Azure Key Vault key client library for .NET

Azure Key Vault is a cloud service that provides secure storage of keys for encrypting your data. Multiple keys, and multiple versions of the same key, can be kept in the Key Vault. Cryptographic keys in Key Vault are represented as JSON Web Key (JWK) objects.

The Azure Key Vault keys library client supports RSA keys and Elliptic Curve (EC) keys, each with corresponding support in hardware security modules (HSM). It offers operations to create, retrieve, update, delete, purge, backup, restore and list the keys and its versions.

Source code | Package (NuGet) | API reference documentation | Product documentation | Samples

Getting started

Install the package

Install the Azure Key Vault Keys client library for .NET with NuGet:

Install-Package Azure.Security.KeyVault.Keys -IncludePrerelease

Prerequisites

• An Azure subscription.
• An existing Key Vault. If you need to create a Key Vault, you can use the Azure Portal or Azure CLI.

If you use the Azure CLI, replace <your-resource-group-name> and <your-key-vault-name> with your own, unique names:

az keyvault create --resource-group <your-resource-group-name> --name <your-key-vault-name>

Authenticate the client

In order to interact with the Key Vault service, you'll need to create an instance of the KeyClient class. You would need a vault url, which you may see as "DNS Name" in the portal, and client secret credentials (client id, client secret, tenant id) to instantiate a client object.

Client secret credential authentication is being used in this getting started section but you can find more ways to authenticate with Azure identity. To use the DefaultAzureCredential provider shown below, or other credential providers provided with the Azure SDK, you should install the Azure.Identity package:

Install-Package Azure.Identity

Create/Get credentials

Use the Azure CLI snippet below to create/get client secret credentials.

• Create a service principal and configure its access to Azure resources:

  az ad sp create-for-rbac -n <your-application-name> --skip-assignment
  

  Output:

  {
      "appId": "generated-app-ID",
      "displayName": "dummy-app-name",
      "name": "http://dummy-app-name",
      "password": "random-password",
      "tenant": "tenant-ID"
  }
  

• Use the returned credentials above to set AZURE_CLIENT_ID(appId), AZURE_CLIENT_SECRET(password) and AZURE_TENANT_ID(tenant) environment variables. The following example shows a way to do this in Powershell:

  $Env:AZURE_CLIENT_ID="generated-app-ID"
  $Env:AZURE_CLIENT_SECRET="random-password"
  $Env:AZURE_TENANT_ID="tenant-ID"
  

• Grant the above mentioned application authorization to perform key operations on the Key Vault:

  az keyvault set-policy --name <your-key-vault-name> --spn $AZURE_CLIENT_ID --key-permissions backup delete get list create encrypt decrypt update
  

  --key-permissions: Accepted values: backup, create, decrypt, delete, encrypt, get, import, list, purge, recover, restore, sign, unwrapKey, update, verify, wrapKey

• Use the above mentioned Key Vault name to retrieve details of your Vault which also contains your Key Vault URL:

  az keyvault show --name <your-key-vault-name> 
  

Create KeyClient

Once you've populated the AZURE_CLIENT_ID, AZURE_CLIENT_SECRET and AZURE_TENANT_ID environment variables and replaced your-vault-url with the above returned URI, you can create the KeyClient:

// Create a new key client using the default credential from Azure.Identity using environment variables previously set,
// including AZURE_CLIENT_ID, AZURE_CLIENT_SECRET, and AZURE_TENANT_ID.
var client = new KeyClient(vaultUri: new Uri(keyVaultUrl), credential: new DefaultAzureCredential());

// Create a new key using the key client.
KeyVaultKey key = client.CreateKey("key-name", KeyType.Rsa);

// Retrieve a key using the key client.
key = client.GetKey("key-name");

Create CryptographyClient

Once you've created a KeyVaultKey in the Key Vault, you can also create the CryptographyClient:

// Create a new certificate client using the default credential from Azure.Identity using environment variables previously set,
// including AZURE_CLIENT_ID, AZURE_CLIENT_SECRET, and AZURE_TENANT_ID.
var cryptoClient = new CryptographyClient(keyId: key.Id, credential: new DefaultAzureCredential());

Key concepts

KeyVaultKey

Azure Key Vault supports multiple key types and algorithms, and enables the use of hardware security modules (HSM) for high value keys.

KeyClient

A KeyClient providing both synchronous and asynchronous operations exists in the SDK allowing for selection of a client based on an application's use case. Once you've initialized a KeyClient, you can interact with the primary resource types in Key Vault.

Cryptography Client:

A CryptographyClient providing both synchronous and asynchronous operations exists in the SDK allowing for selection of a client based on an application's use case. Once you've initialized a CryptographyClient, you can use it to perform cryptographic operations with keys stored in Key Vault.

Examples

The Azure.Security.KeyVault.Keys package supports synchronous and asynchronous APIs.

The following section provides several code snippets using the client created above, covering some of the most common Azure Key Vault key service related tasks:

Async examples

• Create a key
• Retrieve a key
• Update an existing key
• Delete a key
• Delete and purge a key
• List keys
• Encrypt and Decrypt

Sync examples

• Create a key synchronously
• Delete a key synchronously

Create a key

Create a key to be stored in the Azure Key Vault. If a key with the same name already exists, then a new version of the key is created.

// Create a key. Note that you can specify the type of key
// i.e. Elliptic curve, Hardware Elliptic Curve, RSA
KeyVaultKey key = await client.CreateKeyAsync("key-name", KeyType.Rsa);

Console.WriteLine(key.Name);
Console.WriteLine(key.KeyType);

// Create a software RSA key
var rsaCreateKey = new CreateRsaKeyOptions("rsa-key-name", hardwareProtected: false);
KeyVaultKey rsaKey = await client.CreateRsaKeyAsync(rsaCreateKey);

Console.WriteLine(rsaKey.Name);
Console.WriteLine(rsaKey.KeyType);

// Create a hardware Elliptic Curve key
// Because only premium key vault supports HSM backed keys , please ensure your key vault
// SKU is premium when you set "hardwareProtected" value to true
var echsmkey = new CreateEcKeyOptions("ec-key-name", hardwareProtected: true);
KeyVaultKey ecKey = await client.CreateEcKeyAsync(echsmkey);

Console.WriteLine(ecKey.Name);
Console.WriteLine(ecKey.KeyType);

Retrieve a key

GetKeyAsync retrieves a key previously stored in the Key Vault.

KeyVaultKey key = await client.GetKeyAsync("key-name");

Console.WriteLine(key.Name);
Console.WriteLine(key.KeyType);

Update an existing key

UpdateKeyAsync updates a key previously stored in the Key Vault.

KeyVaultKey key = await client.CreateKeyAsync("key-name", KeyType.Rsa);

// You can specify additional application-specific metadata in the form of tags.
key.Properties.Tags["foo"] = "updated tag";

KeyVaultKey updatedKey = await client.UpdateKeyPropertiesAsync(key.Properties);

Console.WriteLine(updatedKey.Name);
Console.WriteLine(updatedKey.Properties.Version);
Console.WriteLine(updatedKey.Properties.UpdatedOn);

Delete a key

StartDeleteKeyAsync starts a long-running operation to delete a key previously stored in the Key Vault. You can retrieve the key immediately without waiting for the operation to complete. When soft-delete is not enabled for the Key Vault, this operation permanently deletes the key.

DeleteKeyOperation operation = await client.StartDeleteKeyAsync("key-name");

DeletedKey key = operation.Value;
Console.WriteLine(key.Name);
Console.WriteLine(key.DeletedOn);

Delete and purge a key

You will need to wait for the long-running operation to complete before trying to purge or recover the key.

DeleteKeyOperation operation = await client.StartDeleteKeyAsync("key-name");

// You only need to wait for completion if you want to purge or recover the key.
await operation.WaitForCompletionAsync();

DeletedKey key = operation.Value;
await client.PurgeDeletedKeyAsync(key.Name);

List Keys

This example lists all the keys in the specified Key Vault.

AsyncPageable<KeyProperties> allKeys = client.GetPropertiesOfKeysAsync();

await foreach (KeyProperties keyProperties in allKeys)
{
    Console.WriteLine(keyProperties.Name);
}

Encrypt and Decrypt

This example creates a CryptographyClient and uses it to encrypt and decrypt with a key in Key Vault.

byte[] plaintext = Encoding.UTF8.GetBytes("A single block of plaintext");

// encrypt the data using the algorithm RSAOAEP
EncryptResult encryptResult = await cryptoClient.EncryptAsync(EncryptionAlgorithm.RsaOaep, plaintext);

// decrypt the encrypted data.
DecryptResult decryptResult = await cryptoClient.DecryptAsync(EncryptionAlgorithm.RsaOaep, encryptResult.Ciphertext);

Create a key synchronously

Synchronous APIs are identical to their asynchronous counterparts, but without the typical "Async" suffix for asynchronous methods.

// Create a key of any type
KeyVaultKey key = client.CreateKey("key-name", KeyType.Rsa);

Console.WriteLine(key.Name);
Console.WriteLine(key.KeyType);

// Create a software RSA key
var rsaCreateKey = new CreateRsaKeyOptions("rsa-key-name", hardwareProtected: false);
KeyVaultKey rsaKey = client.CreateRsaKey(rsaCreateKey);

Console.WriteLine(rsaKey.Name);
Console.WriteLine(rsaKey.KeyType);

// Create a hardware Elliptic Curve key
// Because only premium key vault supports HSM backed keys , please ensure your key vault
// SKU is premium when you set "hardwareProtected" value to true
var echsmkey = new CreateEcKeyOptions("ec-key-name", hardwareProtected: true);
KeyVaultKey ecKey = client.CreateEcKey(echsmkey);

Console.WriteLine(ecKey.Name);
Console.WriteLine(ecKey.KeyType);

Delete a key synchronously

When deleting a key synchronously before you purge it, you need to call UpdateStatus on the returned operation periodically. You could do this in a loop as shown in the example, or periodically within other operations in your program.

DeleteKeyOperation operation = client.StartDeleteKey("key-name");

while (!operation.HasCompleted)
{
    Thread.Sleep(2000);

    operation.UpdateStatus();
}

DeletedKey key = operation.Value;
client.PurgeDeletedKey(key.Name);

Troubleshooting

General

When you interact with the Azure Key Vault key client library using the .NET SDK, errors returned by the service correspond to the same HTTP status codes returned for REST API requests.

For example, if you try to retrieve a key that doesn't exist in your Key Vault, a 404 error is returned, indicating "Not Found".

try
{
    KeyVaultKey key = await client.GetKeyAsync("some_key");
}
catch (RequestFailedException ex)
{
    Console.WriteLine(ex.ToString());
}

You will notice that additional information is logged, like the client request ID of the operation.

Message:
    Azure.RequestFailedException : Service request failed.
    Status: 404 (Not Found)
Content:
    {"error":{"code":"KeyNotFound","message":"Key not found: some_key"}}

Headers:
    Cache-Control: no-cache
    Pragma: no-cache
    Server: Microsoft-IIS/10.0
    x-ms-keyvault-region: westus
    x-ms-request-id: 625f870e-10ea-41e5-8380-282e5cf768f2
    x-ms-keyvault-service-version: 1.1.0.866
    x-ms-keyvault-network-info: addr=131.107.174.199;act_addr_fam=InterNetwork;
    X-AspNet-Version: 4.0.30319
    X-Powered-By: ASP.NET
    Strict-Transport-Security: max-age=31536000;includeSubDomains
    X-Content-Type-Options: nosniff
    Date: Tue, 18 Jun 2019 16:02:11 GMT
    Content-Length: 75
    Content-Type: application/json; charset=utf-8
    Expires: -1

Next steps

Several Key Vault key client library samples are available to you in this GitHub repository. These samples provide example code for additional scenarios commonly encountered while working with Key Vault:

• HelloWorld.cs and HelloWorldAsync.cs - for working with Azure Key Vault, including:

  • Create a key
  • Get an existing key
  • Update an existing key
  • Delete a key

• BackupAndRestore.cs and BackupAndRestoreAsync.cs - Contains the code snippets working with Key Vault keys, including:

  • Backup and recover a key

• GetKeys.cs and GetKeysAsync.cs - Example code for working with Key Vault keys, including:

  • Create keys
  • List all keys in the Key Vault
  • Update keys in the Key Vault
  • List versions of a specified key
  • Delete keys from the Key Vault
  • List deleted keys in the Key Vault

• EncryptDecrypt.cs and EncryptDecryptAsync.cs - Example code for performing cryptographic operations with Key Vault keys, including:

  • Encrypt and Decrypt data with the CryptographyClient

• SignVerify.cs and SignVerifyAsync.cs - Example code for working with Key Vault keys, including:

  • Sign a precalculated digest and verify the signature with Sign and Verify
  • Sign raw data and verify the signature with SignData and VerifyData

• WrapUnwrap.cs and WrapUnwrapAsync.cs - Example code for working with Key Vault keys, including:

  • Wrap and Unwrap a symmetric key

Additional Documentation

• For more extensive documentation on Azure Key Vault, see the API reference documentation.
• For Secrets client library see Secrets client library.
• For Certificates client library see Certificates client library.

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.microsoft.com.

When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.