Signer Demo

This repository demonstrates how to use Alchemy's Java Signer SDK to authenticate users and sign real transactions on the Ethereum Sepolia test network.

Maven Dependency

<dependency>
    <groupId>com.alchemy.accountkit</groupId>
    <artifactId>signer-sdk</artifactId>
    <version>0.1.0-alpha-7880b179</version>
</dependency>

Setup

1. Create an Alchemy application
   Go to the Alchemy dashboard and create a new application with both Account Kit and Node API enabled.

2. Insert your API key
   In DemoApplication, replace every instance of "<REPLACE_WITH_API_KEY>" with the API key obtained from Step 1.

3. Onboard your OIDC connector
   Contact the Alchemy team to register (onboard) your OIDC connector.

4. Update OIDC configuration
   In DemoApplication, replace every //CHANGE-ME placeholder with the relevant OIDC setup. Ensure that you can obtain a valid JWT token from your OIDC connector, and note that the JWT’s nonce must be sha256(tekManager.publicKey()).

5. Start the project
   See Start the project below.

Start the Project

mvn spring-boot:run

Deep Dive

DemoApplication defines two primary endpoints: /user and /sign. Both are GET endpoints.

Testing the Endpoints

You can test the endpoints using tools such as curl or Postman.

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The /user Endpoint

When you call /user (with no parameters), the demo:

1. Generates a TekManager object for each end user.
2. Requests a JWT from your OIDC provider.
3. Authenticates with Alchemy using signerClient.authenticateWithJWT.
4. Returns a stamper that can be used to stamp data and exchange it for a real signature.

Example Request (curl):

curl -X GET "http://localhost:8888/user"

Example Response:

{
  "credentialBundle": {
    "bundlePrivateKey": "MEECAQAwEwYHKoZIzj0CAQYIKoZIzj0DAQcEJzAlAgEBBCBaTF44aNZtZsBv/hBFjp9eNeRREOf05hyaOMoqtLRArA==",
    "bundlePublicKey": "A5Kc3SmkRr8Idoyf/mqSL97MKsXR5j0E4pmwsrcgb1oH"
  },
  "user": {
    "email": null,
    "userId": "dfc453cc-df55-4716-8a15-61492b4f0fcc",
    "orgId": "e34032d8-d42f-4980-9f07-b7b40f765789",
    "address": "0x7f9689C78B86B289531f4dA0abf686e55F20A744",
    "solanaAddress": "7YnJFzxkkEiRMxdRSz4cd4FUCidKQv2JfgD6QaGpCLhH"
  }
}

Important:
Before you call /sign, make sure you fund the returned address with some test ETH. You can use the Alchemy Sepolia faucet.

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The /sign Endpoint

Use /sign to sign and broadcast an Ethereum (Sepolia) transaction for the user you retrieved in /user.

Query Parameter:

• userId: The userId from the /user endpoint’s response.

What Happens:

1. The application creates a sample Eth-Sepolia transaction.
2. Calls signerClient.signEthTx using the stamper from /user to sign the transaction.
3. Broadcasts the transaction to the Sepolia test network.

Example Request (curl):

curl -X GET "http://localhost:8888/sign?userId=dfc453cc-df55-4716-8a15-61492b4f0fcc"

Example Response (Transaction Hash):

0x9ef79e1711c6f08a625bc03dc7766f30c75069dc3ce2b18db6f860ed80b4d3a9

You can track the transaction status on Sepolia Etherscan by appending your returned hash to the Etherscan URL, for example:

https://sepolia.etherscan.io/tx/0x9ef79e1711c6f08a625bc03dc7766f30c75069dc3ce2b18db6f860ed80b4d3a9

A sample transaction screenshot:

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Questions or Issues?
If you run into any problems or need help, please contact the Alchemy team or open an issue on this repository.