POST /#X-Amz-Target=TrentService.Decrypt
Decrypts ciphertext that was encrypted by a KMS key using any of the following operations:
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Encrypt
-
GenerateDataKey
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GenerateDataKeyPair
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GenerateDataKeyWithoutPlaintext
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GenerateDataKeyPairWithoutPlaintext
You can use this operation to decrypt ciphertext that was encrypted under a symmetric encryption KMS key or an asymmetric encryption KMS key. When the KMS key is asymmetric, you must specify the KMS key and the encryption algorithm that was used to encrypt the ciphertext. For information about asymmetric KMS keys, see Asymmetric KMS keys in the Key Management Service Developer Guide.
The Decrypt operation also decrypts ciphertext that was encrypted outside of KMS by the public key in an KMS asymmetric KMS key. However, it cannot decrypt symmetric 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.
If the ciphertext was encrypted under a symmetric encryption KMS key, the KeyId 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 KMS key is always recommended as a best practice. When you use the KeyId parameter to specify a KMS key, KMS only uses the KMS key you specify. If the ciphertext was encrypted under a different KMS key, the Decrypt operation fails. This practice ensures that you use the KMS key that you intend.
Whenever possible, use key policies to give users permission to call the Decrypt operation on a particular KMS key, instead of using &IAM; policies. Otherwise, you might create an &IAM; policy that gives the user Decrypt permission on all KMS keys. This user could decrypt ciphertext that was encrypted by KMS keys in other accounts if the key policy for the cross-account KMS key permits it. If you must use an IAM policy for Decrypt permissions, limit the user to particular KMS keys or particular trusted accounts. For details, see Best practices for IAM policies in the Key Management Service Developer Guide.
Applications in Amazon Web Services Nitro Enclaves can call this operation by using the Amazon Web Services Nitro Enclaves Development Kit. For information about the supporting parameters, see How Amazon Web Services Nitro Enclaves use KMS in the Key Management Service Developer Guide.
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. If you use the KeyId parameter to identify a KMS key in a different Amazon Web Services account, specify the key ARN or the alias ARN of the KMS key.
Required permissions: kms:Decrypt (key policy)
Related operations:
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Encrypt
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GenerateDataKey
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GenerateDataKeyPair
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ReEncrypt
Servers
- https://kms.{region}.amazonaws.com
- https://kms.{region}.amazonaws.com.cn
Request headers
| Name | Type | Required | Description |
|---|---|---|---|
X-Amz-Content-Sha256 |
String | No | |
X-Amz-Credential |
String | No | |
X-Amz-Target |
String | Yes |
Valid values:
|
Content-Type |
String | Yes |
The media type of the request body.
Default value: "application/json" |
X-Amz-Date |
String | No | |
X-Amz-Algorithm |
String | No | |
X-Amz-SignedHeaders |
String | No | |
X-Amz-Security-Token |
String | No | |
X-Amz-Signature |
String | No |
Request body fields
| Name | Type | Required | Description |
|---|---|---|---|
GrantTokens[] |
Array | No |
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. |
EncryptionAlgorithm |
String | No |
Specifies the encryption algorithm that will be used to decrypt the ciphertext. Specify the same algorithm that was used to encrypt the data. If you specify a different algorithm, the This parameter is required only when the ciphertext was encrypted under an asymmetric KMS key. The default value, Valid values:
|
CiphertextBlob |
String | Yes |
Ciphertext to be decrypted. The blob includes metadata. |
KeyId |
String | No |
Specifies the KMS key that KMS uses to decrypt the ciphertext. Enter a key ID of the KMS key that was used to encrypt the ciphertext. If you identify a different KMS key, the 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 For example:
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. |
How to start integrating
- Add HTTP Task to your workflow definition.
- Search for the API you want to integrate with and click on the name.
- This loads the API reference documentation and prepares the Http request settings.
- Click Test request to test run your request to the API and see the API's response.