This page shows you how to use Cloud Key Management Service (Cloud KMS) to do the following
symmetric key operations:

- Encrypt text or binary content (plaintext) by using a Cloud KMS key.
- Decrypt ciphertext that was encrypted with a Cloud KMS key.

If you want to use an asymmetric key for encryption, see [Encrypting and
decrypting data with an asymmetric key](https://docs.cloud.google.com/kms/docs/encrypt-decrypt-rsa). To learn about raw
symmetric encryption, see [raw symmetric encryption](https://docs.cloud.google.com/kms/docs/raw-encryption.md.txt).

> [!NOTE]
> **Note:** For security reasons, the raw cryptographic key material represented by a Cloud KMS key can never be viewed or exported. It can only be used by an authorized user to encrypt or decrypt data when they invoke the Cloud KMS API.

## Before you begin

1. [Create a key ring](https://docs.cloud.google.com/kms/docs/create-key-ring.md.txt) and [create a key](https://docs.cloud.google.com/kms/docs/creating-keys).

2. Ensure the user that is calling the encrypt and decrypt methods has the
   `cloudkms.cryptoKeyVersions.useToEncrypt` and
   `cloudkms.cryptoKeyVersions.useToDecrypt` permissions on the key.

   One way to permit a user to encrypt or decrypt is to add the user to the
   `roles/cloudkms.cryptoKeyEncrypter`, `roles/cloudkms.cryptoKeyDecrypter`, or
   `roles/cloudkms.cryptoKeyEncrypterDecrypter` IAM roles for
   that key. The `roles/cloudkms.admin` role **does not**
   provide these two permissions. For more information, see
   [Permissions and Roles](https://docs.cloud.google.com/kms/docs/reference/permissions-and-roles.md.txt).

## Encrypt

### gcloud

To use Cloud KMS on the command line, first
[Install or upgrade to the latest version of Google Cloud CLI](https://docs.cloud.google.com/sdk/install).

```
gcloud kms encrypt \
    --key KEY_NAME \
    --keyring KEY_RING \
    --location LOCATION  \
    --plaintext-file FILE_TO_ENCRYPT \
    --ciphertext-file ENCRYPTED_OUTPUT
```

Replace the following:

- `KEY_NAME`: the name of the key that you want to use for encryption.
- `KEY_RING`: the name of the key ring that contains the key.
- `LOCATION`: the Cloud KMS location that contains the key ring.
- `FILE_TO_ENCRYPT`: the path to the file that you want to encrypt.
- `ENCRYPTED_OUTPUT`: the path where you want to save the encrypted output.

For information on all flags and possible values, run the command with the
`--help` flag.

### C#

To run this code, first [set up a C# development environment](https://docs.cloud.google.com/dotnet/docs/setup.md.txt) and
[install the Cloud KMS C# SDK](https://docs.cloud.google.com/kms/docs/reference/libraries.md.txt#client-libraries-install-csharp).

```c#

using Google.Cloud.Kms.V1;
using Google.Protobuf;
using System.Text;

public class EncryptSymmetricSample
{
    public byte[] EncryptSymmetric(
      string projectId = "my-project", string locationId = "us-east1", string keyRingId = "my-key-ring", string keyId = "my-key",
      string message = "Sample message")
    {
        // Create the client.
        KeyManagementServiceClient client = KeyManagementServiceClient.Create();

        // Build the key name.
        CryptoKeyName keyName = new CryptoKeyName(projectId, locationId, keyRingId, keyId);

        // Convert the message into bytes. Cryptographic plaintexts and
        // ciphertexts are always byte arrays.
        byte[] plaintext = Encoding.UTF8.GetBytes(message);

        // Call the API.
        EncryptResponse result = client.Encrypt(keyName, ByteString.CopyFrom(plaintext));

        // Return the ciphertext.
        return result.Ciphertext.ToByteArray();
    }
}
```

### Go

To run this code, first [set up a Go development environment](https://docs.cloud.google.com/go/docs/setup.md.txt) and
[install the Cloud KMS Go SDK](https://docs.cloud.google.com/kms/docs/reference/libraries.md.txt#client-libraries-install-go).

```go
import (
	"context"
	"fmt"
	"hash/crc32"
	"io"

	kms "cloud.google.com/go/kms/apiv1"
	"cloud.google.com/go/kms/apiv1/kmspb"
	"google.golang.org/protobuf/types/known/wrapperspb"
)

// encryptSymmetric encrypts the input plaintext with the specified symmetric
// Cloud KMS key.
func encryptSymmetric(w io.Writer, name string, message string) error {
	// name := "projects/my-project/locations/us-east1/keyRings/my-key-ring/cryptoKeys/my-key"
	// message := "Sample message"

	// Create the client.
	ctx := context.Background()
	client, err := kms.NewKeyManagementClient(ctx)
	if err != nil {
		return fmt.Errorf("failed to create kms client: %w", err)
	}
	defer client.Close()

	// Convert the message into bytes. Cryptographic plaintexts and
	// ciphertexts are always byte arrays.
	plaintext := []byte(message)

	// Optional but recommended: Compute plaintext's CRC32C.
	crc32c := func(data []byte) uint32 {
		t := crc32.MakeTable(crc32.Castagnoli)
		return crc32.Checksum(data, t)
	}
	plaintextCRC32C := crc32c(plaintext)

	// Build the request.
	req := &kmspb.EncryptRequest{
		Name:            name,
		Plaintext:       plaintext,
		PlaintextCrc32C: wrapperspb.Int64(int64(plaintextCRC32C)),
	}

	// Call the API.
	result, err := client.Encrypt(ctx, req)
	if err != nil {
		return fmt.Errorf("failed to encrypt: %w", err)
	}

	// Optional, but recommended: perform integrity verification on result.
	// For more details on ensuring E2E in-transit integrity to and from Cloud KMS visit:
	// https://cloud.google.com/kms/docs/data-integrity-guidelines
	if result.VerifiedPlaintextCrc32C == false {
		return fmt.Errorf("Encrypt: request corrupted in-transit")
	}
	if int64(crc32c(result.Ciphertext)) != result.CiphertextCrc32C.Value {
		return fmt.Errorf("Encrypt: response corrupted in-transit")
	}

	fmt.Fprintf(w, "Encrypted ciphertext: %s", result.Ciphertext)
	return nil
}
```

### Java

To run this code, first [set up a Java development environment](https://docs.cloud.google.com/java/docs/setup.md.txt) and
[install the Cloud KMS Java SDK](https://docs.cloud.google.com/kms/docs/reference/libraries.md.txt#client-libraries-install-java).

```java
import com.google.cloud.kms.v1.CryptoKeyName;
import com.google.cloud.kms.v1.EncryptResponse;
import com.google.cloud.kms.v1.KeyManagementServiceClient;
import com.google.protobuf.ByteString;
import java.io.IOException;

public class EncryptSymmetric {

  public void encryptSymmetric() throws IOException {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "your-project-id";
    String locationId = "us-east1";
    String keyRingId = "my-key-ring";
    String keyId = "my-key";
    String plaintext = "Plaintext to encrypt";
    encryptSymmetric(projectId, locationId, keyRingId, keyId, plaintext);
  }

  // Encrypt data with a given key.
  public void encryptSymmetric(
      String projectId, String locationId, String keyRingId, String keyId, String plaintext)
      throws IOException {
    // Initialize client that will be used to send requests. This client only
    // needs to be created once, and can be reused for multiple requests. After
    // completing all of your requests, call the "close" method on the client to
    // safely clean up any remaining background resources.
    try (KeyManagementServiceClient client = KeyManagementServiceClient.create()) {
      // Build the key version name from the project, location, key ring, key,
      // and key version.
      CryptoKeyName keyVersionName = CryptoKeyName.of(projectId, locationId, keyRingId, keyId);

      // Encrypt the plaintext.
      EncryptResponse response = client.encrypt(keyVersionName, ByteString.copyFromUtf8(plaintext));
      System.out.printf("Ciphertext: %s%n", response.getCiphertext().toStringUtf8());
    }
  }
}
```

### Node.js

To run this code, first [set up a Node.js development environment](https://docs.cloud.google.com/nodejs/docs/setup.md.txt) and
[install the Cloud KMS Node.js SDK](https://docs.cloud.google.com/kms/docs/reference/libraries.md.txt#client-libraries-install-nodejs).

```javascript
//
// TODO(developer): Uncomment these variables before running the sample.
//
// const projectId = 'my-project';
// const locationId = 'us-east1';
// const keyRingId = 'my-key-ring';
// const keyId = 'my-key';
// const plaintextBuffer = Buffer.from('...');

// Imports the Cloud KMS library
const {KeyManagementServiceClient} = require('@google-cloud/kms');

// Instantiates a client
const client = new KeyManagementServiceClient();

// Build the key name
const keyName = client.cryptoKeyPath(projectId, locationId, keyRingId, keyId);

// Optional, but recommended: compute plaintext's CRC32C.
const crc32c = require('fast-crc32c');
const plaintextCrc32c = crc32c.calculate(plaintextBuffer);

async function encryptSymmetric() {
  const [encryptResponse] = await client.encrypt({
    name: keyName,
    plaintext: plaintextBuffer,
    plaintextCrc32c: {
      value: plaintextCrc32c,
    },
  });

  const ciphertext = encryptResponse.ciphertext;

  // Optional, but recommended: perform integrity verification on encryptResponse.
  // For more details on ensuring E2E in-transit integrity to and from Cloud KMS visit:
  // https://cloud.google.com/kms/docs/data-integrity-guidelines
  if (!encryptResponse.verifiedPlaintextCrc32c) {
    throw new Error('Encrypt: request corrupted in-transit');
  }
  if (
    crc32c.calculate(ciphertext) !==
    Number(encryptResponse.ciphertextCrc32c.value)
  ) {
    throw new Error('Encrypt: response corrupted in-transit');
  }

  console.log(`Ciphertext: ${ciphertext.toString('base64')}`);
  return ciphertext;
}

return encryptSymmetric();
```

### PHP

To run this code, first learn about [using PHP on Google Cloud](https://docs.cloud.google.com/php/docs.md.txt) and
[install the Cloud KMS PHP SDK](https://docs.cloud.google.com/kms/docs/reference/libraries.md.txt#client-libraries-install-php).

```php
use Google\Cloud\Kms\V1\Client\KeyManagementServiceClient;
use Google\Cloud\Kms\V1\EncryptRequest;

function encrypt_symmetric(
    string $projectId = 'my-project',
    string $locationId = 'us-east1',
    string $keyRingId = 'my-key-ring',
    string $keyId = 'my-key',
    string $plaintext = '...'
) {
    // Create the Cloud KMS client.
    $client = new KeyManagementServiceClient();

    // Build the key name.
    $keyName = $client->cryptoKeyName($projectId, $locationId, $keyRingId, $keyId);

    // Call the API.
    $encryptRequest = (new EncryptRequest())
        ->setName($keyName)
        ->setPlaintext($plaintext);
    $encryptResponse = $client->encrypt($encryptRequest);
    printf('Ciphertext: %s' . PHP_EOL, $encryptResponse->getCiphertext());

    return $encryptResponse;
}
```

### Python

To run this code, first [set up a Python development environment](https://docs.cloud.google.com/python/docs/setup.md.txt) and
[install the Cloud KMS Python SDK](https://docs.cloud.google.com/kms/docs/reference/libraries.md.txt#client-libraries-install-python).

```python

# Import base64 for printing the ciphertext.
import base64

# Import the client library.
from google.cloud import kms


def encrypt_symmetric(
    project_id: str, location_id: str, key_ring_id: str, key_id: str, plaintext: str
) -> bytes:
    """
    Encrypt plaintext using a symmetric key.

    Args:
        project_id (string): Google Cloud project ID (e.g. 'my-project').
        location_id (string): Cloud KMS location (e.g. 'us-east1').
        key_ring_id (string): ID of the Cloud KMS key ring (e.g. 'my-key-ring').
        key_id (string): ID of the key to use (e.g. 'my-key').
        plaintext (string): message to encrypt

    Returns:
        bytes: Encrypted ciphertext.

    """

    # Convert the plaintext to bytes.
    plaintext_bytes = plaintext.encode("utf-8")

    # Optional, but recommended: compute plaintext's CRC32C.
    # See crc32c() function defined below.
    plaintext_crc32c = crc32c(plaintext_bytes)

    # Create the client.
    client = kms.KeyManagementServiceClient()

    # Build the key name.
    key_name = client.crypto_key_path(project_id, location_id, key_ring_id, key_id)

    # Call the API.
    encrypt_response = client.encrypt(
        request={
            "name": key_name,
            "plaintext": plaintext_bytes,
            "plaintext_crc32c": plaintext_crc32c,
        }
    )

    # Optional, but recommended: perform integrity verification on encrypt_response.
    # For more details on ensuring E2E in-transit integrity to and from Cloud KMS visit:
    # https://cloud.google.com/kms/docs/data-integrity-guidelines
    if not encrypt_response.verified_plaintext_crc32c:
        raise Exception("The request sent to the server was corrupted in-transit.")
    if not encrypt_response.ciphertext_crc32c == crc32c(encrypt_response.ciphertext):
        raise Exception(
            "The response received from the server was corrupted in-transit."
        )
    # End integrity verification

    print(f"Ciphertext: {base64.b64encode(encrypt_response.ciphertext)}")
    return encrypt_response


def crc32c(data: bytes) -> int:
    """
    Calculates the CRC32C checksum of the provided data.

    Args:
        data: the bytes over which the checksum should be calculated.

    Returns:
        An int representing the CRC32C checksum of the provided bytes.
    """
    import crcmod  # type: ignore

    crc32c_fun = crcmod.predefined.mkPredefinedCrcFun("crc-32c")
    return crc32c_fun(data)

```

### Ruby

To run this code, first [set up a Ruby development environment](https://docs.cloud.google.com/ruby/docs/setup.md.txt) and
[install the Cloud KMS Ruby SDK](https://docs.cloud.google.com/kms/docs/reference/libraries.md.txt#client-libraries-install-ruby).

```ruby
# TODO(developer): uncomment these values before running the sample.
# project_id  = "my-project"
# location_id = "us-east1"
# key_ring_id = "my-key-ring"
# key_id      = "my-key"
# plaintext  = "..."

# Require the library.
require "google/cloud/kms"

# Create the client.
client = Google::Cloud::Kms.key_management_service

# Build the parent key name.
key_name = client.crypto_key_path project:    project_id,
                                  location:   location_id,
                                  key_ring:   key_ring_id,
                                  crypto_key: key_id

# Call the API.
response = client.encrypt name: key_name, plaintext: plaintext
puts "Ciphertext: #{Base64.strict_encode64 response.ciphertext}"
```

### API


These examples use [curl](https://curl.haxx.se/) as an HTTP client
to demonstrate using the API. For more information about access control, see
[Accessing the Cloud KMS API](https://docs.cloud.google.com/kms/docs/accessing-the-api.md.txt).

When using JSON and the REST API, content must be base64 encoded before it can
be encrypted by Cloud KMS.


> [!TIP]
> **Tip** : You can base64-encode or decode data
> using the `base64` command on Linux or macOS, or the
> `Base64.exe` command on Windows. Programming and scripting
> languages typically include libraries for base64-encoding. For command-line
> examples, see [Base64 Encoding](https://docs.cloud.google.com/vision/docs/base64.md.txt) in the
> Cloud Vision API documentation.

<br />

To encrypt data, make a `POST` request and provide the appropriate project and
key information and specify the base64 encoded text to be encrypted in the
`plaintext` field of the request body.

```
curl "https://cloudkms.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/keyRings/KEY_RING/cryptoKeys/KEY_NAME:encrypt" \
  --request "POST" \
  --header "authorization: Bearer TOKEN" \
  --header "content-type: application/json" \
  --data "{\"plaintext\": \"PLAINTEXT_TO_ENCRYPT\"}"
```

Replace the following:

- `PROJECT_ID`: the ID of the project that contains the key ring and key that you want to use for encryption.
- `LOCATION`: the Cloud KMS location that contains the key ring.
- `KEY_RING`: the key ring that contains the key that you want to use for encryption.
- `KEY_NAME`: the name of the key that you want to use for encryption.
- `PLAINTEXT_TO_ENCRYPT`: the plaintext data that you want to encrypt. The plaintext must be base64 encoded before you call the `encrypt` method.

Here is an example payload with base64 encoded data:

```json
{
  "plaintext": "U3VwZXIgc2VjcmV0IHRleHQgdGhhdCBtdXN0IGJlIGVuY3J5cHRlZAo=",
}
```

<br />

## Decrypt

### gcloud

To use Cloud KMS on the command line, first
[Install or upgrade to the latest version of Google Cloud CLI](https://docs.cloud.google.com/sdk/install).

```
gcloud kms decrypt \
    --key KEY_NAME \
    --keyring KEY_RING \
    --location LOCATION  \
    --ciphertext-file FILE_TO_DECRYPT \
    --plaintext-file DECRYPTED_OUTPUT
```

Replace the following:

- `KEY_NAME`: the name of the key that you want to use for decryption.
- `KEY_RING`: the name of the key ring that contains the key.
- `LOCATION`: the Cloud KMS location that contains the key ring.
- `FILE_TO_DECRYPT`: the path to the file that you want to decrypt.
- `DECRYPTED_OUTPUT`: the path where you want to save the decrypted output.

For information on all flags and possible values, run the command with the
`--help` flag.

### C#

To run this code, first [set up a C# development environment](https://docs.cloud.google.com/dotnet/docs/setup.md.txt) and
[install the Cloud KMS C# SDK](https://docs.cloud.google.com/kms/docs/reference/libraries.md.txt#client-libraries-install-csharp).

```c#

using Google.Cloud.Kms.V1;
using Google.Protobuf;
using System.Text;

public class DecryptSymmetricSample
{
    public string DecryptSymmetric(
      string projectId = "my-project", string locationId = "us-east1", string keyRingId = "my-key-ring", string keyId = "my-key",
      byte[] ciphertext = null)
    {
        // Create the client.
        KeyManagementServiceClient client = KeyManagementServiceClient.Create();

        // Build the key name.
        CryptoKeyName keyName = new CryptoKeyName(projectId, locationId, keyRingId, keyId);

        // Call the API.
        DecryptResponse result = client.Decrypt(keyName, ByteString.CopyFrom(ciphertext));

        // Get the plaintext. Cryptographic plaintexts and ciphertexts are
        // always byte arrays.
        byte[] plaintext = result.Plaintext.ToByteArray();

        // Return the result.
        return Encoding.UTF8.GetString(plaintext);
    }
}
```

### Go

To run this code, first [set up a Go development environment](https://docs.cloud.google.com/go/docs/setup.md.txt) and
[install the Cloud KMS Go SDK](https://docs.cloud.google.com/kms/docs/reference/libraries.md.txt#client-libraries-install-go).

```go
import (
	"context"
	"fmt"
	"hash/crc32"
	"io"

	kms "cloud.google.com/go/kms/apiv1"
	"cloud.google.com/go/kms/apiv1/kmspb"
	"google.golang.org/protobuf/types/known/wrapperspb"
)

// decryptSymmetric will decrypt the input ciphertext bytes using the specified symmetric key.
func decryptSymmetric(w io.Writer, name string, ciphertext []byte) error {
	// name := "projects/my-project/locations/us-east1/keyRings/my-key-ring/cryptoKeys/my-key"
	// ciphertext := []byte("...")  // result of a symmetric encryption call

	// Create the client.
	ctx := context.Background()
	client, err := kms.NewKeyManagementClient(ctx)
	if err != nil {
		return fmt.Errorf("failed to create kms client: %w", err)
	}
	defer client.Close()

	// Optional, but recommended: Compute ciphertext's CRC32C.
	crc32c := func(data []byte) uint32 {
		t := crc32.MakeTable(crc32.Castagnoli)
		return crc32.Checksum(data, t)
	}
	ciphertextCRC32C := crc32c(ciphertext)

	// Build the request.
	req := &kmspb.DecryptRequest{
		Name:             name,
		Ciphertext:       ciphertext,
		CiphertextCrc32C: wrapperspb.Int64(int64(ciphertextCRC32C)),
	}

	// Call the API.
	result, err := client.Decrypt(ctx, req)
	if err != nil {
		return fmt.Errorf("failed to decrypt ciphertext: %w", err)
	}

	// Optional, but recommended: perform integrity verification on result.
	// For more details on ensuring E2E in-transit integrity to and from Cloud KMS visit:
	// https://cloud.google.com/kms/docs/data-integrity-guidelines
	if int64(crc32c(result.Plaintext)) != result.PlaintextCrc32C.Value {
		return fmt.Errorf("Decrypt: response corrupted in-transit")
	}

	fmt.Fprintf(w, "Decrypted plaintext: %s", result.Plaintext)
	return nil
}
```

### Java

To run this code, first [set up a Java development environment](https://docs.cloud.google.com/java/docs/setup.md.txt) and
[install the Cloud KMS Java SDK](https://docs.cloud.google.com/kms/docs/reference/libraries.md.txt#client-libraries-install-java).

```java
import com.google.cloud.kms.v1.CryptoKeyName;
import com.google.cloud.kms.v1.DecryptResponse;
import com.google.cloud.kms.v1.KeyManagementServiceClient;
import com.google.protobuf.ByteString;
import java.io.IOException;

public class DecryptSymmetric {

  public void decryptSymmetric() throws IOException {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "your-project-id";
    String locationId = "us-east1";
    String keyRingId = "my-key-ring";
    String keyId = "my-key";
    byte[] ciphertext = null;
    decryptSymmetric(projectId, locationId, keyRingId, keyId, ciphertext);
  }

  // Decrypt data that was encrypted using a symmetric key.
  public void decryptSymmetric(
      String projectId, String locationId, String keyRingId, String keyId, byte[] ciphertext)
      throws IOException {
    // Initialize client that will be used to send requests. This client only
    // needs to be created once, and can be reused for multiple requests. After
    // completing all of your requests, call the "close" method on the client to
    // safely clean up any remaining background resources.
    try (KeyManagementServiceClient client = KeyManagementServiceClient.create()) {
      // Build the key version name from the project, location, key ring, and
      // key.
      CryptoKeyName keyName = CryptoKeyName.of(projectId, locationId, keyRingId, keyId);

      // Decrypt the response.
      DecryptResponse response = client.decrypt(keyName, ByteString.copyFrom(ciphertext));
      System.out.printf("Plaintext: %s%n", response.getPlaintext().toStringUtf8());
    }
  }
}
```

### Node.js

To run this code, first [set up a Node.js development environment](https://docs.cloud.google.com/nodejs/docs/setup.md.txt) and
[install the Cloud KMS Node.js SDK](https://docs.cloud.google.com/kms/docs/reference/libraries.md.txt#client-libraries-install-nodejs).

```javascript
//
// TODO(developer): Uncomment these variables before running the sample.
//
// const projectId = 'my-project';
// const locationId = 'us-east1';
// const keyRingId = 'my-key-ring';
// const keyId = 'my-key';
// Ciphertext must be either a Buffer object or a base-64 encoded string
// const ciphertext = Buffer.from('...');

// Imports the Cloud KMS library
const {KeyManagementServiceClient} = require('@google-cloud/kms');

// Instantiates a client
const client = new KeyManagementServiceClient();

// Build the key name
const keyName = client.cryptoKeyPath(projectId, locationId, keyRingId, keyId);

// Optional, but recommended: compute ciphertext's CRC32C.
const crc32c = require('fast-crc32c');
const ciphertextCrc32c = crc32c.calculate(ciphertext);

async function decryptSymmetric() {
  const [decryptResponse] = await client.decrypt({
    name: keyName,
    ciphertext: ciphertext,
    ciphertextCrc32c: {
      value: ciphertextCrc32c,
    },
  });

  // Optional, but recommended: perform integrity verification on decryptResponse.
  // For more details on ensuring E2E in-transit integrity to and from Cloud KMS visit:
  // https://cloud.google.com/kms/docs/data-integrity-guidelines
  if (
    crc32c.calculate(decryptResponse.plaintext) !==
    Number(decryptResponse.plaintextCrc32c.value)
  ) {
    throw new Error('Decrypt: response corrupted in-transit');
  }

  const plaintext = decryptResponse.plaintext.toString();

  console.log(`Plaintext: ${plaintext}`);
  return plaintext;
}

return decryptSymmetric();
```

### PHP

To run this code, first learn about [using PHP on Google Cloud](https://docs.cloud.google.com/php/docs.md.txt) and
[install the Cloud KMS PHP SDK](https://docs.cloud.google.com/kms/docs/reference/libraries.md.txt#client-libraries-install-php).

```php
use Google\Cloud\Kms\V1\Client\KeyManagementServiceClient;
use Google\Cloud\Kms\V1\DecryptRequest;

function decrypt_symmetric(
    string $projectId = 'my-project',
    string $locationId = 'us-east1',
    string $keyRingId = 'my-key-ring',
    string $keyId = 'my-key',
    string $ciphertext = '...'
) {
    // Create the Cloud KMS client.
    $client = new KeyManagementServiceClient();

    // Build the key name.
    $keyName = $client->cryptoKeyName($projectId, $locationId, $keyRingId, $keyId);

    // Call the API.
    $decryptRequest = (new DecryptRequest())
        ->setName($keyName)
        ->setCiphertext($ciphertext);
    $decryptResponse = $client->decrypt($decryptRequest);
    printf('Plaintext: %s' . PHP_EOL, $decryptResponse->getPlaintext());

    return $decryptResponse;
}
```

### Python

To run this code, first [set up a Python development environment](https://docs.cloud.google.com/python/docs/setup.md.txt) and
[install the Cloud KMS Python SDK](https://docs.cloud.google.com/kms/docs/reference/libraries.md.txt#client-libraries-install-python).

```python
from google.cloud import kms


def decrypt_symmetric(
    project_id: str, location_id: str, key_ring_id: str, key_id: str, ciphertext: bytes
) -> kms.DecryptResponse:
    """
    Decrypt the ciphertext using the symmetric key

    Args:
        project_id (string): Google Cloud project ID (e.g. 'my-project').
        location_id (string): Cloud KMS location (e.g. 'us-east1').
        key_ring_id (string): ID of the Cloud KMS key ring (e.g. 'my-key-ring').
        key_id (string): ID of the key to use (e.g. 'my-key').
        ciphertext (bytes): Encrypted bytes to decrypt.

    Returns:
        DecryptResponse: Response including plaintext.

    """

    # Create the client.
    client = kms.KeyManagementServiceClient()

    # Build the key name.
    key_name = client.crypto_key_path(project_id, location_id, key_ring_id, key_id)

    # Optional, but recommended: compute ciphertext's CRC32C.
    # See crc32c() function defined below.
    ciphertext_crc32c = crc32c(ciphertext)

    # Call the API.
    decrypt_response = client.decrypt(
        request={
            "name": key_name,
            "ciphertext": ciphertext,
            "ciphertext_crc32c": ciphertext_crc32c,
        }
    )

    # Optional, but recommended: perform integrity verification on decrypt_response.
    # For more details on ensuring E2E in-transit integrity to and from Cloud KMS visit:
    # https://cloud.google.com/kms/docs/data-integrity-guidelines
    if not decrypt_response.plaintext_crc32c == crc32c(decrypt_response.plaintext):
        raise Exception(
            "The response received from the server was corrupted in-transit."
        )
    # End integrity verification

    print(f"Plaintext: {decrypt_response.plaintext!r}")
    return decrypt_response


def crc32c(data: bytes) -> int:
    """
    Calculates the CRC32C checksum of the provided data.
    Args:
        data: the bytes over which the checksum should be calculated.
    Returns:
        An int representing the CRC32C checksum of the provided bytes.
    """
    import crcmod  # type: ignore

    crc32c_fun = crcmod.predefined.mkPredefinedCrcFun("crc-32c")
    return crc32c_fun(data)

```

### Ruby

To run this code, first [set up a Ruby development environment](https://docs.cloud.google.com/ruby/docs/setup.md.txt) and
[install the Cloud KMS Ruby SDK](https://docs.cloud.google.com/kms/docs/reference/libraries.md.txt#client-libraries-install-ruby).

```ruby
# TODO(developer): uncomment these values before running the sample.
# project_id  = "my-project"
# location_id = "us-east1"
# key_ring_id = "my-key-ring"
# key_id      = "my-key"
# ciphertext  = "..."

# Require the library.
require "google/cloud/kms"

# Create the client.
client = Google::Cloud::Kms.key_management_service

# Build the parent key name.
key_name = client.crypto_key_path project:    project_id,
                                  location:   location_id,
                                  key_ring:   key_ring_id,
                                  crypto_key: key_id

# Call the API.
response = client.decrypt name: key_name, ciphertext: ciphertext
puts "Plaintext: #{response.plaintext}"
```

### API


These examples use [curl](https://curl.haxx.se/) as an HTTP client
to demonstrate using the API. For more information about access control, see
[Accessing the Cloud KMS API](https://docs.cloud.google.com/kms/docs/accessing-the-api.md.txt).

Decrypted text that is returned in the JSON from Cloud KMS is
base64 encoded.


> [!TIP]
> **Tip** : You can base64-encode or decode data
> using the `base64` command on Linux or macOS, or the
> `Base64.exe` command on Windows. Programming and scripting
> languages typically include libraries for base64-encoding. For command-line
> examples, see [Base64 Encoding](https://docs.cloud.google.com/vision/docs/base64.md.txt) in the
> Cloud Vision API documentation.

<br />

To decrypt encrypted data, make a `POST` request and provide the appropriate
project and key information and specify the encrypted text (also known as
*ciphertext* ) to be decrypted in the `ciphertext` field of the request body.

```
curl "https://cloudkms.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/keyRings/KEY_RING/cryptoKeys/KEY_NAME:decrypt" \
  --request "POST" \
  --header "authorization: Bearer TOKEN" \
  --header "content-type: application/json" \
  --data "{\"ciphertext\": \"ENCRYPTED_DATA\"}"
```

Replace the following:

- `PROJECT_ID`: the ID of the project that contains the key ring and key that you want to use for decryption.
- `LOCATION`: the Cloud KMS location that contains the key ring.
- `KEY_RING`: the key ring that contains the key that you want to use for decryption.
- `KEY_NAME`: the name of the key that you want to use for decryption.
- `ENCRYPTED_DATA`: the encrypted data that you want to decrypt.

Here is an example payload with base64 encoded data:

```json
{
  "ciphertext": "CiQAhMwwBo61cHas7dDgifrUFs5zNzBJ2uZtVFq4ZPEl6fUVT4kSmQ...",
}
```

<br />

## What's next

- Read more about [raw symmetric encryption](https://docs.cloud.google.com/kms/docs/raw-encryption.md.txt).
- Read more about [envelope encryption](https://docs.cloud.google.com/kms/docs/data-encryption-keys).
- Try the [Encrypt and decrypt data with Cloud KMS Codelab](https://codelabs.developers.google.com/codelabs/encrypt-and-decrypt-data-with-cloud-kms).