Container for the parameters to the Decrypt operation. 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.
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.
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 Recipient
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
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:
Eventual consistency: The KMS API follows an eventual consistency model. For more information, see KMS eventual consistency.
Inheritance Hierarchy
Amazon.Runtime.AmazonWebServiceRequest
Amazon.KeyManagementService.AmazonKeyManagementServiceRequest
Amazon.KeyManagementService.Model.DecryptRequest
Namespace: Amazon.KeyManagementService.Model
Assembly: AWSSDK.KeyManagementService.dll
Version: 3.x.y.z
Syntax
public class DecryptRequest : AmazonKeyManagementServiceRequest IAmazonWebServiceRequest
The DecryptRequest type exposes the following members
Constructors
| Name | Description | |
|---|---|---|
|
DecryptRequest() |
Properties
| Name | Type | Description | |
|---|---|---|---|
|
|
CiphertextBlob | System.IO.MemoryStream |
Gets and sets the property CiphertextBlob. Ciphertext to be decrypted. The blob includes metadata. |
|
|
DryRun | System.Boolean |
Gets and sets the property DryRun.
Checks if your request will succeed. To learn more about how to use this parameter, see Testing your KMS API calls in the Key Management Service Developer Guide. |
|
|
EncryptionAlgorithm | Amazon.KeyManagementService.EncryptionAlgorithmSpec |
Gets and sets the property EncryptionAlgorithm.
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, |
|
|
EncryptionContext | System.Collections.Generic.Dictionary<System.String, System.String> |
Gets and sets the property EncryptionContext. Specifies the encryption context to use when decrypting the data. An encryption context is valid only for cryptographic operations with a symmetric encryption KMS key. The standard asymmetric encryption algorithms and HMAC algorithms that KMS uses do not support an encryption context. 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. |
|
|
GrantTokens | System.Collections.Generic.List<System.String> |
Gets and sets the property GrantTokens. 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. |
|
|
KeyId | System.String |
Gets and sets the property KeyId. 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. |
|
|
Recipient | Amazon.KeyManagementService.Model.RecipientInfo |
Gets and sets the property Recipient.
A signed attestation
document from an Amazon Web Services Nitro enclave and the encryption algorithm
to use with the enclave's public key. The only valid encryption algorithm is This parameter only supports attestation documents for Amazon Web Services Nitro Enclaves. To include this parameter, use the Amazon Web Services Nitro Enclaves SDK or any Amazon Web Services SDK.
When you use this parameter, instead of returning the plaintext data, KMS encrypts
the plaintext data with the public key in the attestation document, and returns the
resulting ciphertext in the 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 Guide. |
Examples
The following example decrypts data that was encrypted with a symmetric encryption KMS key. The KeyId is not required when decrypting with a symmetric encryption key, but it is a best practice.
To decrypt data with a symmetric encryption KMS key
var client = new AmazonKeyManagementServiceClient();
var response = client.Decrypt(new DecryptRequest
{
CiphertextBlob = new MemoryStream(<binary data>), // The encrypted data (ciphertext).
KeyId = "arn:aws:kms:us-west-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab" // A key identifier for the KMS key to use to decrypt the data.
});
string encryptionAlgorithm = response.EncryptionAlgorithm; // The encryption algorithm that was used to decrypt the ciphertext. SYMMETRIC_DEFAULT is the only valid value for symmetric encryption in AWS KMS.
string keyId = response.KeyId; // The Amazon Resource Name (ARN) of the KMS key that was used to decrypt the data.
MemoryStream plaintext = response.Plaintext; // The decrypted (plaintext) data.
The following example decrypts data that was encrypted with an asymmetric encryption KMS key. When the KMS encryption key is asymmetric, you must specify the KMS key ID and the encryption algorithm that was used to encrypt the data.
To decrypt data with an asymmetric encryption KMS key
var client = new AmazonKeyManagementServiceClient();
var response = client.Decrypt(new DecryptRequest
{
CiphertextBlob = new MemoryStream(<binary data>), // The encrypted data (ciphertext).
EncryptionAlgorithm = "RSAES_OAEP_SHA_256", // The encryption algorithm that was used to encrypt the data. This parameter is required to decrypt with an asymmetric KMS key.
KeyId = "0987dcba-09fe-87dc-65ba-ab0987654321" // A key identifier for the KMS key to use to decrypt the data. This parameter is required to decrypt with an asymmetric KMS key.
});
string encryptionAlgorithm = response.EncryptionAlgorithm; // The encryption algorithm that was used to decrypt the ciphertext.
string keyId = response.KeyId; // The Amazon Resource Name (ARN) of the KMS key that was used to decrypt the data.
MemoryStream plaintext = response.Plaintext; // The decrypted (plaintext) data.
The following Decrypt example includes the Recipient parameter with a signed attestation document from an AWS Nitro enclave. Instead of returning the decrypted data in plaintext (Plaintext), the operation returns the decrypted data encrypted by the public key from the attestation document (CiphertextForRecipient).
To decrypt data for a Nitro enclave
var client = new AmazonKeyManagementServiceClient();
var response = client.Decrypt(new DecryptRequest
{
CiphertextBlob = new MemoryStream(<binary data>), // The encrypted data. This ciphertext was encrypted with the KMS key
KeyId = "arn:aws:kms:us-west-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab", // The KMS key to use to decrypt the ciphertext
Recipient = new RecipientInfo {
AttestationDocument = new MemoryStream(<attestation document>),
KeyEncryptionAlgorithm = "RSAES_OAEP_SHA_256"
} // Specifies the attestation document from the Nitro enclave and the encryption algorithm to use with the public key from the attestation document
});
MemoryStream ciphertextForRecipient = response.CiphertextForRecipient; // The decrypted CiphertextBlob encrypted with the public key from the attestation document
string keyId = response.KeyId; // The KMS key that was used to decrypt the encrypted data (CiphertextBlob)
MemoryStream plaintext = response.Plaintext; // This field is null or empty
Version Information
.NET:
Supported in: 8.0 and newer, Core 3.1
.NET Standard:
Supported in: 2.0
.NET Framework:
Supported in: 4.5 and newer, 3.5