executing the tutorial steps right here. Now every thing is in place. 

did:ethr

The did:ethr refers primarily to an Ethereum public handle, which will be resolved to a DID doc utilizing a resolver entity. On this case, SpruceId supplies a resolveDID methodology that can be utilized for this function.

For producing a brand new did:ethr we’ll execute the next code:

//the Sepolia community ID 11155111 in hex
String EVM_CHAIN_ID = 0xaa36a7

public String createEthrIdentity(Machine gadget) throws Exception {
ECKeyPair ecKeyPair = Keys.createEcKeyPair();
String privateKey = Numeric.toHexStringWithPrefix(ecKeyPair.getPrivateKey());
String handle = Numeric.prependHexPrefix(Keys.getAddress(ecKeyPair));
String did = “did:ethr:” + EVM_CHAIN_ID + “:” + handle;
return did;
}

The code above demonstrates how the Keys class from the Web3J utility module is used to generate the SECP-256k1 key pair for the brand new handle. As soon as created, the brand new DID is fashioned by combining the prefix with the brand new key. 

Notice: EVM_CHAIN_ID specifies which community the resolver ought to verify to resolve the DID. 

The ensuing DID ought to have the next format:

did:ethr:0xaa36a7:0x19e03255f667bdfd50a32722df860b1eeaf4d635

If we had generated the DID for Ethereum Mainnet, it will be:

did:ethr:0xaa36a7:0x19e03255f667bdfd50a32722df860b1eeaf4d635

Notice: Bear in mind to retailer the non-public key generated above for later use. You will want it when producing Verifiable credentials. As a greatest apply, encrypt it with an RSA key and retailer it in a personal database till it’s wanted once more.

Test possession

Even when the DID was created off-chain utilizing Hyperledger Web3J, it capabilities on the community like some other SECP-256k1 handle by default. Subsequently, there isn’t a must take any extra steps so as to add it to the Identification Registry. The registry robotically resolves all queries for newly generated did:ethr addresses as a result of they’re already related to their respective homeowners.

public String checkOwner(String did) throws Exception {
Web3j web3j = Web3j.construct(new HttpService(NETWORK_RPC));
FastRawTransactionManager transactionManager = new FastRawTransactionManager(web3j, Credentials.create(id.getKeyUsed()), Numeric.toBigInt(DIDConstants.EVM_CHAIN_ID).longValue());

EthereumDIDRegistry registry = new EthereumDIDRegistry(REGISTRY_ADDRESS, web3j, transactionManager, new DefaultGasProvider());

String identityAddress = did.substring();

return registry.identityOwner(identityAddress).ship();
}

Within the above code, Hyperledger Web3J is querying the registry good contract to retrieve the proprietor of the present DID. 

Notice: the identityAddress is obtained by eradicating the DID prefix (did:ethr:EVM_CHAIN_ID), which represents the beforehand generated public handle. If the proprietor was not beforehand set, the tactic ought to return the saved handle worth as identityAddress by default. Which means each account is the proprietor of its personal DID.

Generate Verifiable Credentials

As soon as the DID is generated and the proprietor’s non-public secret is out there, entry to the Decentralized Identification Area turns into doable. Verifiable Credentials (VCs) function digital representations of bodily IDs within the Web3 area. For additional understanding of their use case, please seek advice from the articles talked about within the introduction part.

To generate VCs, we’ll make the most of SpruceID and Hyperledger Web3J together with the non-public key generated earlier.

public String issueVerifiableCredential(String did, KeyPair keys, DataObject knowledge){

last CredentialObject credential = new CredentialObject(did, did, knowledge);

last DIDKitOptions choices = new DIDKitOptions(PROOF_ASSERTION, id.getVerificationMethod(), null, null);

last String credentialJson = MAPPER.writeValueAsString(credential);
last String optionsJson = MAPPER.writeValueAsString(choices);

String jwk = generatePrivateJwk(keys);

last String verifiableCredential = DIDKit.issueCredential(credentialJson, optionsJson, jwk);
return verifiableCredential;
}

Within the above code, DIDKit is the JNI interface positioned within the jar file that we added to the category path. It exposes the issueCredential methodology which receives the next arguments:

credentialJson = is the physique of the VC. Created from the CredentialObject, it contains the specified knowledge that should conform to the VC schema. Check with the SpruceId instance for steerage.
optionsJson = this refers to the kind of assertions that Verifiable Credential might want to help throughout verification requests;
jwk = is the Json Internet Key format of the did:ethr’s key pair. Methodology generatePrivateJwk ought to include the Web3J code which returns the non-public JWK, documentation right here.

As soon as SpruceID receives the issueCredential request it can begin to do the next:

Test if credentialJson respects the VC schema talked about in @context;

Resolve the did:ethr so as to get the DID Doc to verify the JWK that was despatched. Relying on the check community 2 choices can happen:

If the SpruceId library resolve methodology is suitable with the community, the DID can be resolved.

If the library shouldn’t be suitable, the resolver must be overridden with this customized resolver. 

You possibly can obtain this by cloning the repository and executing the npm command to start out the resolver occasion. After occasion begins, redirect the SpruceId calls by overriding the DIDKit resolve actions to the brand new resolver.

    3. After finishing the primary two steps, the system returns the verifiable credential.

From right here, you need to use it in verification calls, issuing new Verifiable Shows, and extra.

Revoke DID

A DID is revoked when its DID Doc can now not be retrieved. For many DID strategies, this may be achieved by eradicating entry to it. Within the case of did:net, the entry URL to the DID doc is revoked. However what about did:ethrs when there may be an Identification Registry on the community?

On this case, revocation of the DID will consist of adjusting the proprietor handle to 0x0. By doing this, we point out that solely the handle 0x0 can use it. Nonetheless, as 0x0 shouldn’t be a legitimate handle that can be utilized, the DID is successfully revoked.

registry.changeOwner(identityAddress,”0x0″).ship();

Hyperledger Web3J connects Decentralized Identification (DID) programs with Ethereum Digital Machine networks, offering important help for creating decentralized identities. Its interfaces make it simpler to work together with the EVM community and generate essential JWK keys for id creation processes, corresponding to these utilized in Spruce ID.