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Decrypts ciphertext that was encrypted by a KMS key using any of the following operations:
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.
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
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
operation on a particular KMS key, instead of using &IAM; policies. Otherwise,
you might create an &IAM; policy that gives the user
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.
Decrypt also supports Amazon
Web Services Nitro Enclaves, which provide an isolated compute environment in
Amazon EC2. To call
Decrypt for a Nitro enclave, use the Amazon
Web Services Nitro Enclaves SDK or any Amazon Web Services SDK. Use the
parameter to provide the attestation document for the enclave. Instead of the plaintext
data, the response includes the plaintext data encrypted with the public key from
the attestation document (
CiphertextForRecipient).For information about
the interaction between KMS and Amazon Web Services Nitro Enclaves, see How
Amazon Web Services Nitro Enclaves uses KMS in the Key Management Service Developer
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)
This is an asynchronous operation using the standard naming convention for .NET 4.5 or higher. For .NET 3.5 the operation is implemented as a pair of methods using the standard naming convention of BeginDecrypt and EndDecrypt.
public virtual Task<DecryptResponse> DecryptAsync( DecryptRequest request, CancellationToken cancellationToken )
Container for the necessary parameters to execute the Decrypt service method.
A cancellation token that can be used by other objects or threads to receive notice of cancellation.
|DependencyTimeoutException||The system timed out while trying to fulfill the request. You can retry the request.|
|DisabledException||The request was rejected because the specified KMS key is not enabled.|
|DryRunOperationException||The request was rejected because the DryRun parameter was specified.|
|IncorrectKeyException||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||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||The request was rejected because the specified grant token is not valid.|
|InvalidKeyUsageException||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. 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||The request was rejected because the specified KMS key was not available. You can retry the request.|
|KMSInternalException||The request was rejected because an internal exception occurred. The request can be retried.|
|KMSInvalidStateException||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||The request was rejected because the specified entity or resource could not be found.|
.NET Core App:
Supported in: 3.1
Supported in: 2.0
Supported in: 4.5