# AWS CloudHSM KeyStore Java class for Client SDK 5
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The AWS CloudHSM `KeyStore` class provides a special-purpose PKCS12 key store. This key store can store certificates along with your key data and correlate them to key data stored on AWS CloudHSM. The AWS CloudHSM `KeyStore` class implements the `KeyStore` Service Provider Interface (SPI) of the Java Cryptography Extension (JCE). For more information about using `KeyStore`, see [Class KeyStore](https://devdocs.io/openjdk~8/java/security/keystore).

**Note**  
Because certificates are public information, and to maximize storage capacity for cryptographic keys, AWS CloudHSM does not support storing certificates on HSMs.

## Choose the appropriate key store for AWS CloudHSM Client SDK 5
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The AWS CloudHSM Java Cryptographic Extension (JCE) provider offers a special-purpose AWS CloudHSM KeyStore. The AWS CloudHSM `KeyStore` class supports offloading key operations to the HSM, local storage of certificates and certificate-based operations.

Load the special-purpose CloudHSM KeyStore as follows:

```
KeyStore ks = KeyStore.getInstance("CloudHSM")
```

## Initialize the AWS CloudHSM KeyStore Client SDK 5
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Log into the AWS CloudHSM KeyStore the same way that you log into the JCE provider. You can use either environment variables or the system property file, and you should log in before you start using the CloudHSM KeyStore. For an example of logging into an HSM using the JCE provider, see [Login to an HSM](https://github.com/aws-samples/aws-cloudhsm-jce-examples/blob/sdk5/src/main/java/com/amazonaws/cloudhsm/examples/LoginRunner.java).

If desired, you can specify a password to encrypt the local PKCS12 file which holds key store data. When you create the AWS CloudHSM Keystore, you set the password and provide it when using the load, set and get methods.

Instantiate a new CloudHSM KeyStore object as follows:

```
ks.load(null, null);
```

Write keystore data to a file using the `store` method. From that point on, you can load the existing keystore using the `load` method with the source file and password as follows: 

```
ks.load(inputStream, password);
```

## Use AWS CloudHSM KeyStore or AWS CloudHSM Client SDK 5
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AWS CloudHSM KeyStore complies with the JCE [Class KeyStore](https://devdocs.io/openjdk~8/java/security/keystore) specification and provides the following functions.
+ `load`

  Loads the key store from the given input stream. If a password was set when saving the key store, this same password must be provided for the load to succeed. Set both parameters to null to initialize an new empty key store.

  ```
  KeyStore ks = KeyStore.getInstance("CloudHSM");
  ks.load(inputStream, password);
  ```
+ `aliases`

  Returns an enumeration of the alias names of all entries in the given key store instance. Results include objects stored locally in the PKCS12 file and objects resident on the HSM. 

  **Sample code:**

  ```
  KeyStore ks = KeyStore.getInstance("CloudHSM");
  for(Enumeration<String> entry = ks.aliases(); entry.hasMoreElements();) {    
      String label = entry.nextElement();    
      System.out.println(label);
  }
  ```
+ `containsalias`

  Returns true if the key store has access to at least one object with the specified alias. The key store checks objects stored locally in the PKCS12 file and objects resident on the HSM.
+ `deleteEntry`

  Deletes a certificate entry from the local PKCS12 file. Deleting key data stored in an HSM is not supported using the AWS CloudHSM KeyStore. You can delete keys using the `destroy` method of the [Destroyable](https://devdocs.io/openjdk~8/javax/security/auth/destroyable#destroy--) interface.

  ```
  ((Destroyable) key).destroy();
  ```
+ `getCertificate`

  Returns the certificate associated with an alias if available. If the alias does not exist or references an object which is not a certificate, the function returns NULL. 

  ```
  KeyStore ks = KeyStore.getInstance("CloudHSM");
  Certificate cert = ks.getCertificate(alias);
  ```
+ `getCertificateAlias`

  Returns the name (alias) of the first key store entry whose data matches the given certificate. 

  ```
  KeyStore ks = KeyStore.getInstance("CloudHSM");
  String alias = ks.getCertificateAlias(cert);
  ```
+ `getCertificateChain`

  Returns the certificate chain associated with the given alias. If the alias does not exist or references an object which is not a certificate, the function returns NULL. 
+ `getCreationDate`

  Returns the creation date of the entry identified by the given alias. If a creation date is not available, the function returns the date on which the certificate became valid.
+ `getKey`

  GetKey is passed to the HSM and returns a key object corresponding to the given label. As `getKey` directly queries the HSM, it can be used for any key on the HSM regardless of whether it was generated by the KeyStore. 

  ```
  Key key = ks.getKey(keyLabel, null);
  ```
+ `isCertificateEntry`

  Checks if the entry with the given alias represents a certificate entry. 
+ `isKeyEntry`

  Checks if the entry with the given alias represents a key entry. The action searches both the PKCS12 file and the HSM for the alias. 
+ `setCertificateEntry`

  Assigns the given certificate to the given alias. If the given alias is already being used to identify a key or certificate, a `KeyStoreException` is thrown. You can use JCE code to get the key object and then use the KeyStore `SetKeyEntry` method to associate the certificate to the key.
+ `setKeyEntry` with `byte[]` key

  **This API is currently unsupported with Client SDK 5.**
+ `setKeyEntry` with `Key` object

  Assigns the given key to the given alias and stores it inside the HSM. If the key does not already exist inside the HSM, it will be imported into the HSM as an extractable session key.

  If the `Key` object is of type `PrivateKey`, it must be accompanied by a corresponding certificate chain. 

  If the alias already exists, the `SetKeyEntry` call throws a `KeyStoreException` and prevents the key from being overwritten. If the key must be overwritten, use KMU or JCE for that purpose. 
+ `engineSize`

  Returns the number of entries in the keystore.
+ `store`

  Stores the key store to the given output stream as a PKCS12 file and secures it with the given password. In addition, it persists all loaded keys (which are set using `setKey` calls).