Base L2 Testnet Anchor Walkthrough

This guide walks through anchoring an Attestix identity or credential to Base L2 testnet (Sepolia). Mainnet schema registration is planned for a future release; testnet is the default target today.

Why anchor?

An Attestix artefact (identity, credential, audit batch) is already Ed25519-signed and hash-chained. Anchoring commits the hash to a public ledger so any third party can:

• Confirm the artefact existed at a specific block height.
• Detect silent mutation of the local store.
• Link an Attestix issuer DID to an on-chain provenance record.

Anchoring is optional. Attestix works fully offline without it.

Prerequisites

pip install attestix

You will need:

1. A Base Sepolia RPC endpoint.
2. A funded wallet on Base Sepolia (0.001 ETH is plenty, free from public faucets).
3. The EAS schema UID for Attestix. This ships with the package.

Step 1 / Configure the testnet RPC

export BASE_RPC_URL=https://sepolia.base.org
export EVM_PRIVATE_KEY=0xyour_private_key_hex_here

Or via .env:

BASE_RPC_URL=https://sepolia.base.org
EVM_PRIVATE_KEY=0x0000000000000000000000000000000000000000000000000000000000000000

EVM_PRIVATE_KEY is the full hex private key with the 0x prefix. Treat it as a secret. Never commit it. Never share it. Use a dedicated test wallet for testnet work; do not reuse mainnet keys.

Step 2 / Fund the wallet

Use any Base Sepolia faucet. Recommended:

• Coinbase Developer Platform faucet for Base Sepolia: https://portal.cdp.coinbase.com/products/faucet
• Alchemy Base Sepolia faucet: https://www.alchemy.com/faucets/base-sepolia

Send around 0.001 ETH to the address derived from EVM_PRIVATE_KEY.

Check balance via the Attestix CLI:

attestix blockchain balance

Or programmatically in Python:

from services.blockchain_service import BlockchainService

svc = BlockchainService()
print(svc.balance())  # e.g. 0.0012 ETH on Base Sepolia

Step 3 / Estimate cost

svc.estimate_anchor_cost(artifact_id="attestix:f9bdb7a94ccb40f1")

Typical numbers on Base Sepolia:

Step 4 / Anchor an identity

tx_hash = svc.anchor_identity(agent_id="attestix:f9bdb7a94ccb40f1")
print(tx_hash)  # -> 0x8f2e4c9b...

Step 5 / Anchor a credential

tx_hash = svc.anchor_credential(credential_id="urn:uuid:9e2f7a3c-...")

Step 6 / Anchor a batch

Merkle-batch 100 artefacts into a single on-chain write:

tx_hash = svc.anchor_audit_batch(
    artifact_ids=[...],  # up to 10,000 per batch
)

Gas cost stays ~48k regardless of batch size. The proof size grows as O(log n) per artefact.

Step 7 / Verify an anchor

status = svc.verify_anchor(artifact_id="attestix:f9bdb7a94ccb40f1")
# -> { "confirmed": True, "block": 23047881, "tx": "0x8f2e...", "schema": "AttestixAgentIdentityV1" }

Run this on a different machine to prove the local store has not been tampered with.

Step 8 / Inspect on a block explorer

Paste the tx hash into Base Sepolia block explorer. You will see:

• The EAS attestation call
• The Attestix schema reference
• The artefact hash as a bytes32 field

Anyone can run the same verification without contacting Attestix or VibeTensor.

Troubleshooting

Error: BASE_RPC_URL not set

See configuration for all environment variables.

Error: insufficient funds

Top up the wallet at a Base Sepolia faucet.

Error: schema UID mismatch

Upgrade to the latest Attestix package: pip install --upgrade attestix.

Mainnet status

Mainnet schema registration is on the roadmap. Once the mainnet schema is registered and validated, BASE_RPC_URL can be pointed at https://mainnet.base.org and the same flow applies with real gas cost. Until then, use testnet.