Help Center/ Elastic Volume Service/ Service Overview/ EVS Encryption
Updated on 2023-11-03 GMT+08:00
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EVS Encryption

What Is EVS Encryption?

In case your services require encryption for the data stored on EVS disks, EVS provides you with the encryption function. You can encrypt newly created EVS disks.

EVS uses the industry-standard XTS-AES-256 encryption algorithm and keys to encrypt EVS disks. Keys used by encrypted disks are provided by the Key Management Service (KMS) of Data Encryption Workshop (DEW), which is secure and convenient. So you do not need to establish and maintain the key management infrastructure. KMS uses the Hardware Security Module (HSM) that complies with FIPS 140-2 level 3 requirements to protect keys. All user keys are protected by the root key in HSM to prevent key exposure.

The encryption attribute of a disk cannot be changed after the disk is purchased.

For details about how to create an encrypted disk, see Purchase an EVS Disk.

Keys Used for EVS Encryption

Keys provided by KMS include a Default Key and Custom Keys.
  • Default Key: A key that is automatically created by EVS through KMS and named evs/default.

    It cannot be disabled and does not support scheduled deletion.

  • Custom keys: Keys created by users. You can use existing keys or create new ones to encrypt disks. For details, see Key Management Service > Creating a CMK in the Data Encryption Workshop User Guide.

When an encrypted disk is attached, EVS accesses KMS, and KMS sends the data key (DK) to the host memory for use. The disk uses the DK plaintext to encrypt and decrypt disk I/Os. The DK plaintext is only stored in the memory of the host housing the ECS and is not stored persistently on the media. If a custom key is disabled or deleted in KMS, the disk encrypted using this custom key can still use the DK plaintext stored in the host memory. If this disk is later detached, the DK plaintext will be deleted from the memory, and data can be no longer read from or written to the disk. Before you re-attach this encrypted disk, ensure that the custom key is enabled.

If you use a custom key to encrypt disks and this custom key is then disabled or scheduled for deletion, data cannot be read from or written to these disks or may never be restored. See Table 1 for more information.
Table 1 Impact of custom key unavailability

Custom Key Status

Impact

How to Restore

Disabled
  • For an encrypted disk already attached:

    Reads and writes to the disk are normal unless the disk is detached. Once detached, the disk cannot be attached again.

  • For an encrypted disk not attached:

    The disk cannot be attached anymore.

Enable the custom key. For details, see Enabling One or More Custom Keys.

Scheduled deletion

Cancel the scheduled deletion for the custom key. For details, see Canceling the Scheduled Deletion of One or More Custom Keys.

Deleted

Data on the disks can never be restored.

Encryption Scenarios

  • System disk encryption

    System disks are purchased along with servers and cannot be purchased separately. So whether a system disk is encrypted or not depends on the image selected during the server creation. See the following table for details.

    Table 2 Encryption relationship between images and system disks

    Creating Server Using Encrypted Image

    Whether System Disk Will Be Encrypted

    Description

    Yes

    Yes

    For details, see Managing Private Images > Encrypting Images in the Image Management Service User Guide.

    No

    No

    -
  • Data disk encryption

    Data disks can be purchased along with servers or separately. Whether data disks are encrypted depends on their data sources. See the following table for details.

    Table 3 Encryption relationship between backups, snapshots, images, and data disks

    Purchased On

    Method of Purchase

    Whether Data Disk Will Be Encrypted

    Description

    The ECS console

    Purchased together with the server

    Yes/No

    When a data disk is purchased together with a server, you can choose to encrypt the disk or not. For details, see Getting Started > Creating an ECS > Step 1: Configure Basic Settings in the Elastic Cloud Server User Guide.

    The EVS console

    No data source selected

    Yes/No

    When an empty disk is created, you can choose whether to encrypt the disk or not. The encryption attribute of the disk cannot be changed after the disk has been created.

    Creating from a backup

    Yes/No
    • When a disk is created from a backup, you can choose whether to encrypt the disk or not. The encryption attributes of the disk and backup do not need to be the same.
    • When you create a backup for a system or data disk, the encryption attribute of the backup will be the same as that of the disk.

    Creating from a snapshot

    (The snapshot's source disk is encrypted.)

    Yes

    A snapshot created from an encrypted disk is also encrypted.

    Creating from a snapshot

    (The snapshot's source disk is not encrypted.)

    No

    A snapshot created from a non-encrypted disk is not encrypted.

    Creating from an image

    (The image's source disk is encrypted.)

    Yes

    -

    Creating from an image

    (The image's source disk is not encrypted.)

    No

    -

Who Can Use the Encryption Function?

When a user uses the encryption function, the condition varies depending on whether the user is the first one ever in the current region or project to use this function.

  • If the user is the first user, the user needs to follow the prompt to create an agency, which grants KMS Administrator permissions to EVS. Then the user can create and obtain keys to encrypt and decrypt disks.

    The first user must have the KMS Administrator permissions to create the agency. If the user does not have the KMS Administrator permissions, contact the account administrator to grant the permissions first.

  • If the user is not the first user, the user can use encryption directly.