# Connect an Amazon CloudHSM key store
New Amazon CloudHSM key stores are not connected. Before you can create and use Amazon KMS keys in your Amazon CloudHSM key store, you need to connect it to its associated Amazon CloudHSM cluster. You can connect and disconnect your Amazon CloudHSM key store at any time, and [view its connection state](view-keystore.md#view-keystore-console).
You are not required to connect your Amazon CloudHSM key store. You can leave an Amazon CloudHSM key store in a disconnected state indefinitely and connect it only when you need to use it. However, you might want to test the connection periodically to verify that the settings are correct and it can be connected.
**Note**
Amazon CloudHSM key stores have a `DISCONNECTED` connection state only when the key store has never been connected or you explicitly disconnect it. If your Amazon CloudHSM key store connection state is `CONNECTED` but you are having trouble using it, make sure that its associated Amazon CloudHSM cluster is active and contains at least one active HSMs. For help with connection failures, see [Troubleshooting a custom key store](fix-keystore.md).
When you connect an Amazon CloudHSM key store, Amazon KMS finds the associated Amazon CloudHSM cluster, connects to it, logs into the Amazon CloudHSM client as the [`kmsuser` crypto user](keystore-cloudhsm.md#concept-kmsuser) (CU), and then rotates the `kmsuser` password. Amazon KMS remains logged into the Amazon CloudHSM client as long as the Amazon CloudHSM key store is connected.
To establish the connection, Amazon KMS creates a [security group](https://docs.amazonaws.cn/vpc/latest/userguide/VPC_SecurityGroups.html) named `kms-` in the virtual private cloud (VPC) of the cluster. The security group has a single rule that allows inbound traffic from the cluster security group. Amazon KMS also creates an [elastic network interface](https://docs.amazonaws.cn/vpc/latest/userguide/VPC_ElasticNetworkInterfaces.html) (ENI) in each Availability Zone of the private subnet for the cluster. Amazon KMS adds the ENIs to the `kms-` security group and the security group for the cluster. The description of each ENI is `KMS managed ENI for cluster `.
The connection process can take an extended amount of time to complete; up to 20 minutes.
Before you connect the Amazon CloudHSM key store, verify that it meets the requirements.
+ Its associated Amazon CloudHSM cluster must contain at least one active HSM. To find the number of HSMs in the cluster, view the cluster in the Amazon CloudHSM console or use the [DescribeClusters](https://docs.amazonaws.cn/cloudhsm/latest/APIReference/API_DescribeClusters.html) operation. If necessary, you can [add an HSM](https://docs.amazonaws.cn/cloudhsm/latest/userguide/add-remove-hsm.html).
+ The cluster must have a [`kmsuser` crypto user](create-keystore.md#kmsuser-concept) (CU) account, but that CU cannot be logged into the cluster when you connect the Amazon CloudHSM key store. For help with logging out, see [How to log out and reconnect](fix-keystore.md#login-kmsuser-2).
+ The connection state of the Amazon CloudHSM key store cannot be `DISCONNECTING` or `FAILED`. To view the connection state, use the Amazon KMS console or the [DescribeCustomKeyStores](https://docs.amazonaws.cn/kms/latest/APIReference/API_DescribeCustomKeyStores.html) response. If the connection state is `FAILED`, disconnect the custom key store, fix the problem, and then connect it.
For help with connection failures, see [How to fix a connection failure](fix-keystore.md#fix-keystore-failed).
When your Amazon CloudHSM key store is connected, you can [create KMS keys in it](create-cmk-keystore.md) and use existing KMS keys in [cryptographic operations](manage-cmk-keystore.md#use-cmk-keystore).
## Connect and reconnect to your Amazon CloudHSM key store
You can connect, or reconnect, your Amazon CloudHSM key store in the Amazon KMS console or by using the [ConnectCustomKeyStore](https://docs.amazonaws.cn/kms/latest/APIReference/API_ConnectCustomKeyStore.html) operation.
### Using the Amazon KMS console
To connect an Amazon CloudHSM key store in the Amazon Web Services Management Console, begin by selecting the Amazon CloudHSM key store from the **Custom key stores** page. The connection process can take up to 20 minutes to complete.
1. Sign in to the Amazon Web Services Management Console and open the Amazon Key Management Service (Amazon KMS) console at [https://console.amazonaws.cn/kms](https://console.amazonaws.cn/kms).
1. To change the Amazon Web Services Region, use the Region selector in the upper-right corner of the page.
1. In the navigation pane, choose **Custom key stores**, **Amazon CloudHSM key stores**.
1. Choose the row of the Amazon CloudHSM key store you want to connect.
If the connection state of the Amazon CloudHSM key store is **Failed**, you must [disconnect the custom key store](disconnect-keystore.md#disconnect-keystore-console) before you connect it.
1. From the **Key store actions** menu, choose **Connect**.
Amazon KMS begins the process of connecting your custom key store. It finds the associated Amazon CloudHSM cluster, builds the required network infrastructure, connects to it, logs into the Amazon CloudHSM cluster as the `kmsuser` CU, and rotates the `kmsuser` password. When the operation completes, the connection state changes to **Connected**.
If the operation fails, an error message appears that describes the reason for the failure. Before you try to connect again, [view the connection state](view-keystore.md) of your Amazon CloudHSM key store. If it is **Failed**, you must [disconnect the custom key store](disconnect-keystore.md#disconnect-keystore-console) before you connect it again. If you need help, see [Troubleshooting a custom key store](fix-keystore.md).
**Next:** [Create a KMS key in an Amazon CloudHSM key store](create-cmk-keystore.md).
### Using the Amazon KMS API
To connect a disconnected Amazon CloudHSM key store, use the [ConnectCustomKeyStore](https://docs.amazonaws.cn/kms/latest/APIReference/API_ConnectCustomKeyStore.html) operation. The associated Amazon CloudHSM cluster must contain at least one active HSM and the connection state cannot be `FAILED`.
The connection process takes an extended amount of time to complete; up to 20 minutes. Unless it fails quickly, the operation returns an HTTP 200 response and a JSON object with no properties. However, this initial response does not indicate that the connection was successful. To determine the connection state of the custom key store, see the [DescribeCustomKeyStores](https://docs.amazonaws.cn/kms/latest/APIReference/API_DescribeCustomKeyStores.html) response.
The examples in this section use the [Amazon Command Line Interface (Amazon CLI)](http://www.amazonaws.cn/cli/), but you can use any supported programming language.
To identify the Amazon CloudHSM key store, use its custom key store ID. You can find the ID on the **Custom key stores** page in the console or by using the [DescribeCustomKeyStores](https://docs.amazonaws.cn/kms/latest/APIReference/API_DescribeCustomKeyStores.html) operation with no parameters. Before running this example, replace the example ID with a valid one.
```
$ aws kms connect-custom-key-store --custom-key-store-id cks-1234567890abcdef0
```
To verify that the Amazon CloudHSM key store is connected, use the [DescribeCustomKeyStores](https://docs.amazonaws.cn/kms/latest/APIReference/API_DescribeCustomKeyStores.html) operation. By default, this operation returns all custom keys stores in your account and Region. But you can use either the `CustomKeyStoreId` or `CustomKeyStoreName` parameter (but not both) to limit the response to particular custom key stores. The `ConnectionState` value of `CONNECTED` indicates that the custom key store is connected to its Amazon CloudHSM cluster.
**Note**
The `CustomKeyStoreType` field was added to the `DescribeCustomKeyStores` response to distinguish Amazon CloudHSM key stores from external key stores.
```
$ aws kms describe-custom-key-stores --custom-key-store-id cks-1234567890abcdef0
{
"CustomKeyStores": [
"CustomKeyStoreId": "cks-1234567890abcdef0",
"CustomKeyStoreName": "ExampleCloudHSMKeyStore",
"CloudHsmClusterId": "cluster-1a23b4cdefg",
"CustomKeyStoreType": "AWS_CLOUDHSM",
"TrustAnchorCertificate": "",
"CreationDate": "1.499288695918E9",
"ConnectionState": "CONNECTED"
],
}
```
If the `ConnectionState` value is failed, the `ConnectionErrorCode` element indicates the reason for the failure. In this case, Amazon KMS could not find an Amazon CloudHSM cluster in your account with the cluster ID `cluster-1a23b4cdefg`. If you deleted the cluster, you can [restore it from a backup](https://docs.amazonaws.cn/cloudhsm/latest/userguide/create-cluster-from-backup.html) of the original cluster and then [edit the cluster ID](update-keystore.md) for the custom key store. For help responding to a connection error code, see [How to fix a connection failure](fix-keystore.md#fix-keystore-failed).
```
$ aws kms describe-custom-key-stores --custom-key-store-id cks-1234567890abcdef0
{
"CustomKeyStores": [
"CustomKeyStoreId": "cks-1234567890abcdef0",
"CustomKeyStoreName": "ExampleKeyStore",
"CloudHsmClusterId": "cluster-1a23b4cdefg",
"CustomKeyStoreType": "AWS_CLOUDHSM",
"TrustAnchorCertificate": "",
"CreationDate": "1.499288695918E9",
"ConnectionState": "FAILED"
"ConnectionErrorCode": "CLUSTER_NOT_FOUND"
],
}
```