The configuration is handled via the config file: walt.yaml, which overwrites the default config that is packaged within the jar file: src/main/resources/walt-default.yaml
privateKey:it will be used to sign the transactions. By default, transactions are signed by that private key.The keys are in the format that is exported from MetaMask. e.g.: 51ada6337f405cd61f27aa0f604e0ea97c8bdecfd156a646b4cc20554cfb662f
keys:a mapping of address and their private keys that are exported from MetaMask. In some use cases, you can choose which private key is used to sign the transaction.