Building a Self-Verifiable Client (SPV) on Ethereum: Step-by-Step

You can run the SPV client as a standalone node to verify and download blocks from the Ethereum network without relying on exchanges or central nodes. This allows for greater control and flexibility in blockchain exploration.

In this article, we will walk you through the steps to build an SPV client and sync it with the Ethereum network.

What is a Self-Verifiable Client (SPV)?

A self-verifiable client (SPV) is a software component that acts as an intermediary between a user’s client and the Ethereum mainnet. Using an SPV client, you can verify the integrity of blocks without relying on a central node.

۱. Step 2: Download the Ethereum Blockchain

Before building an SPV client, make sure you have downloaded the latest blockchain data for the Ethereum network. You can use tools like “geth” or “ethers.js” to download block headers and transaction hashes.

Here is an example of how to create a basic SPV client using “geth”:

Create a new directory for the SPV client
mkdir etc.

Install geth
npm install -g geth

Download the latest data from the Ethereum blockchain
geth downloadblockchain --datadir ./data

۲. Step 2: Configure Bloom Filter

To configure Bloom filters, you need to create a “bloomfilter.json” file in the ./data/ directory. This file stores information about the addresses you want to check.

Create the following files:

{
"addresses": {
"0x1234567890abcdef": true,
"0x234567890abcdef1": false
}
}

This configuration instructs the “bloomfilter.json” file to mark the address “0x1234567890abcdef” as verified.

۳. Step 2: Connect to a peer

To sync with peers, you need to create an SPV client using your preferred node protocol (e.g. JSON-RPC or Websocket). This allows you to connect to multiple nodes and independently verify blocks.

Here is an example of using “ethers.js”:

const ethers = request('ethers');
// Create a new instance of the Ethereum provider
const provider = new ethers.providers.JsonRpcProvider('
// Set the SPV client to the preferred node protocol (e.g. JSON-RPC or Websocket)
const spvClient = new ethers.SpvClient(provider, {
// Set the bloom filter configuration to address 0x1234567890abcdef
bloom-filter: {
addresses: [
'0x1234567890abcdef'
],
value: true
}
});

۴. Step 1: Download all block headers since the last checkpoint

Once the SPV client is configured and connected to a peer, it can start downloading block headers since the last checkpoint.

Here is an example of using “geth”:

Download all block headers since the last checkpoint
geth downloadblockchain --datadir ./data --maxBlockNumber 1000000

Step 5: Re-request all blocks with…

To verify that the SPV client is working correctly, you should re-request each block. This ensures that the client has received all blocks since the last checkpoint.

Here is an example usage of “ethers.js”:

// Download all block headers since the last checkpoint
geth downloadblockchain --datadir ./data --maxBlockNumber 1000000
// Re-request all blocks with...
const geth = new ethers.SpvClient(provider, {
// Set the bloom filter configuration to address 0x1234567890abcdef
bloomfilter: {
addresses: [
'0x1234567890abcdef'
],
value: true
}
});
// Re-download all block headers since the last checkpoint
geth downloadblockchain --datadir ./data --maxBlockNumber 1000001

By following the steps below, you can create a self-verifying client (SPV) on Ethereum and verify the integrity of blocks without relying on central nodes.