C# (CSharp) Amazon.KeyManagementService.Model Namespace

For more information about scheduling and canceling deletion of a CMK, see Deleting Customer Master Keys in the AWS Key Management Service Developer Guide.

The alias and the key it is mapped to must be in the same AWS account and the same region.

To map an alias to a different key, call UpdateAlias.

For more information about grants, see Grants in the AWS Key Management Service Developer Guide.

You can use a CMK to encrypt small amounts of data (4 KiB or less) directly, but CMKs are more commonly used to encrypt data encryption keys (DEKs), which are used to encrypt raw data. For more information about DEKs and the difference between CMKs and DEKs, see the following:

• The GenerateDataKey operation

• AWS Key Management Service Concepts in the AWS Key Management Service Developer Guide

• GenerateDataKey

• GenerateDataKeyWithoutPlaintext

• Encrypt

Note that if a caller has been granted access permissions to all keys (through, for example, IAM user policies that grant Decrypt permission on all resources), then ciphertext encrypted by using keys in other accounts where the key grants access to the caller can be decrypted. To remedy this, we recommend that you do not grant Decrypt access in an IAM user policy. Instead grant Decrypt access only in key policies. If you must grant Decrypt access in an IAM user policy, you should scope the resource to specific keys or to specific trusted accounts.

When the specified CMK is in the PendingDeletion state, this operation does not change the CMK's state. Otherwise, it changes the CMK's state to PendingImport.

After you delete key material, you can use ImportKeyMaterial to reimport the same key material into the CMK.

• You can encrypt up to 4 KB of arbitrary data such as an RSA key, a database password, or other sensitive customer information.

• If you are moving encrypted data from one region to another, you can use this API to encrypt in the new region the plaintext data key that was used to encrypt the data in the original region. This provides you with an encrypted copy of the data key that can be decrypted in the new region and used there to decrypt the encrypted data.

Unless you are moving encrypted data from one region to another, you don't use this function to encrypt a generated data key within a region. You retrieve data keys already encrypted by calling the GenerateDataKey or GenerateDataKeyWithoutPlaintext function. Data keys don't need to be encrypted again by calling Encrypt.

If you want to encrypt data locally in your application, you can use the GenerateDataKey function to return a plaintext data encryption key and a copy of the key encrypted under the customer master key (CMK) of your choosing.

You must specify the customer master key (CMK) under which to generate the data key. You must also specify the length of the data key using either the KeySpec or NumberOfBytes field. You must specify one field or the other, but not both. For common key lengths (128-bit and 256-bit symmetric keys), we recommend that you use KeySpec.

This operation returns a plaintext copy of the data key in the Plaintext field of the response, and an encrypted copy of the data key in the CiphertextBlob field. The data key is encrypted under the CMK specified in the KeyId field of the request.

We recommend that you use the following pattern to encrypt data locally in your application:

1. Use this operation (GenerateDataKey) to retrieve a data encryption key.

2. Use the plaintext data encryption key (returned in the Plaintext field of the response) to encrypt data locally, then erase the plaintext data key from memory.

3. Store the encrypted data key (returned in the CiphertextBlob field of the response) alongside the locally encrypted data.

To decrypt data locally:

1. Use the Decrypt operation to decrypt the encrypted data key into a plaintext copy of the data key.

2. Use the plaintext data key to decrypt data locally, then erase the plaintext data key from memory.

To return only an encrypted copy of the data key, use GenerateDataKeyWithoutPlaintext. To return an arbitrary unpredictable byte string, use GenerateRandom.

If you use the optional EncryptionContext field, you must store at least enough information to be able to reconstruct the full encryption context when you later send the ciphertext to the Decrypt operation. It is a good practice to choose an encryption context that you can reconstruct on the fly to better secure the ciphertext. For more information, see Encryption Context in the AWS Key Management Service Developer Guide.

This operation is useful in a system that has multiple components with different degrees of trust. For example, consider a system that stores encrypted data in containers. Each container stores the encrypted data and an encrypted copy of the data key. One component of the system, called the control plane, creates new containers. When it creates a new container, it uses this operation (GenerateDataKeyWithoutPlaintext) to get an encrypted data key and then stores it in the container. Later, a different component of the system, called the data plane, puts encrypted data into the containers. To do this, it passes the encrypted data key to the Decrypt operation, then uses the returned plaintext data key to encrypt data, and finally stores the encrypted data in the container. In this system, the control plane never sees the plaintext data key.

You must specify the key ID of the customer master key (CMK) into which you will import key material. This CMK's Origin must be EXTERNAL. You must also specify the wrapping algorithm and type of wrapping key (public key) that you will use to encrypt the key material.

This operation returns a public key and an import token. Use the public key to encrypt the key material. Store the import token to send with a subsequent ImportKeyMaterial request. The public key and import token from the same response must be used together. These items are valid for 24 hours, after which they cannot be used for a subsequent ImportKeyMaterial request. To retrieve new ones, send another GetParametersForImport request.

You can use this structure to allow the operations permitted by the grant only when a specified encryption context is present. For more information about encryption context, see Encryption Context in the AWS Key Management Service Developer Guide.

You must specify the key ID of the CMK to import the key material into. This CMK's Origin must be EXTERNAL. You must also send an import token and the encrypted key material. Send the import token that you received in the same GetParametersForImport response that contained the public key that you used to encrypt the key material. You must also specify whether the key material expires and if so, when. When the key material expires, AWS KMS deletes the key material and the CMK becomes unusable. To use the CMK again, you can reimport the same key material. If you set an expiration date, you can change it only by reimporting the same key material and specifying a new expiration date.

When this operation is successful, the specified CMK's key state changes to Enabled, and you can use the CMK.

After you successfully import key material into a CMK, you can reimport the same key material into that CMK, but you cannot import different key material.

A typical use is to list all grants that you are able to retire. To retire a grant, use RetireGrant.

For more information about key policies, see Key Policies in the AWS Key Management Service Developer Guide.

Unlike other operations, ReEncrypt is authorized twice, once as ReEncryptFrom on the source CMK and once as ReEncryptTo on the destination CMK. We recommend that you include the "kms:ReEncrypt*" permission in your key policies to permit reencryption from or to the CMK. This permission is automatically included in the key policy when you create a CMK through the console, but you must include it manually when you create a CMK programmatically or when you set a key policy with the PutKeyPolicy operation.

• The AWS account (root user) under which the grant was created

• The RetiringPrincipal, if present in the grant

• The GranteePrincipal, if RetireGrant is an operation specified in the grant

You must identify the grant to retire by its grant token or by a combination of the grant ID and the Amazon Resource Name (ARN) of the customer master key (CMK). A grant token is a unique variable-length base64-encoded string. A grant ID is a 64 character unique identifier of a grant. The CreateGrant operation returns both.

For more information about scheduling a CMK for deletion, see Deleting Customer Master Keys in the AWS Key Management Service Developer Guide.

An alias is not a property of a key. Therefore, an alias can be mapped to and unmapped from an existing key without changing the properties of the key.

An alias name can contain only alphanumeric characters, forward slashes (/), underscores (_), and dashes (-). An alias must start with the word "alias" followed by a forward slash (alias/). An alias that begins with "aws" after the forward slash (alias/aws...) is reserved by Amazon Web Services (AWS).

The alias and the key it is mapped to must be in the same AWS account and the same region.