Get the public key for an asymmetric key

Get the public key for an asymmetric key.

Explore further

For detailed documentation that includes this code sample, see the following:

• Create a key
• Retrieve a public key

Code sample

C#

To learn how to install and use the client library for Cloud KMS, see Cloud KMS client libraries.

To authenticate to Cloud KMS, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

using Google.Cloud.Kms.V1;

public class GetPublicKeySample
{
    public PublicKey GetPublicKey(string projectId = "my-project", string locationId = "us-east1", string keyRingId = "my-key-ring", string keyId = "my-key", string keyVersionId = "123")
    {
        // Create the client.
        KeyManagementServiceClient client = KeyManagementServiceClient.Create();

        // Build the key version name.
        CryptoKeyVersionName keyVersionName = new CryptoKeyVersionName(projectId, locationId, keyRingId, keyId, keyVersionId);

        // Call the API.
        PublicKey result = client.GetPublicKey(keyVersionName);

        // Return the ciphertext.
        return result;
    }
}

Go

To learn how to install and use the client library for Cloud KMS, see Cloud KMS client libraries.

To authenticate to Cloud KMS, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import (
	"context"
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"hash/crc32"
	"io"

	kms "cloud.google.com/go/kms/apiv1"
	"cloud.google.com/go/kms/apiv1/kmspb"
)

// getPublicKey retrieves the public key from an asymmetric key pair on
// Cloud KMS.
func getPublicKey(w io.Writer, name string) error {
	// name := "projects/my-project/locations/us-east1/keyRings/my-key-ring/cryptoKeys/my-key/cryptoKeyVersions/123"

	// 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()

	// Build the request.
	req := &kmspb.GetPublicKeyRequest{
		Name: name,
	}

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

	// The 'Pem' field is the raw string representation of the public key.
	// Convert 'Pem' into bytes for further processing.
	key := []byte(result.Pem)

	// 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
	crc32c := func(data []byte) uint32 {
		t := crc32.MakeTable(crc32.Castagnoli)
		return crc32.Checksum(data, t)
	}
	if int64(crc32c(key)) != result.PemCrc32C.Value {
		return fmt.Errorf("getPublicKey: response corrupted in-transit")
	}

	// Optional - parse the public key. This transforms the string key into a Go
	// PublicKey.
	block, _ := pem.Decode(key)
	publicKey, err := x509.ParsePKIXPublicKey(block.Bytes)
	if err != nil {
		return fmt.Errorf("failed to parse public key: %w", err)
	}
	fmt.Fprintf(w, "Retrieved public key: %v\n", publicKey)
	return nil
}

Java

To learn how to install and use the client library for Cloud KMS, see Cloud KMS client libraries.

To authenticate to Cloud KMS, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import com.google.cloud.kms.v1.CryptoKeyVersionName;
import com.google.cloud.kms.v1.KeyManagementServiceClient;
import com.google.cloud.kms.v1.PublicKey;
import java.io.IOException;
import java.security.GeneralSecurityException;

public class GetPublicKey {

  public void getPublicKey() throws IOException, GeneralSecurityException {
    // 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 keyVersionId = "123";
    getPublicKey(projectId, locationId, keyRingId, keyId, keyVersionId);
  }

  // Get the public key associated with an asymmetric key.
  public void getPublicKey(
      String projectId, String locationId, String keyRingId, String keyId, String keyVersionId)
      throws IOException, GeneralSecurityException {
    // 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.
      CryptoKeyVersionName keyVersionName =
          CryptoKeyVersionName.of(projectId, locationId, keyRingId, keyId, keyVersionId);

      // Get the public key.
      PublicKey publicKey = client.getPublicKey(keyVersionName);
      System.out.printf("Public key: %s%n", publicKey.getPem());
    }
  }
}

Node.js

To learn how to install and use the client library for Cloud KMS, see Cloud KMS client libraries.

To authenticate to Cloud KMS, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

//
// 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';

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

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

// Build the key version name
const versionName = client.cryptoKeyVersionPath(
  projectId,
  locationId,
  keyRingId,
  keyId,
  versionId
);

async function getPublicKey() {
  const [publicKey] = await client.getPublicKey({
    name: versionName,
  });

  // Optional, but recommended: perform integrity verification on publicKey.
  // For more details on ensuring E2E in-transit integrity to and from Cloud KMS visit:
  // https://cloud.google.com/kms/docs/data-integrity-guidelines
  const crc32c = require('fast-crc32c');
  if (publicKey.name !== versionName) {
    throw new Error('GetPublicKey: request corrupted in-transit');
  }
  if (crc32c.calculate(publicKey.pem) !== Number(publicKey.pemCrc32c.value)) {
    throw new Error('GetPublicKey: response corrupted in-transit');
  }

  console.log(`Public key pem: ${publicKey.pem}`);

  return publicKey;
}

return getPublicKey();

PHP

To learn how to install and use the client library for Cloud KMS, see Cloud KMS client libraries.

To authenticate to Cloud KMS, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

use Google\Cloud\Kms\V1\Client\KeyManagementServiceClient;
use Google\Cloud\Kms\V1\GetPublicKeyRequest;

function get_public_key(
    string $projectId = 'my-project',
    string $locationId = 'us-east1',
    string $keyRingId = 'my-key-ring',
    string $keyId = 'my-key',
    string $versionId = '123'
) {
    // Create the Cloud KMS client.
    $client = new KeyManagementServiceClient();

    // Build the key version name.
    $keyVersionName = $client->cryptoKeyVersionName($projectId, $locationId, $keyRingId, $keyId, $versionId);

    // Call the API.
    $getPublicKeyRequest = (new GetPublicKeyRequest())
        ->setName($keyVersionName);
    $publicKey = $client->getPublicKey($getPublicKeyRequest);
    printf('Public key: %s' . PHP_EOL, $publicKey->getPem());

    return $publicKey;
}

Python

To learn how to install and use the client library for Cloud KMS, see Cloud KMS client libraries.

To authenticate to Cloud KMS, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

from google.cloud import kms


def get_public_key(
    project_id: str, location_id: str, key_ring_id: str, key_id: str, version_id: str
) -> kms.PublicKey:
    """
    Get the public key for an asymmetric 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').
        version_id (string): ID of the key to use (e.g. '1').

    Returns:
        PublicKey: Cloud KMS public key response.

    """

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

    # Build the key version name.
    key_version_name = client.crypto_key_version_path(
        project_id, location_id, key_ring_id, key_id, version_id
    )

    # Call the API.
    public_key = client.get_public_key(request={"name": key_version_name})

    # Optional, but recommended: perform integrity verification on public_key.
    # 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 public_key.name == key_version_name:
        raise Exception("The request sent to the server was corrupted in-transit.")
    # See crc32c() function defined below.
    if not public_key.pem_crc32c == crc32c(public_key.pem.encode("utf-8")):
        raise Exception(
            "The response received from the server was corrupted in-transit."
        )
    # End integrity verification

    print(f"Public key: {public_key.pem}")
    return public_key


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 learn how to install and use the client library for Cloud KMS, see Cloud KMS client libraries.

To authenticate to Cloud KMS, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

# 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"
# version_id  = "123"

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

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

# Build the key version name.
key_version_name = client.crypto_key_version_path project:            project_id,
                                                  location:           location_id,
                                                  key_ring:           key_ring_id,
                                                  crypto_key:         key_id,
                                                  crypto_key_version: version_id

# Call the API.
public_key = client.get_public_key name: key_version_name
puts "Public key: #{public_key.pem}"

What's next

To search and filter code samples for other Google Cloud products, see the Google Cloud sample browser.