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Derives a shared secret using a key agreement algorithm.
You must use an asymmetric NIST-recommended elliptic curve (ECC) or SM2 (China Regions
only) KMS key pair with a KeyUsage value of KEY_AGREEMENT to call DeriveSharedSecret.
DeriveSharedSecret uses the Elliptic Curve Cryptography Cofactor Diffie-Hellman Primitive (ECDH) to establish a key agreement between two peers by deriving a shared secret from their elliptic curve public-private key pairs. You can use the raw shared secret that DeriveSharedSecret returns to derive a symmetric key that can encrypt and decrypt data that is sent between the two peers, or that can generate and verify HMACs. KMS recommends that you follow NIST recommendations for key derivation when using the raw shared secret to derive a symmetric key.
The following workflow demonstrates how to establish key agreement over an insecure communication channel using DeriveSharedSecret.
Alice calls CreateKey to create an asymmetric KMS key pair with a KeyUsage
value of KEY_AGREEMENT.
The asymmetric KMS key must use a NIST-recommended elliptic curve (ECC) or SM2 (China Regions only) key spec.
Bob creates an elliptic curve key pair.
Bob can call CreateKey to create an asymmetric KMS key pair or generate a key pair outside of KMS. Bob's key pair must use the same NIST-recommended elliptic curve (ECC) or SM2 (China Regions ony) curve as Alice.
Alice and Bob exchange their public keys through an insecure communication channel (like the internet).
Use GetPublicKey to download the public key of your asymmetric KMS key pair.
KMS strongly recommends verifying that the public key you receive came from the expected party before using it to derive a shared secret.
Alice calls DeriveSharedSecret.
KMS uses the private key from the KMS key pair generated in Step 1, Bob's public key, and the Elliptic Curve Cryptography Cofactor Diffie-Hellman Primitive to derive the shared secret. The private key in your KMS key pair never leaves KMS unencrypted. DeriveSharedSecret returns the raw shared secret.
Bob uses the Elliptic Curve Cryptography Cofactor Diffie-Hellman Primitive to calculate the same raw secret using his private key and Alice's public key.
To derive a shared secret you must provide a key agreement algorithm, the private key of the caller's asymmetric NIST-recommended elliptic curve or SM2 (China Regions only) KMS key pair, and the public key from your peer's NIST-recommended elliptic curve or SM2 (China Regions only) key pair. The public key can be from another asymmetric KMS key pair or from a key pair generated outside of KMS, but both key pairs must be on the same elliptic curve.
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. To perform this operation with a KMS key in a different
Amazon Web Services account, specify the key ARN or alias ARN in the value of the
KeyId parameter.
Required permissions: kms:DeriveSharedSecret (key policy)
Related operations:
Eventual consistency: The KMS API follows an eventual consistency model. For more information, see KMS eventual consistency.
For .NET Core this operation is only available in asynchronous form. Please refer to DeriveSharedSecretAsync.
Namespace: Amazon.KeyManagementService
Assembly: AWSSDK.KeyManagementService.dll
Version: 3.x.y.z
public virtual DeriveSharedSecretResponse DeriveSharedSecret( DeriveSharedSecretRequest request )
Container for the necessary parameters to execute the DeriveSharedSecret service method.
| Exception | Condition |
|---|---|
| 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. |
| 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. 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 | 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. |
The following example derives a shared secret using a key agreement algorithm.
var client = new AmazonKeyManagementServiceClient();
var response = client.DeriveSharedSecret(new DeriveSharedSecretRequest
{
KeyAgreementAlgorithm = "ECDH", // The key agreement algorithm used to derive the shared secret. The only valid value is ECDH.
KeyId = "1234abcd-12ab-34cd-56ef-1234567890ab", // The key identifier for an asymmetric KMS key pair. The private key in the specified key pair is used to derive the shared secret.
PublicKey = new MemoryStream(MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAvH3Yj0wbkLEpUl95Cv1cJVjsVNSjwGq3tCLnzXfhVwVvmzGN8pYj3U8nKwgouaHbBWNJYjP5VutbbkKS4Kv4GojwZBJyHN17kmxo8yTjRmjR15SKIQ8cqRA2uaERMLnpztIXdZp232PQPbWGxDyXYJ0aJ5EFSag) // The public key in your peer's asymmetric key pair.
});
string keyAgreementAlgorithm = response.KeyAgreementAlgorithm; // The key agreement algorithm used to derive the shared secret.
string keyId = response.KeyId; // The asymmetric KMS key pair used to derive the shared secret.
string keyOrigin = response.KeyOrigin; // The source of the key material for the specified KMS key.
MemoryStream sharedSecret = response.SharedSecret; // The raw secret derived from the specified key agreement algorithm, private key in the asymmetric KMS key, and your peer's public key.
.NET Framework:
Supported in: 4.5 and newer, 3.5