Configure Google Cloud KMS for CMEK

Skip this step if you already have a key ring to reuse. Key rings are regional. Choose a single-region US location such as us-east5 that matches the Anthropic geography you are configuring. Multi-region locations like us and global are not supported.

gcloud kms keyrings create <your-keyring-name> \
  --project=<your-project-id> \
  --location=<region>

Create a symmetric key with the ENCRYPT_DECRYPT purpose. HSM protection is strongly recommended: Cloud KMS HSM keys are FIPS 140-2 Level 3 validated, and the cost delta over software keys is small.

gcloud kms keys create <your-key-name> \
  --project=<your-project-id> \
  --location=<region> \
  --keyring=<your-keyring-name> \
  --purpose=encryption \
  --protection-level=hsm

For software protection instead, omit --protection-level=hsm. Nothing else in this guide changes.

You can also create the key from the Google Cloud Console. Open the key ring, click Create key, select Generated key, set the purpose and algorithm to symmetric encrypt and decrypt, and choose HSM under protection level.

Two key-level IAM bindings are required. Both are scoped to the single crypto key, not project-wide or keyring-wide.

Encrypt and decrypt, which Anthropic uses to encrypt and decrypt the data keys that protect your workspace data (envelope encryption):

gcloud kms keys add-iam-policy-binding <your-key-name> \
  --project=<your-project-id> \
  --location=<region> \
  --keyring=<your-keyring-name> \
  --member="serviceAccount:anthropic-cmek-client-us@gcp-anthropic-cmek-clients.iam.gserviceaccount.com" \
  --role=roles/cloudkms.cryptoKeyEncrypterDecrypter

Viewer, for the metadata read (cryptoKeys.get) Anthropic performs at startup to validate the key's purpose and algorithm:

gcloud kms keys add-iam-policy-binding <your-key-name> \
  --project=<your-project-id> \
  --location=<region> \
  --keyring=<your-keyring-name> \
  --member="serviceAccount:anthropic-cmek-client-us@gcp-anthropic-cmek-clients.iam.gserviceaccount.com" \
  --role=roles/cloudkms.viewer

From the Console, select the key, open the Permissions panel, click Grant access, and add the service account with both the Cloud KMS CryptoKey Encrypter/Decrypter and Cloud KMS Viewer roles. Make sure you are on the key's permissions page, not the key ring or project, so the grant is scoped to this key only.

You pass this to Anthropic when you register the key. The format is:

projects/<your-project-id>/locations/<region>/keyRings/<your-keyring-name>/cryptoKeys/<your-key-name>

Retrieve it with:

gcloud kms keys describe <your-key-name> \
  --project=<your-project-id> \
  --location=<region> \
  --keyring=<your-keyring-name> \
  --format="value(name)"

From the Console, open the key's details page and click Copy resource name.

Create an external key configuration through the Admin API, using the resource name from the previous step.

curl -sS https://api.anthropic.com/v1/organizations/external_keys \
  -H "x-api-key: <anthropic-admin-api-key>" \
  -H "anthropic-version: 2023-06-01" \
  -H "content-type: application/json" \
  -d '{
    "display_name": "<friendly-name>",
    "geo": "us",
    "provider_config": {
      "type": "gcp",
      "key_name": "projects/<your-project-id>/locations/<region>/keyRings/<your-keyring-name>/cryptoKeys/<your-key-name>"
    }
  }'

The response contains the external key ID:

{
  "type": "external_key",
  "id": "ekey_<id>",
  "display_name": "<friendly-name>"
}

Trigger an encrypt and decrypt round-trip against your key.

curl -sS -X POST https://api.anthropic.com/v1/organizations/external_keys/ekey_<id>/validate \
  -H "x-api-key: <anthropic-admin-api-key>" \
  -H "anthropic-version: 2023-06-01" \
  -H "content-type: application/json" -d '{}'

A successful response looks like this:

{ "type": "external_key_validation", "status": "success", "error": null }

If validation fails, common causes are:

• VPC Service Controls: if a service perimeter protects Cloud KMS in your project, add Anthropic to an access level on the perimeter (or exclude the key's project) so Anthropic can reach the key.
• Domain restricted sharing: the constraints/iam.allowedPolicyMemberDomains org policy can strip the Anthropic service account binding (see the note above). Confirm the binding is present with gcloud kms keys get-iam-policy <your-key-name> --project=<your-project-id> --location=<region> --keyring=<your-keyring-name>.
• Disabled or destroyed key version: confirm the key's primary version is enabled, and not disabled, scheduled for destruction, or destroyed.