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Version: 3.9

Getting Started with ScalarDL Auditor

This document explains how to get started with ScalarDL Auditor. Here, we assume that you have already finished reading the following guides and gained some experience in overall ScalarDL.

What is ScalarDL Auditor?

ScalarDL Auditor is a component that manages the identical states of Ledger to help clients to detect Byzantine faults. Using Auditor brings great benefit from the security perspective but it comes with extra processing costs, so please think carefully if you really need it.

To make Byzantine fault detection with auditing work properly, Ledger and Auditor should be deployed and managed in different administrative domains. However, for this getting started guide, we assume they are placed in the same network and managed in the same administrative domain.


In this guide, we assume Ledger and Auditor both use Cassandra through ScalarDB, both Cassandra instances use default username and password for the admin privilege. Also, Ledger, Auditor, and Cassandra are all located in the same network so that they can access each other.

Configure properties

You need to configure Ledger and Auditor to make the detection properly work.

For the properties of Ledger, you need to configure the following entries:


You first need to set scalar.dl.ledger.auditor.enabled to true to let Ledger know if the ScalarDL system uses Auditor. Note that you also need to enable scalar.dl.ledger.proof.enabled and set a proper private key to scalar.dl.ledger.proof.private_key_path since Auditor uses AssetProof to work. If they are not properly and consistently configured, Ledger will throw an exception.

Also, Ledger manages an Auditor's certificate (i.e., Auditor needs to register its certificate to Ledger) and uses the certificate to validate a request signed by Auditor's private key to identify the request origin; thus, the certificate holder ID (scalar.dl.ledger.auditor.cert_holder_id) and version (scalar.dl.ledger.auditor.cert_version) are required to be set as well. By default, Ledger assumes Auditor registers its certificate with a name auditor and version 1.

For the properties of Auditor, you need to configure the following entries:


Auditor manages a key pair to sign a request before sending the request to Ledger and validate a request given from Ledger, so you need to set scalar.dl.auditor.cert_path and scalar.dl.auditor.private_key_path properly.

As similarly to Ledger, Auditor manages a Ledger's certificate (i.e., Ledger registers its certificate to Auditor) and uses the certificate to validate a request signed by Ledger's private key; thus, the certificate holder ID (scalar.dl.auditor.ledger.cert_holder_id=ledger) and version (scalar.dl.auditor.ledger.cert_version) are required. By default, Auditor assumes Ledger registers its certificate with a name ledger and version 1.

Other values are optional here but they need to be updated depending on an environment. For example, if you place Ledger and Auditor in different hosts, you need to update for Auditor to be able to access Ledger. Please check the configuration file for more detail.

Start Ledger and Auditor

Please start Ledger and Auditor in your own way. For example, if you use the built-in command line tools, do as follows:


bin/scalar-ledger --properties


bin/scalar-auditor --properties

You can also use the containers that are available in the GitHub Container Registry. See scalardl-samples repo for more details about how to use the containers.

Register each certificate of Ledger and Auditor

As we explained, Ledger needs to register its certificate to Auditor, and Auditor needs to register its certificate to Ledger. This can be done by registering it as a client as follows:

Ledger registers its certificate to Auditor

client/bin/scalardl register-cert --properties

Auditor registers its certificate to Ledger

client/bin/scalardl register-cert --properties

Please configure and properly. (This document assumes you know how to configure properly.) Note that scalar.dl.client.cert_holder_id has to be properly set to match with the one configured in Ledger and Auditor respectively.

Register your certificate

You also need to update the properties file of a client before interacting with ScalarDL with Auditor. Please update the following entries:


Then, you can register your certificate just like you have been doing usually (without Auditor).

client/bin/scalardl register-cert --properties

Note that this registers the certificate to both Ledger and Auditor.

Register your contracts

For registering contracts, you can also do as usual.

client/bin/scalardl register-contract --properties --contract-id StateUpdater --contract-binary-name com.org1.contract.StateUpdater --contract-class-file build/classes/java/main/com/org1/contract/StateUpdater.class

Note that this registers the contract to both Ledger and Auditor.

Execute the contract

Now you are ready to execute the contract with the following command as usual.

client/bin/scalardl execute-contract --properties --contract-id StateUpdater --contract-argument '{"asset_id":"some_asset", "state":3}'

Note that this triggers a little complex protocol between Ledger and Auditor to make them go to the same states without trusting each other. During the execution, it may detect inconsistencies between them if there is tampering in one of the components.

Validate the states of Ledger and Auditor

You can also always validate the states of Ledger and Auditor to see if they are consistent. However, validating the states in the Auditor mode uses contract execution; thus, you first need to register ValidateLedger contract as follows. Note that validate-ledger is the default contract ID that the client specifies when doing validation.

client/bin/scalardl register-contract --properties --contract-id validate-ledger --contract-binary-name com.scalar.dl.client.contract.ValidateLedger --contract-class-file /path/to/ValdateLedger.class

Then, you can issue the validate-ledger command just like as usually you do.

client/bin/scalardl validate-ledger --properties --asset-id="some_asset"

If you want to change the contract ID of ValidateLedger, you need to change the following configuration to let the client know about it.