ReEncryptCommand

Decrypts ciphertext and then reencrypts it entirely within KMS. You can use this operation to change the KMS key under which data is encrypted, such as when you manually rotate  a KMS key or change the KMS key that protects a ciphertext. You can also use it to reencrypt ciphertext under the same KMS key, such as to change the encryption context  of a ciphertext.

The ReEncrypt operation can decrypt ciphertext that was encrypted by using a KMS key in an KMS operation, such as Encrypt or GenerateDataKey. It can also decrypt ciphertext that was encrypted by using the public key of an asymmetric KMS key  outside of KMS. However, it cannot decrypt ciphertext produced by other libraries, such as the Amazon Web Services Encryption SDK  or Amazon S3 client-side encryption . These libraries return a ciphertext format that is incompatible with KMS.

When you use the ReEncrypt operation, you need to provide information for the decrypt operation and the subsequent encrypt operation.

  • If your ciphertext was encrypted under an asymmetric KMS key, you must use the SourceKeyId parameter to identify the KMS key that encrypted the ciphertext. You must also supply the encryption algorithm that was used. This information is required to decrypt the data.

  • If your ciphertext was encrypted under a symmetric encryption KMS key, the SourceKeyId parameter is optional. KMS can get this information from metadata that it adds to the symmetric ciphertext blob. This feature adds durability to your implementation by ensuring that authorized users can decrypt ciphertext decades after it was encrypted, even if they've lost track of the key ID. However, specifying the source KMS key is always recommended as a best practice. When you use the SourceKeyId parameter to specify a KMS key, KMS uses only the KMS key you specify. If the ciphertext was encrypted under a different KMS key, the ReEncrypt operation fails. This practice ensures that you use the KMS key that you intend.

  • To reencrypt the data, you must use the DestinationKeyId parameter to specify the KMS key that re-encrypts the data after it is decrypted. If the destination KMS key is an asymmetric KMS key, you must also provide the encryption algorithm. The algorithm that you choose must be compatible with the KMS key.

    When you use an asymmetric KMS key to encrypt or reencrypt data, be sure to record the KMS key and encryption algorithm that you choose. You will be required to provide the same KMS key and encryption algorithm when you decrypt the data. If the KMS key and algorithm do not match the values used to encrypt the data, the decrypt operation fails.

    You are not required to supply the key ID and encryption algorithm when you decrypt with symmetric encryption KMS keys because KMS stores this information in the ciphertext blob. KMS cannot store metadata in ciphertext generated with asymmetric keys. The standard format for asymmetric key ciphertext does not include configurable fields.

The KMS key that you use for this operation must be in a compatible key state. For details, see Key states of KMS keys  in the Key Management Service Developer Guide.

Cross-account use: Yes. The source KMS key and destination KMS key can be in different Amazon Web Services accounts. Either or both KMS keys can be in a different account than the caller. To specify a KMS key in a different account, you must use its key ARN or alias ARN.

Required permissions:

To permit reencryption from or to a KMS key, include the "kms:ReEncrypt*" permission in your key policy . This permission is automatically included in the key policy when you use the console to create a KMS key. But you must include it manually when you create a KMS key programmatically or when you use the PutKeyPolicy operation to set a key policy.

Related operations:

  • Decrypt

  • Encrypt

  • GenerateDataKey

  • GenerateDataKeyPair

Eventual consistency: The KMS API follows an eventual consistency model. For more information, see KMS eventual consistency .

Example Syntax

Use a bare-bones client and the command you need to make an API call.

import { KMSClient, ReEncryptCommand } from "@aws-sdk/client-kms"; // ES Modules import
// const { KMSClient, ReEncryptCommand } = require("@aws-sdk/client-kms"); // CommonJS import
const client = new KMSClient(config);
const input = { // ReEncryptRequest
  CiphertextBlob: new Uint8Array(), // e.g. Buffer.from("") or new TextEncoder().encode("")   // required
  SourceEncryptionContext: { // EncryptionContextType
    "<keys>": "STRING_VALUE",
  },
  SourceKeyId: "STRING_VALUE",
  DestinationKeyId: "STRING_VALUE", // required
  DestinationEncryptionContext: {
    "<keys>": "STRING_VALUE",
  },
  SourceEncryptionAlgorithm: "SYMMETRIC_DEFAULT" || "RSAES_OAEP_SHA_1" || "RSAES_OAEP_SHA_256" || "SM2PKE",
  DestinationEncryptionAlgorithm: "SYMMETRIC_DEFAULT" || "RSAES_OAEP_SHA_1" || "RSAES_OAEP_SHA_256" || "SM2PKE",
  GrantTokens: [ // GrantTokenList
    "STRING_VALUE",
  ],
  DryRun: true || false,
};
const command = new ReEncryptCommand(input);
const response = await client.send(command);
// { // ReEncryptResponse
//   CiphertextBlob: new Uint8Array(),
//   SourceKeyId: "STRING_VALUE",
//   KeyId: "STRING_VALUE",
//   SourceEncryptionAlgorithm: "SYMMETRIC_DEFAULT" || "RSAES_OAEP_SHA_1" || "RSAES_OAEP_SHA_256" || "SM2PKE",
//   DestinationEncryptionAlgorithm: "SYMMETRIC_DEFAULT" || "RSAES_OAEP_SHA_1" || "RSAES_OAEP_SHA_256" || "SM2PKE",
// };

Example Usage

 There was an error loading the code editor. Retry

ReEncryptCommand Input

See ReEncryptCommandInput for more details

Parameter
Type
Description
CiphertextBlob
Required
Uint8Array | undefined

Ciphertext of the data to reencrypt.

DestinationKeyId
Required
string | undefined

A unique identifier for the KMS key that is used to reencrypt the data. Specify a symmetric encryption KMS key or an asymmetric KMS key with a KeyUsage value of ENCRYPT_DECRYPT. To find the KeyUsage value of a KMS key, use the DescribeKey operation.

To specify a KMS key, use its key ID, key ARN, alias name, or alias ARN. When using an alias name, prefix it with "alias/". To specify a KMS key in a different Amazon Web Services account, you must use the key ARN or alias ARN.

For example:

  • Key ID: 1234abcd-12ab-34cd-56ef-1234567890ab

  • Key ARN: arn:aws:kms:us-east-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab

  • Alias name: alias/ExampleAlias

  • Alias ARN: arn:aws:kms:us-east-2:111122223333:alias/ExampleAlias

To get the key ID and key ARN for a KMS key, use ListKeys or DescribeKey. To get the alias name and alias ARN, use ListAliases.

DestinationEncryptionAlgorithm
EncryptionAlgorithmSpec | undefined

Specifies the encryption algorithm that KMS will use to reecrypt the data after it has decrypted it. The default value, SYMMETRIC_DEFAULT, represents the encryption algorithm used for symmetric encryption KMS keys.

This parameter is required only when the destination KMS key is an asymmetric KMS key.

DestinationEncryptionContext
Record<string, string> | undefined

Specifies that encryption context to use when the reencrypting the data.

Do not include confidential or sensitive information in this field. This field may be displayed in plaintext in CloudTrail logs and other output.

A destination encryption context is valid only when the destination KMS key is a symmetric encryption KMS key. The standard ciphertext format for asymmetric KMS keys does not include fields for metadata.

An encryption context is a collection of non-secret key-value pairs that represent additional authenticated data. When you use an encryption context to encrypt data, you must specify the same (an exact case-sensitive match) encryption context to decrypt the data. An encryption context is supported only on operations with symmetric encryption KMS keys. On operations with symmetric encryption KMS keys, an encryption context is optional, but it is strongly recommended.

For more information, see Encryption context  in the Key Management Service Developer Guide.

DryRun
boolean | undefined

Checks if your request will succeed. DryRun is an optional parameter.

To learn more about how to use this parameter, see Testing your KMS API calls  in the Key Management Service Developer Guide.

GrantTokens
string[] | undefined

A list of grant tokens.

Use a grant token when your permission to call this operation comes from a new grant that has not yet achieved eventual consistency. For more information, see Grant token  and Using a grant token  in the Key Management Service Developer Guide.

SourceEncryptionAlgorithm
EncryptionAlgorithmSpec | undefined

Specifies the encryption algorithm that KMS will use to decrypt the ciphertext before it is reencrypted. The default value, SYMMETRIC_DEFAULT, represents the algorithm used for symmetric encryption KMS keys.

Specify the same algorithm that was used to encrypt the ciphertext. If you specify a different algorithm, the decrypt attempt fails.

This parameter is required only when the ciphertext was encrypted under an asymmetric KMS key.

SourceEncryptionContext
Record<string, string> | undefined

Specifies the encryption context to use to decrypt the ciphertext. Enter the same encryption context that was used to encrypt the ciphertext.

An encryption context is a collection of non-secret key-value pairs that represent additional authenticated data. When you use an encryption context to encrypt data, you must specify the same (an exact case-sensitive match) encryption context to decrypt the data. An encryption context is supported only on operations with symmetric encryption KMS keys. On operations with symmetric encryption KMS keys, an encryption context is optional, but it is strongly recommended.

For more information, see Encryption context  in the Key Management Service Developer Guide.

SourceKeyId
string | undefined

Specifies the KMS key that KMS will use to decrypt the ciphertext before it is re-encrypted.

Enter a key ID of the KMS key that was used to encrypt the ciphertext. If you identify a different KMS key, the ReEncrypt operation throws an IncorrectKeyException.

This parameter is required only when the ciphertext was encrypted under an asymmetric KMS key. If you used a symmetric encryption KMS key, KMS can get the KMS key from metadata that it adds to the symmetric ciphertext blob. However, it is always recommended as a best practice. This practice ensures that you use the KMS key that you intend.

To specify a KMS key, use its key ID, key ARN, alias name, or alias ARN. When using an alias name, prefix it with "alias/". To specify a KMS key in a different Amazon Web Services account, you must use the key ARN or alias ARN.

For example:

  • Key ID: 1234abcd-12ab-34cd-56ef-1234567890ab

  • Key ARN: arn:aws:kms:us-east-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab

  • Alias name: alias/ExampleAlias

  • Alias ARN: arn:aws:kms:us-east-2:111122223333:alias/ExampleAlias

To get the key ID and key ARN for a KMS key, use ListKeys or DescribeKey. To get the alias name and alias ARN, use ListAliases.

ReEncryptCommand Output

See ReEncryptCommandOutput for details

Parameter
Type
Description
$metadata
Required
ResponseMetadata
Metadata pertaining to this request.
CiphertextBlob
Uint8Array | undefined

The reencrypted data. When you use the HTTP API or the Amazon Web Services CLI, the value is Base64-encoded. Otherwise, it is not Base64-encoded.

DestinationEncryptionAlgorithm
EncryptionAlgorithmSpec | undefined

The encryption algorithm that was used to reencrypt the data.

KeyId
string | undefined

The Amazon Resource Name (key ARN ) of the KMS key that was used to reencrypt the data.

SourceEncryptionAlgorithm
EncryptionAlgorithmSpec | undefined

The encryption algorithm that was used to decrypt the ciphertext before it was reencrypted.

SourceKeyId
string | undefined

Unique identifier of the KMS key used to originally encrypt the data.

Throws

Name
Fault
Details
DependencyTimeoutException
server

The system timed out while trying to fulfill the request. You can retry the request.

DisabledException
client

The request was rejected because the specified KMS key is not enabled.

DryRunOperationException
client

The request was rejected because the DryRun parameter was specified.

IncorrectKeyException
client

The request was rejected because the specified KMS key cannot decrypt the data. The KeyId in a Decrypt request and the SourceKeyId in a ReEncrypt request must identify the same KMS key that was used to encrypt the ciphertext.

InvalidCiphertextException
client

From the Decrypt or ReEncrypt operation, the request was rejected because the specified ciphertext, or additional authenticated data incorporated into the ciphertext, such as the encryption context, is corrupted, missing, or otherwise invalid.

From the ImportKeyMaterial operation, the request was rejected because KMS could not decrypt the encrypted (wrapped) key material.

InvalidGrantTokenException
client

The request was rejected because the specified grant token is not valid.

InvalidKeyUsageException
client

The request was rejected for one of the following reasons:

  • The KeyUsage value of the KMS key is incompatible with the API operation.

  • The encryption algorithm or signing algorithm specified for the operation is incompatible with the type of key material in the KMS key (KeySpec).

For encrypting, decrypting, re-encrypting, and generating data keys, the KeyUsage must be ENCRYPT_DECRYPT. For signing and verifying messages, the KeyUsage must be SIGN_VERIFY. For generating and verifying message authentication codes (MACs), the KeyUsage must be GENERATE_VERIFY_MAC. For deriving key agreement secrets, the KeyUsage must be KEY_AGREEMENT. To find the KeyUsage of a KMS key, use the DescribeKey operation.

To find the encryption or signing algorithms supported for a particular KMS key, use the DescribeKey operation.

KeyUnavailableException
server

The request was rejected because the specified KMS key was not available. You can retry the request.

KMSInternalException
server

The request was rejected because an internal exception occurred. The request can be retried.

KMSInvalidStateException
client

The request was rejected because the state of the specified resource is not valid for this request.

This exceptions means one of the following:

  • The key state of the KMS key is not compatible with the operation.

    To find the key state, use the DescribeKey operation. For more information about which key states are compatible with each KMS operation, see Key states of KMS keys  in the Key Management Service Developer Guide .

  • For cryptographic operations on KMS keys in custom key stores, this exception represents a general failure with many possible causes. To identify the cause, see the error message that accompanies the exception.

NotFoundException
client

The request was rejected because the specified entity or resource could not be found.

KMSServiceException
Base exception class for all service exceptions from KMS service.