Confidential Space Enclave Signer

Confidential Space backend is used in conjunction with signatory-io/tee-signer, its counterpart running inside Google Cloud Confidential Space, a secure execution environment that provides hardware-based memory encryption and integrity verification.

All keys imported into tee-signer or generated by it never leave the enclave in a plain text form. As the enclave has no persistent storage, all sensitive data is stored by the parent instance in encrypted form. The keystone of this model is a carefully chosen Google Cloud KMS policy which permits the decryption of such data only by an actor possessing proper authentication credentials and running inside the Confidential Space environment.

Prerequisites

For detailed setup instructions, see GCP Confidential Space Setup Guide.

You will need:

• A Workload Identity Pool (WIP) Provider path for authentication
• A KMS encryption key path for encrypting/decrypting private keys
• Network access to the Confidential Space enclave running tee-signer

Configuration

Field	Environment variable	Type	Default	Required	Description
host	CONFIDENTIAL_SPACE_HOST	string		✅	Host address of the Confidential Space enclave running tee-signer
port	CONFIDENTIAL_SPACE_PORT	string	2000		TCP port of tee-signer service
wip_provider_path	GCP_WIP_PROVIDER_PATH	string		✅	Workload Identity Pool Provider path for authentication
encryption_key_path	GCP_KMS_ENCRYPTION_KEY_PATH	string		✅	KMS key path used by enclave to encrypt/decrypt private keys
storage		StorageConfig			Key storage configuration

StorageConfig

Encrypted keys can be stored in different backends. The storage configuration is optional - if omitted, local file storage will be used by default.

Field	Type	Description
driver	string	Storage driver: "file", "gcp", or "firestore"
config	yaml.Node	Storage-specific configuration

Local File Storage

For local file storage, the config field is expected to be a single string containing a full file path. Environment variables are allowed and will be expanded.

If local storage is specified without a config, the default file ${BASE_DIR}/confidential_space_keys.json will be used.

Google Cloud Firestore Storage

For Google Cloud Firestore storage, the config field should contain:

Field	Type	Required	Description
application_credentials	string	OPTIONAL	Path to the GCP application token JSON file (overrides GOOGLE_APPLICATION_CREDENTIALS environment variable)
application_credentials_data	string	OPTIONAL	GCP application token JSON data (overrides application_credentials)
project	string	✅	GCP project ID
database	string	✅	Firestore database name
table	string		Collection name (default: "encrypted_keys")

The Firestore storage driver supports both gcp and firestore as driver names for compatibility.

Example

For complete setup instructions, see GCP Confidential Space Setup Guide.

base_dir: ${HOME}/.signatory
server:
  # Address for the main HTTP server to listen on
  address: :6732
  # Address for the utility HTTP server to listen on
  utility_address: :9583

vaults:
  confidentialspace:
    driver: confidentialspace
    config:
      host: 10.0.0.100
      port: 2000
      wip_provider_path: projects/123456789/locations/global/workloadIdentityPools/my-pool/providers/my-provider
      encryption_key_path: projects/my-project/locations/global/keyRings/my-keyring/cryptoKeys/my-key

Importing

Confidential Space backend supports importing of pre-existing plain text keys in either PEM, DER or Base58 format using signatory-cli import command. The key will be passed to the enclave in open form and the latter will return its encrypted version.

Key Generation

More secure way of getting keys into the enclave is to generate them on the enclave side using signatory-cli generate command:

Usage:
  signatory-cli generate [flags]

Flags:
  -h, --help           help for generate
  -n, --num int        Number of keys to generate (default 1)
  -t, --type string    Key algorithm: [tz1, tz2, tz3, tz4, ed25519, secp256k1, p256, bls] (default "ed25519")
  -v, --vault string   Vault name for importing

Global Flags:
      --base-dir string   Base directory. Takes priority over one specified in config
  -c, --config string     Config file path (default "/etc/signatory.yaml")
      --json-log          Use JSON structured logs
      --log string        Log level: [error, warn, info, debug, trace] (default "info")

Example:

signatory-cli generate -v confidentialspace -t bls

Network Communication

The Confidential Space backend communicates with the enclave over TCP. The enclave must be accessible from the network where Signatory is running. The communication protocol is based on CBOR-encoded RPC messages for efficiency and security.

Key Storage

Local File Storage

Encrypted keys are stored in a JSON file with the following structure:

[
  {
    "public_key_hash": "tz4...",
    "encrypted_private_key": "..."
  }
]

The public_key_hash field contains the Tezos address (Base58 encoded), and the encrypted_private_key field contains the KMS-encrypted private key data.

Firestore Storage

When using Firestore storage, encrypted keys are stored as documents in a Firestore collection with the following structure:

{
  "pkh": "tz4...",
  "value": "..."
}

Where pkh contains the Tezos address (Base58 encoded) and value contains the KMS-encrypted private key data.