管理金鑰

Tink 提供解決方案,可避免金鑰管理不當,這是風險的主要來源

建立及輪替金鑰

為您的用途選取基本體和金鑰類型後 (在先前的「我想...」部分),請使用您選擇的外部「金鑰管理系統 (KMS)」管理金鑰:

  1. 在 KMS 中建立金鑰加密金鑰 (KEK),保護您的金鑰。

  2. 從 KMS 擷取金鑰 URI 和金鑰憑證,然後傳遞至 Tink。

  3. 使用 Tink 的 API 或 Tinkey 產生加密金鑰集。加密金鑰後,您可以將金鑰儲存在任何位置。

  4. 輪替金鑰,避免過度重複使用金鑰,並從金鑰遭盜用的情況中復原。

如要匯出金鑰,請參閱「以程式輔助方式匯出金鑰材料」,瞭解如何安全地匯出金鑰。

步驟 1:在外部 KMS 中建立 KEK

在外部 KMS 中建立金鑰加密金鑰 (KEK)。KEK 會加密金鑰,為金鑰多添一層安全防護。

請參閱 KMS 專用說明文件,瞭解如何建立 KEK:

步驟 2:取得金鑰 URI 和憑證

您可以從 KMS 擷取金鑰 URI 和金鑰憑證。

取得金鑰 URI

Tink 需要統一資源識別碼 (URI) 才能使用 KMS 金鑰。

如要建構這個 URI,請使用 KMS 在建立金鑰時指派給金鑰的專屬 ID。新增適當的 KMS 專屬前置字串,並按照下表所述的支援金鑰 URI 格式操作:

KMS KMS 識別碼前置字串 金鑰 URI 格式
AWS KMS aws-kms:// aws-kms://arn:aws:kms:[region]:[account-id]:key/[key-id]
GCP KMS gcp-kms:// gcp-kms://projects/*/locations/*/keyRings/*/cryptoKeys/*
HashiCorp Vault hcvault:// hcvault://[key-id]

取得主要憑證

準備必要憑證,讓 Tink 向外部 KMS 進行驗證。

憑證的確切形式取決於 KMS:

如未提供憑證,Tink 會嘗試載入預設憑證。詳情請參閱 KMS 專屬說明文件:

步驟 3:建立及儲存加密金鑰集

使用 Tink 的 API (適用於 Google Cloud KMS、AWS KMS 或 HashiCorp Vault) 或 Tinkey 產生金鑰集,使用外部 KMS 加密,然後儲存在某處。

Tinkey

tinkey create-keyset --key-template AES128_GCM \
  --out-format json --out encrypted_aead_keyset.json \
  --master-key-uri gcp-kms://projects/tink-examples/locations/global/keyRings/foo/cryptoKeys/bar \
  --credential gcp_credentials.json

Java

本範例需要 Google Cloud KMS 擴充功能 tink-java-gcpkms

package encryptedkeyset;

import static java.nio.charset.StandardCharsets.UTF_8;

import com.google.crypto.tink.Aead;
import com.google.crypto.tink.KeysetHandle;
import com.google.crypto.tink.TinkJsonProtoKeysetFormat;
import com.google.crypto.tink.aead.AeadConfig;
import com.google.crypto.tink.aead.PredefinedAeadParameters;
import com.google.crypto.tink.integration.gcpkms.GcpKmsClient;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

/**
 * A command-line utility for working with encrypted keysets.
 *
 * <p>It requires the following arguments:
 *
 * <ul>
 *   <li>mode: Can be "generate", "encrypt" or "decrypt". If mode is "generate", it will generate a
 *       keyset, encrypt it and store it in the key-file argument. If mode is "encrypt" or
 *       "decrypt", it will read and decrypt an keyset from the key-file argument, and use it to
 *       encrypt or decrypt the input-file argument.
 *   <li>kek-uri: Use this Cloud KMS' key as the key-encrypting-key for envelope encryption.
 *   <li>gcp-credential-file: Use this JSON credential file to connect to Cloud KMS.
 *   <li>input-file: If mode is "encrypt" or "decrypt", read the input from this file.
 *   <li>output-file: If mode is "encrypt" or "decrypt", write the result to this file.
 */
public final class EncryptedKeysetExample {
  private static final String MODE_ENCRYPT = "encrypt";
  private static final String MODE_DECRYPT = "decrypt";
  private static final String MODE_GENERATE = "generate";
  private static final byte[] EMPTY_ASSOCIATED_DATA = new byte[0];

  public static void main(String[] args) throws Exception {
    if (args.length != 4 && args.length != 6) {
      System.err.printf("Expected 4 or 6 parameters, got %d\n", args.length);
      System.err.println(
          "Usage: java EncryptedKeysetExample generate/encrypt/decrypt key-file kek-uri"
              + " gcp-credential-file input-file output-file");
      System.exit(1);
    }
    String mode = args[0];
    if (!mode.equals(MODE_ENCRYPT) && !mode.equals(MODE_DECRYPT) && !mode.equals(MODE_GENERATE)) {
      System.err.print("The first argument should be either encrypt, decrypt or generate");
      System.exit(1);
    }
    Path keyFile = Paths.get(args[1]);
    String kekUri = args[2];
    String gcpCredentialFilename = args[3];

    // Initialise Tink: register all AEAD key types with the Tink runtime
    AeadConfig.register();

    // From the key-encryption key (KEK) URI, create a remote AEAD primitive for encrypting Tink
    // keysets.
    Aead kekAead = new GcpKmsClient().withCredentials(gcpCredentialFilename).getAead(kekUri);

    if (mode.equals(MODE_GENERATE)) {
      KeysetHandle handle = KeysetHandle.generateNew(PredefinedAeadParameters.AES128_GCM);

      String serializedEncryptedKeyset =
          TinkJsonProtoKeysetFormat.serializeEncryptedKeyset(
              handle, kekAead, EMPTY_ASSOCIATED_DATA);
      Files.write(keyFile, serializedEncryptedKeyset.getBytes(UTF_8));
      return;
    }

    // Use the primitive to encrypt/decrypt files

    // Read the encrypted keyset
    KeysetHandle handle =
        TinkJsonProtoKeysetFormat.parseEncryptedKeyset(
            new String(Files.readAllBytes(keyFile), UTF_8), kekAead, EMPTY_ASSOCIATED_DATA);

    // Get the primitive
    Aead aead = handle.getPrimitive(Aead.class);

    Path inputFile = Paths.get(args[4]);
    Path outputFile = Paths.get(args[5]);

    if (mode.equals(MODE_ENCRYPT)) {
      byte[] plaintext = Files.readAllBytes(inputFile);
      byte[] ciphertext = aead.encrypt(plaintext, EMPTY_ASSOCIATED_DATA);
      Files.write(outputFile, ciphertext);
    } else if (mode.equals(MODE_DECRYPT)) {
      byte[] ciphertext = Files.readAllBytes(inputFile);
      byte[] plaintext = aead.decrypt(ciphertext, EMPTY_ASSOCIATED_DATA);
      Files.write(outputFile, plaintext);
    }
  }

  private EncryptedKeysetExample() {}
}

Go

import (
	"bytes"
	"fmt"
	"log"

	"github.com/tink-crypto/tink-go/v2/aead"
	"github.com/tink-crypto/tink-go/v2/keyset"
	"github.com/tink-crypto/tink-go/v2/testing/fakekms"
)

// The fake KMS should only be used in tests. It is not secure.
const keyURI = "fake-kms://CM2b3_MDElQKSAowdHlwZS5nb29nbGVhcGlzLmNvbS9nb29nbGUuY3J5cHRvLnRpbmsuQWVzR2NtS2V5EhIaEIK75t5L-adlUwVhWvRuWUwYARABGM2b3_MDIAE"

func Example_encryptedKeyset() {
	// Get a KEK (key encryption key) AEAD. This is usually a remote AEAD to a KMS. In this example,
	// we use a fake KMS to avoid making RPCs.
	client, err := fakekms.NewClient(keyURI)
	if err != nil {
		log.Fatal(err)
	}
	kekAEAD, err := client.GetAEAD(keyURI)
	if err != nil {
		log.Fatal(err)
	}

	// Generate a new keyset handle for the primitive we want to use.
	newHandle, err := keyset.NewHandle(aead.AES256GCMKeyTemplate())
	if err != nil {
		log.Fatal(err)
	}

	// Choose some associated data. This is the context in which the keyset will be used.
	keysetAssociatedData := []byte("keyset encryption example")

	// Encrypt the keyset with the KEK AEAD and the associated data.
	buf := new(bytes.Buffer)
	writer := keyset.NewBinaryWriter(buf)
	err = newHandle.WriteWithAssociatedData(writer, kekAEAD, keysetAssociatedData)
	if err != nil {
		log.Fatal(err)
	}
	encryptedKeyset := buf.Bytes()

	// The encrypted keyset can now be stored.

	// To use the primitive, we first need to decrypt the keyset. We use the same
	// KEK AEAD and the same associated data that we used to encrypt it.
	reader := keyset.NewBinaryReader(bytes.NewReader(encryptedKeyset))
	handle, err := keyset.ReadWithAssociatedData(reader, kekAEAD, keysetAssociatedData)
	if err != nil {
		log.Fatal(err)
	}

	// Get the primitive.
	primitive, err := aead.New(handle)
	if err != nil {
		log.Fatal(err)
	}

	// Use the primitive.
	plaintext := []byte("message")
	associatedData := []byte("example encryption")
	ciphertext, err := primitive.Encrypt(plaintext, associatedData)
	if err != nil {
		log.Fatal(err)
	}
	decrypted, err := primitive.Decrypt(ciphertext, associatedData)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(string(decrypted))
	// Output: message
}

Python

"""A command-line utility for generating, encrypting and storing keysets."""

from absl import app
from absl import flags
from absl import logging

import tink
from tink import aead
from tink.integration import gcpkms


FLAGS = flags.FLAGS

flags.DEFINE_enum('mode', None, ['generate', 'encrypt', 'decrypt'],
                  'The operation to perform.')
flags.DEFINE_string('keyset_path', None,
                    'Path to the keyset used for encryption.')
flags.DEFINE_string('kek_uri', None,
                    'The Cloud KMS URI of the key encryption key.')
flags.DEFINE_string('gcp_credential_path', None,
                    'Path to the GCP credentials JSON file.')
flags.DEFINE_string('input_path', None, 'Path to the input file.')
flags.DEFINE_string('output_path', None, 'Path to the output file.')
flags.DEFINE_string('associated_data', None,
                    'Optional associated data to use with the '
                    'encryption operation.')


def main(argv):
  del argv  # Unused.

  associated_data = b'' if not FLAGS.associated_data else bytes(
      FLAGS.associated_data, 'utf-8')

  # Initialise Tink
  aead.register()

  try:
    # Read the GCP credentials and setup client
    client = gcpkms.GcpKmsClient(FLAGS.kek_uri, FLAGS.gcp_credential_path)
  except tink.TinkError as e:
    logging.exception('Error creating GCP KMS client: %s', e)
    return 1

  # Create envelope AEAD primitive using AES128 GCM for encrypting the data
  try:
    remote_aead = client.get_aead(FLAGS.kek_uri)
  except tink.TinkError as e:
    logging.exception('Error creating primitive: %s', e)
    return 1

  if FLAGS.mode == 'generate':
    # Generate a new keyset
    try:
      key_template = aead.aead_key_templates.AES128_GCM
      keyset_handle = tink.new_keyset_handle(key_template)
    except tink.TinkError as e:
      logging.exception('Error creating primitive: %s', e)
      return 1

    # Encrypt the keyset_handle with the remote key-encryption key (KEK)
    with open(FLAGS.keyset_path, 'wt') as keyset_file:
      try:
        keyset_encryption_associated_data = 'encrypted keyset example'
        serialized_encrypted_keyset = (
            tink.json_proto_keyset_format.serialize_encrypted(
                keyset_handle, remote_aead, keyset_encryption_associated_data
            )
        )
        keyset_file.write(serialized_encrypted_keyset)
      except tink.TinkError as e:
        logging.exception('Error writing key: %s', e)
        return 1
    return 0

  # Use the keyset to encrypt/decrypt data

  # Read the encrypted keyset into a keyset_handle
  with open(FLAGS.keyset_path, 'rt') as keyset_file:
    try:
      serialized_encrypted_keyset = keyset_file.read()
      keyset_encryption_associated_data = 'encrypted keyset example'
      keyset_handle = tink.json_proto_keyset_format.parse_encrypted(
          serialized_encrypted_keyset,
          remote_aead,
          keyset_encryption_associated_data,
      )
    except tink.TinkError as e:
      logging.exception('Error reading key: %s', e)
      return 1

  # Get the primitive
  try:
    cipher = keyset_handle.primitive(aead.Aead)
  except tink.TinkError as e:
    logging.exception('Error creating primitive: %s', e)
    return 1

  with open(FLAGS.input_path, 'rb') as input_file:
    input_data = input_file.read()
    if FLAGS.mode == 'decrypt':
      output_data = cipher.decrypt(input_data, associated_data)
    elif FLAGS.mode == 'encrypt':
      output_data = cipher.encrypt(input_data, associated_data)
    else:
      logging.error(
          'Unsupported mode %s. Please choose "encrypt" or "decrypt".',
          FLAGS.mode,
      )
      return 1

    with open(FLAGS.output_path, 'wb') as output_file:
      output_file.write(output_data)


if __name__ == '__main__':
  flags.mark_flags_as_required([
      'mode', 'keyset_path', 'kek_uri', 'gcp_credential_path'])
  app.run(main)

步驟 4:輪替金鑰

為確保系統安全,您必須輪替金鑰。

  1. 在 KMS 中啟用自動金鑰輪替。
  2. 決定適合的金鑰輪替頻率。這取決於資料的機密程度、需要加密的郵件數量,以及是否需要與外部合作夥伴協調輪替作業。

    • 如果是對稱式加密,請使用 30 到 90 天的金鑰。
    • 如果是非對稱式加密,輪替頻率可以較低,但前提是您能安全地撤銷金鑰。

如要進一步瞭解如何輪替金鑰,請參閱 KMS 專屬說明文件: