Azure.Security.KeyVault.Keys (.NET)

Client library for managing cryptographic keys in Azure Key Vault and Managed HSM.

Confirm vault/Managed HSM capability, tenant/RBAC, key name/version and lifecycle scope before changes. Symmetric Oct keys and hardware protection require a compatible service/tier; do not assume all examples work on an ordinary vault. Key operations must match the actual algorithm; narrow RSA Encrypt/Decrypt options cannot also sign/wrap without the corresponding allowed operations. Preserve version IDs with ciphertext/signatures and retain old keys until data no longer needs them. Backup files are sensitive and have service restore restrictions. RSA is for small payloads; use authenticated envelope encryption for bulk data.

Installation

dotnet add package Azure.Security.KeyVault.Keys
dotnet add package Azure.Identity

Example SDK version: 4.7.0; verify the supported package version/API for the target project.

Environment Variables

KEY_VAULT_NAME=<your-key-vault-name>
# Or full URI
AZURE_KEYVAULT_URL=https://<vault-name>.vault.azure.net

Client Hierarchy

KeyClient (key management)
├── CreateKey / CreateRsaKey / CreateEcKey
├── GetKey / GetKeys
├── UpdateKeyProperties
├── DeleteKey / PurgeDeletedKey
├── BackupKey / RestoreKey
└── GetCryptographyClient() → CryptographyClient

CryptographyClient (cryptographic operations)
├── Encrypt / Decrypt
├── WrapKey / UnwrapKey
├── Sign / Verify
└── SignData / VerifyData

KeyResolver (key resolution)
└── Resolve(keyId) → CryptographyClient

Authentication

DefaultAzureCredential (Recommended)

using Azure.Identity;
using Azure.Security.KeyVault.Keys;

var keyVaultName = Environment.GetEnvironmentVariable("KEY_VAULT_NAME");
var kvUri = $"https://{keyVaultName}.vault.azure.net";

var client = new KeyClient(new Uri(kvUri), new DefaultAzureCredential());

Service Principal

var credential = new ClientSecretCredential(
    tenantId: "<tenant-id>",
    clientId: "<client-id>",
    clientSecret: "<client-secret>");

var client = new KeyClient(new Uri(kvUri), credential);

Key Management

Create Keys

// Create RSA key
KeyVaultKey rsaKey = await client.CreateKeyAsync("my-rsa-key", KeyType.Rsa);
Console.WriteLine($"Created key: {rsaKey.Name}, Type: {rsaKey.KeyType}");

// Create RSA key with options
var rsaOptions = new CreateRsaKeyOptions("my-rsa-key-2048")
{
    KeySize = 2048,
    HardwareProtected = false, // true for HSM-backed
    ExpiresOn = DateTimeOffset.UtcNow.AddYears(1),
    NotBefore = DateTimeOffset.UtcNow,
    Enabled = true
};
rsaOptions.KeyOperations.Add(KeyOperation.Encrypt);
rsaOptions.KeyOperations.Add(KeyOperation.Decrypt);

KeyVaultKey rsaKey2 = await client.CreateRsaKeyAsync(rsaOptions);

// Create EC key
var ecOptions = new CreateEcKeyOptions("my-ec-key")
{
    CurveName = KeyCurveName.P256,
    HardwareProtected = true // HSM-backed
};
KeyVaultKey ecKey = await client.CreateEcKeyAsync(ecOptions);

// Create Oct (symmetric) key for wrap/unwrap
var octOptions = new CreateOctKeyOptions("my-oct-key")
{
    KeySize = 256,
    HardwareProtected = true
};
KeyVaultKey octKey = await client.CreateOctKeyAsync(octOptions);

Retrieve Keys

// Get specific key (latest version)
KeyVaultKey key = await client.GetKeyAsync("my-rsa-key");
Console.WriteLine($"Key ID: {key.Id}");
Console.WriteLine($"Key Type: {key.KeyType}");
Console.WriteLine($"Version: {key.Properties.Version}");

// Get specific version
KeyVaultKey keyVersion = await client.GetKeyAsync("my-rsa-key", "version-id");

// List all keys
await foreach (KeyProperties keyProps in client.GetPropertiesOfKeysAsync())
{
    Console.WriteLine($"Key: {keyProps.Name}, Enabled: {keyProps.Enabled}");
}

// List key versions
await foreach (KeyProperties version in client.GetPropertiesOfKeyVersionsAsync("my-rsa-key"))
{
    Console.WriteLine($"Version: {version.Version}, Created: {version.CreatedOn}");
}

Update Key Properties

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

key.Properties.ExpiresOn = DateTimeOffset.UtcNow.AddYears(2);
key.Properties.Tags["environment"] = "production";

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

Delete and Purge Keys

// Start delete operation
DeleteKeyOperation operation = await client.StartDeleteKeyAsync("my-rsa-key");

// Wait for deletion to complete (required before purge)
await operation.WaitForCompletionAsync();
Console.WriteLine($"Deleted key scheduled purge date: {operation.Value.ScheduledPurgeDate}");

// Purge is a separate irreversible operation, subject to purge protection.
// await client.PurgeDeletedKeyAsync("my-rsa-key");

// Or recover deleted key
RecoverDeletedKeyOperation recovery = await client.StartRecoverDeletedKeyAsync("my-rsa-key");
await recovery.WaitForCompletionAsync();
KeyVaultKey recoveredKey = recovery.Value;

Backup and Rest