Key Management Backed by Azure Key Vault

Creation of Kaleido CloudHSM service in Kaleido is a two step process. First, you specify the type and access details to Azure Key Vault as a configuration under the environment. This can be referenced by one or more CloudHSM service instances created in the same membership. Next you create the CloudHSM service using the configuration created belo.

Create CloudHSM configuration for Azure Key Vault

The configuration for Azure Key Vault has the following mandatory parameters:

The following is a sample POST request to create an Azure key vault cloudhsm configuration:

Create Cloud HSM service

Using the configuration created above, cloud HSM service can be created using the request fields:

FieldUsagenameUser-defined name for the servicemembership_idID of membership under which this service is availableserviceType of service. Must be cloudhsmdetails-- cloudhsm_idID of the configuration created in the previous step

The following is a sample POST request to create a Cloud HSM service that uses an Azure Key Vault backend provider:

https://console.kaleido.io/api/v1/consortia/:consortia_id/environments/:environment_id/services

{
 "name": "cloudhsm-azure",
 "membership_id": "",
 "service": "cloudhsm",
 "details": {
   "cloudhsm_id": ""
 }
}

Transaction Signing with Azure Key Vault

Transactions can be sent to the Kaleido CloudHSM service by specifying a from address that corresponds to a SECP256K1 type key that is present in the Azure Key Vault. Any of RPC, WSS or the API Gateway interfaces can be used to send transactions. The URLs for the interfaces can be obtained by querying the service's /status route

A sample GET request to obtain the service status is as below:

https://console.kaleido.io/api/v1/consortia/:consortia_id/environments/:environment_id/services/:service_id/status

When a eth_sendTransaction request is received by the Kaleido CloudHSM service, it uses the from address to determine whether the configured backend cloud HSM contains the keys for the address. The Kaleido CloudHSM service sends a /sign request with the KEY ID of the from address and the transaction payload to Azure Key Vault to sign. If the request succeeds, Key Vault returns the signature, from which the Ethereum signature parameters - R, S and V are extracted, as well as making sure the S value is compatible with Ethereum's malleability protection rule, and included in the transaction before sending it to the Ethereum blockchain node in the Kaleido environment that the service is bound to.