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重新加密資料

本主題說明如何使用 Cloud Key Management Service 對稱金鑰重新加密資料。您可以調整這些非對稱金鑰範例。如果您懷疑存在未經授權使用金鑰的情況，應重新加密受該金鑰保護的資料，然後對之前的金鑰版本執行停用或安排刪除作業。

事前準備

這種情況需要符合下列條件。

您已經使用 Cloud KMS 加密資料。
您未停用、安排刪除或刪除用於加密的金鑰版本。您可以使用這個金鑰版本對已加密的資料進行解密。
您已經輪替金鑰。金鑰輪替會建立新的主要金鑰版本。您可以使用新的主要金鑰版本重新加密資料。

使用非對稱金鑰重新加密資料

本主題的範例說明如何使用對稱金鑰重新加密資料。使用對稱式金鑰時，Cloud KMS 會自動推斷要用於解密的金鑰版本。使用非對稱金鑰時，您必須指定金鑰版本。

按照 Google Cloud CLI 使用說明操作時，請務必加入 --version 旗標。
按照 API 使用說明操作時，請使用 CryptoKeyVersions，而非 CryptoKeys。如要進一步瞭解如何使用非對稱金鑰加密及解密資料，請參閱這篇文章。

使用非對稱金鑰重新加密資料的工作流程，與本主題所述的流程類似。

重新加密資料的工作流程

請按照下列步驟重新加密資料，並停用或安排刪除用於原始加密的金鑰版本。

使用之前的金鑰版本解密資料
使用新的主要金鑰版本重新加密資料
停用或安排刪除之前的金鑰版本

使用之前的金鑰版本解密資料

Cloud KMS 會自動使用正確的金鑰版本解密資料，前提是您尚未停用、安排刪除，或是刪除該金鑰版本。下列範例會說明如何解密資料。這裡使用的解密程式碼，與在加密與解密中使用的程式碼相同。

gcloud

如要在指令列上使用 Cloud KMS，請先安裝或升級至最新版 Google Cloud CLI。

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

更改下列內容：

KEY_NAME：要用於解密的金鑰名稱。
KEY_RING：金鑰所屬金鑰環的名稱。
LOCATION：包含金鑰環的 Cloud KMS 位置。
FILE_TO_DECRYPT：要解密檔案的路徑。
DECRYPTED_OUTPUT：您要儲存解密輸出內容的路徑。

如要瞭解所有旗標和可能的值，請執行含有 --help 旗標的指令。

C#

如要執行這段程式碼，請先設定 C# 開發環境，然後安裝 Cloud KMS C# SDK。


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

如要執行這段程式碼，請先設定 Go 開發環境，並安裝 Cloud KMS Go SDK。

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

如要執行這段程式碼，請先設定 Java 開發環境，然後安裝 Cloud KMS Java SDK。

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

如要執行這段程式碼，請先設定 Node.js 開發環境，並安裝 Cloud KMS Node.js SDK。

//
// 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

如要執行這段程式碼，請先瞭解如何在 Google Cloud 上使用 PHP，並安裝 Cloud KMS PHP SDK。

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

如要執行這段程式碼，請先設定 Python 開發環境，然後安裝 Cloud KMS Python SDK。

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

如要執行這段程式碼，請先設定 Ruby 開發環境，然後安裝 Cloud KMS Ruby SDK。

# 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

這些範例使用 curl 做為 HTTP 用戶端，示範如何使用 API。如要進一步瞭解存取控管，請參閱「存取 Cloud KMS API」。

以 JSON 格式從 Cloud KMS 傳回的解密文字採用 base64 編碼。

如要解密已加密資料，請提出 POST 要求，並提供適當的專案和金鑰資訊，然後在要求主體的 ciphertext 欄位中指定要解密的已加密文字 (也稱為密文)。

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\"}"