# Data encryption using Amazon KMS
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Storage Gateway uses SSL/TLS (Secure Socket Layers/Transport Layer Security) to encrypt data that is transferred between your gateway appliance and Amazon storage. By default, Storage Gateway uses Amazon S3-Managed Encryption Keys (SSE-S3) to server-side encrypt all data it stores in Amazon S3. You have an option to use the Storage Gateway API to configure your gateway to encrypt data stored in the cloud using server-side encryption with Amazon Key Management Service (SSE-KMS) keys.

**Important**  
When you use an Amazon KMS key for server-side encryption, you must choose a symmetric key. Storage Gateway does not support asymmetric keys. For more information, see [Using symmetric and asymmetric keys](https://docs.amazonaws.cn/kms/latest/developerguide/symmetric-asymmetric.html) in the *Amazon Key Management Service Developer Guide*.

**Encrypting a file share**  
For a file share, you can configure your gateway to encrypt your objects with Amazon KMS–managed keys by using SSE-KMS. For information on using the Storage Gateway API to encrypt data written to a file share, see [CreateNFSFileShare](https://docs.amazonaws.cn/storagegateway/latest/APIReference/API_CreateNFSFileShare.html) in the *Amazon Storage Gateway API Reference*.

**Encrypting a volume**  
For cached and stored volumes, you can configure your gateway to encrypt volume data stored in the cloud with Amazon KMS–managed keys by using the Storage Gateway API. You can specify one of the managed keys as the KMS key. The key that you use to encrypt your volume can't be changed after the volume is created. For information on using the Storage Gateway API to encrypt data written to a cached or stored volume, see [CreateCachediSCSIVolume](https://docs.amazonaws.cn/storagegateway/latest/APIReference/API_CreateCachediSCSIVolume.html) or [CreateStorediSCSIVolume](https://docs.amazonaws.cn/storagegateway/latest/APIReference/API_CreateStorediSCSIVolume.html) in the *Amazon Storage Gateway API Reference*.

**Encrypting a tape**  
For a virtual tape, you can configure your gateway to encrypt tape data stored in the cloud with Amazon KMS–managed keys by using the Storage Gateway API. You can specify one of the managed keys as the KMS key. The key that you use to encrypt your tape data can't be changed after the tape is created. For information on using the Storage Gateway API to encrypt data written to a virtual tape, see [CreateTapes](https://docs.amazonaws.cn/storagegateway/latest/APIReference/API_CreateTapes.html) in the *Amazon Storage Gateway API Reference*.

When using Amazon KMS to encrypt your data*,* keep the following in mind:
+ Your data is encrypted at rest in the cloud. That is, the data is encrypted in Amazon S3.
+ IAM users must have the required permissions to call the Amazon KMS API operations. For more information, see [Using IAM policies with Amazon KMS](https://docs.amazonaws.cn/kms/latest/developerguide/iam-policies.html) in the *Amazon Key Management Service Developer Guide*.
+ If you delete or deactivate your Amazon Amazon KMS key or revoke the grant token, you can't access the data on the volume or tape. For more information, see [Deleting KMS keys](https://docs.amazonaws.cn/kms/latest/developerguide/deleting-keys.html) in the *Amazon Key Management Service Developer Guide*.
+ If you create a snapshot from a volume that is KMS-encrypted, the snapshot is encrypted. The snapshot inherits the volume's KMS key.
+ If you create a new volume from a snapshot that is KMS-encrypted, the volume is encrypted. You can specify a different KMS key for the new volume.
**Note**  
Storage Gateway doesn't support creating an unencrypted volume from a recovery point of a KMS-encrypted volume or a KMS-encrypted snapshot.

For more information about Amazon KMS, see [What is Amazon Key Management Service?](https://docs.amazonaws.cn/kms/latest/developerguide/overview.html)