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Updated on 2024-10-24 GMT+08:00

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Server-Side Encryption

You can use server-side encryption to encrypt data uploaded to OBS to improve storage security and compliance. With server-side encryption, the OBS server encrypts the objects uploaded from the client before storing them. When the objects are accessed, the OBS server decrypts the objects and then returns them to the client.

OBS supports three encryption methods: server-side encryption with KMS-managed keys (SSE-KMS), server-side encryption with OBS-managed keys (SSE-OBS), and server-side encryption with customer-provided keys (SSE-C).

**Table 1** Three server-side encryption methods
Comparison Dimension	SSE-KMS	SSE-OBS	SSE-C
Scenarios	Scenarios that require high compliance and security. Keys are generated by third-party validated HSMs. Access to keys is controlled and all operations involving keys are traceable by logs.	Scenarios that require basic encryption and batch processing. OBS does not need to interact with KMS. SSE-OBS features lower access latency and better performance than SSE-KMS	Scenarios that users need to store and manage keys by themself
Key management	KMS generates and keeps keys, and OBS uses the keys to encrypt objects.	OBS generates and keeps keys, and uses the keys to encrypt objects.	A user generates and keeps keys, and OBS uses the keys to encrypt objects.
Encryption algorithm	AES-256 and SM4	AES-256	AES-256
Encryption scope	Bucket level and object level	Bucket level and object level	Object level
Details	SSE-KMS	SSE-OBS	SSE-C

You can refer to the regions that support SSE-KMS on the console If you want to use the SM4 encryption algorithm when enabling SSE-KMS, choose the CN North-Ulanqab1 region.
SSE-OBS is available on the entire Huawei Cloud Chinese Mainland website.
SSE-C is available in the regions where the SSE-C API is supported.

Bucket-level and Object-level Server-Side Encryption

The following table compares bucket-level and object-level server-side encryption.

**Table 2** Comparison between bucket-level and object-level server-side encryption
Item	Bucket-level Encryption	Object-level Encryption
Scenarios	You need to encrypt all objects when they are uploaded to a bucket.	You need to encrypt only some objects or select an encryption method and key each time you upload an object.
Encryption methods	SSE-KMS and SSE-OBS	SSE-KMS, SSE-OBS, and SSE-C
Configuration	You can change your encryption configuration at any time.	You can configure encryption during object upload and the configuration cannot be changed after the upload.
Impacts	If encryption is not enabled for a bucket, you can separately configure encryption when uploading objects to the bucket. If encryption is enabled for a bucket, OBS only encrypts the objects uploaded after encryption is enabled, and does not encrypt those uploaded before. When you upload objects to this bucket, they will inherit the bucket's encryption by default, but you can change the configuration if needed. If you change the encryption configuration for a bucket, only the objects uploaded after the change will inherit the new configuration. Objects uploaded before the change will retain the original configuration. Disabling encryption for a bucket does not change the encryption status of existing objects in the bucket. However, objects uploaded later will not be forcibly encrypted. If necessary, you can manually encrypt subsequent objects when you upload them to the bucket.

Constraints

Only one encryption method can be used each time an object is uploaded. The encryption configuration of an uploaded object cannot be changed.
To use SSE-KMS to encrypt a bucket or the objects in it, you must have kms:cmk:get, kms:cmk:list, kms:cmk:create, kms:dek:create, and kms:dek:crypto permissions granted by using IAM, so that you can upload objects to or download objects from this bucket.
If server-side encryption is disabled for a bucket, the encrypted objects can only be accessed over HTTPS.
A key in use cannot be deleted, or the object encrypted with this key cannot be downloaded.

SSE-KMS

Figure 1 SSE-KMS encryption process

During the encryption in Figure 1, SSE-KMS supports envelope encryption. Customer master keys hosted by KMS are not directly used to encrypt data. Instead, data keys derived from them are used to encrypt data in OBS. OBS stores the encrypted objects and data keys.

Figure 2 SSE-KMS decryption process

During the decryption in Figure 2, KMS decrypts the data keys, uses them to decrypt the objects, and returns the objects to users.

KMS uses Hardware Secure Modules (HSMs) to ensure key security, enabling users to easily create and manage encryption keys. Keys are not displayed in plaintext outside HSMs, which prevents key disclosure. All operations performed on keys are controlled and logged, and usage of all keys is recorded, meeting regulatory compliance requirements.

**Table 3** APIs that support SSE-KMS encryption
Resource	API	Header
Bucket	Creating a Bucket	x-obs-server-side-encryption: Encryption method of a bucket x-obs-server-side-data-encryption: Encryption algorithm for server-side encryption x-obs-server-side-encryption-kms-key-id: KMS master key. If this header is not provided, the default master key will be used. x-obs-sse-kms-key-project-id: ID of the project that the KMS master key belongs to
Bucket	Configuring Bucket Encryption	The encryption configuration is in the body. For details, see Configuring Bucket Encryption.
Object	Uploading Objects - PUT	x-obs-server-side-data-encryption: Encryption algorithm for server-side encryption x-obs-server-side-encryption-kms-key-id: KMS master key. If this header is not provided, the default master key will be used. x-obs-sse-kms-key-project-id: ID of the project that the KMS master key belongs to
	Uploading Objects - POST
	Initiating a Multipart Upload
	Copying Objects

You can configure a bucket policy to limit the server-side encryption for a specific bucket to a specified method. For example, if you want people to use PUT to upload objects to bucket ExampleBucket and encrypt them with SSE-KMS, you can use the following bucket policy to deny any upload requests that do not contain the x-obs-server-side-encryption:"kms" header:

     
      
        
        
          {
    "Statement": [
        {
            "Sid": "DenyUnEncryptedObjectUploads",
            "Effect": "Deny",
            "Principal": "*",
            "Action": "PutObject",
            "Resource": "ExampleBucket/*",
            "Condition": {
                "StringNotEquals": {
                    "x-obs-server-side-encryption": "kms"
                }
            }
        }
    ]
}

         

       

     
    

SSE-OBS

SSE-OBS uses a data key derived from the OBS root key to encrypt and decrypt data. APIs related to SSE-OBS encryption

**Table 4** APIs related to SSE-OBS encryption
Resource	API	Header
Bucket	Creating a Bucket	x-obs-server-side-encryption: Encryption method of a bucket
Bucket	Configuring Bucket Encryption	The encryption configuration is in the body. For details, see Configuring Bucket Encryption.
Object	Uploading Objects - PUT	x-obs-server-side-encryption: Encryption method of a bucket
	Uploading Objects - POST
	Initiating a Multipart Upload
	Copying Objects

You can configure a bucket policy to restrict the request headers for a specified bucket. For example, if you require that object upload requests do not contain header x-obs-server-side-encryption:"AES256", you can use the following bucket policy:

     
      
        
        
          { 
    "Statement": [ 
        { 
            "Sid": "DenyUnEncryptedObjectUploads", 
            "Effect": "Deny", 
            "Principal": "*", 
            "Action": "PutObject", 
            "Resource": "YourBucket/*", 
            "Condition": { 
                "StringNotEquals": { 
                    "x-obs-server-side-encryption": "AES256" 
                } 
            } 
        } 
    ] 
}

         

       

     
    

SSE-C

With SSE-C, OBS uses the keys and MD5 values provided by customers for server-side encryption.

**Table 5** APIs that support SSE-C encryption
Resource	API	Header
Object level	Uploading Objects - PUT	x-obs-server-side-encryption-customer-algorithm: Algorithm used to encrypt an object x-obs-server-side-encryption-customer-key: Key used to encrypt an object. The header value is a 256-bit, base64-encoded key. x-obs-server-side-encryption-customer-key-MD5: MD5 value of the key used for encrypting an object
	Uploading Objects - POST
	Initiating a Multipart Upload
	Multipart Upload
	Querying Object Metadata
	Downloading Objects
	Uploading a Part of an Object - Copy	If the source part or object is not encrypted but you want to encrypt their copy, use the following three headers: x-obs-server-side-encryption-customer-algorithm: Algorithm used to encrypt an object x-obs-server-side-encryption-customer-key: Key used to encrypt an object. The header value is a 256-bit, base64-encoded key. x-obs-server-side-encryption-customer-key-MD5: MD5 value of the key used for encrypting an object If the source part or object has been encrypted and their copy also requires encryption, use the following headers to decrypt the source: x-obs-copy-source-server-side-encryption-customer-algorithm: Algorithm used to decrypt the source object x-obs-copy-source-server-side-encryption-customer-key: Key used to decrypt the source object. The header value is a 256-bit, base64-encoded key. x-obs-copy-source-server-side-encryption-customer-key-MD5: MD5 value of the key used for decrypting the source object
	Copying Objects

Enabling and Configuring Server-Side Encryption for a Bucket

You can use OBS Console, APIs, or SDKs to configure Server-Side Encryption for a bucket.

Using OBS Console

The following describes how to enable server-side encryption for an existing bucket. For details about how to enable server-side encryption when creating a bucket, see Creating a Bucket.

In the navigation pane of OBS Console, choose Object Storage.
In the bucket list, click the bucket you want to operate. The Objects page is displayed.
In the navigation pane, choose Overview.
In the Basic Configurations area, click Server-Side Encryption. The Server-Side Encryption dialog box is displayed.
Choose SSE-KMS or SSE-OBS.

Choose SSE-KMS.
- You can choose Default to use the default key in the current region to encrypt the objects you upload to the bucket. If you do not have a default key, OBS automatically creates one the first time you upload an object.
- You can also choose Custom to use a custom key for encryption. If there is no custom key available, click View KMS Keys to create one.
- You can also select Shared Key to enter a shared key ID. The key shared by other users will be used to encrypt your objects. For details about how to obtain a shared key ID, see Viewing a CMK.
  
  A shared key from a project or a subproject can be configured here. However, if a shared key from a subproject is specified, the owner of the shared key cannot access objects encrypted with that key, but the bucket owner can.
Figure 3 Choosing SSE-KMS for a bucket

When SSE-OBS is chosen, the keys created and managed by OBS are used for encryption.

Figure 4 Choosing SSE-OBS for a bucket
Click OK.

Using APIs

SSE-KMS

SSE-C

Configuring Bucket Encryption

Using SDKs

Configuring Object-Level Server-Side Encryption

You can use OBS Console, APIs, or SDKs to encrypt objects to be uploaded.

Using OBS Console

In the navigation pane of OBS Console, choose Object Storage.
In the bucket list, click the bucket you want to operate. The Objects page is displayed.
Click Upload Object. The Upload Object dialog box is displayed.
Add the files to be uploaded.

Enable Inherit from bucket if your bucket has server-side encryption enabled and the objects in it need to inherit the encryption configuration of the bucket.

Figure 5 Inherit from bucket

If your bucket has server-side encryption disabled or it has server-side encryption enabled but you need to a different encryption configuration for its objects, you can select SSE-KMS or SSE-OBS based on service requirements. If SSE-KMS is selected, you need to select an encryption key type.

**Table 6** Parameters related to server-side encryption
Parameter	Value
Encryption Key Type	Default	The default key of the current region will be used to encrypt your objects. If there is no such a default key, OBS creates one the first time you upload an object.
	Custom	You can click View KMS Keys to switch to the Data Encryption Workshop (DEW) console to create a key. Then go back here to select the key from the drop-down list.
	Shared	Enter the shared key ID. Your uploaded object will be encrypted using the key shared by other users. For details about how to obtain a shared key ID, see Viewing a CMK.