encryption-at-rest: Update

encryption-at-rest.md

@@ -10,6 +10,8 @@ Encryption at rest means that data is encrypted when it is stored. For databases
 
 TiKV supports encryption at rest starting from v4.0.0. The feature allows TiKV to transparently encrypt data files using [AES](https://en.wikipedia.org/wiki/Advanced_Encryption_Standard) in [CTR](https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation)  mode. To enable encryption at rest, an encryption key must be provided by user and this key is called master key. The master key can be provided via AWS KMS (recommended), or specifying a key stored as plaintext in a file. TiKV automatically rotates data keys that it used to encrypt actual data files. Manually rotating the master key can be done occasionally. Note that encryption at rest only encrypts data at rest (namely, on disk) and not while data is transferred over network. It is advised to use TLS together with encryption at rest.
 
+Using AWS KMS is also possible for on-premise deployments.
+
 Also from v4.0.0, BR supports S3 server-side encryption (SSE) when backing up to S3. A customer owned AWS KMS key can also be used together with S3 server-side encryption.
 
 ## Warnings
@@ -39,14 +41,27 @@ Data keys are generated by TiKV and passed to the underlying storage engine (nam
 
 Regardless of data encryption method, data keys are encrypted using AES256 in GCM mode for additional authentication. This required the master key to be 256 bits (32 bytes), when passing from file instead of KMS.
 
+### Key creation
+
+Go to the [AWS KMS](https://console.aws.amazon.com/kms) on the AWS console. Make sure the correct region is selected on the top right corner of your console. Make  and click "Create a key". Select "Symmetric" as Key type. After this you can set an alias an description and set tags.
+
+It is also possible to do this with the AWS Cli:
+
+```
+aws --region us-west-2 kms create-key
+aws --region us-west-2 kms create-alias --alias-name "alias/tidb-tde" --target-key-id 0987dcba-09fe-87dc-65ba-ab0987654321
+```
+
+The `key-id` for the second step is giving in the output of the first command.
+
 ### Configure encryption
 
 To enable encryption, you can add the encryption section in TiKV's configuration file:
 
 ```
 [security.encryption]
-data-encryption-method = aes128-ctr
-data-key-rotation-period = 7d
+data-encryption-method = "aes128-ctr"
+data-key-rotation-period = "7d"
 ```
 
 Possible values for `data-encryption-method` are "aes128-ctr", "aes192-ctr", "aes256-ctr" and "plaintext". The default value is "plaintext", which means encryption is not turned on. `data-key-rotation-period` defines how often TiKV rotates the data key. Encryption can be turned on for a fresh TiKV cluster, or an existing TiKV cluster, though only data written after encryption is enabled is guaranteed to be encrypted. To disable encryption, remove `data-encryption-method` in the configuration file, or reset it to "plaintext", and restart TiKV. To change encryption method, update `data-encryption-method` in the configuration file and restart TiKV.
@@ -61,7 +76,9 @@ region = "us-west-2"
 endpoint = "https://kms.us-west-2.amazonaws.com"
 ```
 
-The `key-id` specifies the key id for the KMS CMK. The `region` is the AWS region name for the KMS CMK. The `endpoint` is optional and doesn't need to be specified normally, unless you are using a AWS KMS compatible service from a non-AWS vendor.
+The `key-id` specifies the key id for the KMS CMK. The `region` is the AWS region name for the KMS CMK. The `endpoint` is optional and doesn't need to be specified normally, unless you are using a AWS KMS compatible service from a non-AWS vendor or need to use a [VPC endpoint for KMS](https://docs.aws.amazon.com/kms/latest/developerguide/kms-vpc-endpoint.html).
+
+It is possible to use [multi-Region keys](https://docs.aws.amazon.com/kms/latest/developerguide/multi-region-keys-overview.html). For this you need to setup a primary key in a specific region and add replica keys in the regions you require.
 
 To specify a master key that's stored in a file, the master key configuration would look like the following: