Manage Keys

Tink offers solutions to avoid improper key management, which is a major source of risk.


After selecting a primitive and key type for your use case (in the preceding I want to... section), manage your keys with the external Key Management System (KMS) you chose:

  1. Create a key encryption key (KEK) in your KMS to protect your keys.

  2. Retrieve a key URI and key credentials from your KMS to pass to Tink.

  3. Use Tink's APIs or Tinkey to generate an encrypted keyset. After your keys are encrypted, you can store them wherever you want.

  4. Rotate your keys to avoid extensively reusing your keys and to recover from key compromise.

Step 1: Create a KEK in the external KMS

Create a key encryption key (KEK) in your external KMS. The KEK protects your keys by encrypting them, adding an extra layer of security.

Refer to KMS-specific documentation to create a KEK:

Step 2: Get a key URI and credentials

You can retrieve both a key URI and key credentials from your KMS.

Get the key URI

Tink requires a Uniform Resource Identifier (URI) to work with KMS keys.

To construct this URI, use the unique identifier the KMS assigns to the key when it is created. Add the appropriate KMS-specific prefix and follow the format of supported key URIs as described in this table:

KMS KMS identifier prefix Key URI format
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]

Get the key credentials

Prepare the necessary credentials so that Tink can authenticate to the external KMS.

The exact form of the credential is KMS-specific:

If you don't supply credentials, Tink attempts to load default credentials. For more information, refer to KMS-specific documentation:

Step 3: Create and store an encrypted keyset

Use Tink's APIs (for Google Cloud KMS, AWS KMS, or HashiCorp Vault) or Tinkey to generate a keyset, encrypt it using the external KMS, and store it somewhere.


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


For this example you need the Google Cloud KMS extension tink-java-gcpkms.

package encryptedkeyset;

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

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);
          "Usage: java EncryptedKeysetExample generate/encrypt/decrypt key-file kek-uri"
              + " gcp-credential-file input-file output-file");
    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");
    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

    // 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 =
              handle, kekAead, EMPTY_ASSOCIATED_DATA);
      Files.write(keyFile, serializedEncryptedKeyset.getBytes(UTF_8));

    // Use the primitive to encrypt/decrypt files

    // Read the encrypted keyset
    KeysetHandle handle =
            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() {}


import (


// 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 {
	kekAEAD, err := client.GetAEAD(keyURI)
	if err != nil {

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

	// 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 {
	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 {

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

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


"""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.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

    # 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 AES256 GCM for encrypting the data
    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
      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:
        keyset_encryption_associated_data = 'encrypted keyset example'
        serialized_encrypted_keyset = (
                keyset_handle, remote_aead, keyset_encryption_associated_data
      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:
      serialized_encrypted_keyset =
      keyset_encryption_associated_data = 'encrypted keyset example'
      keyset_handle = tink.json_proto_keyset_format.parse_encrypted(
    except tink.TinkError as e:
      logging.exception('Error reading key: %s', e)
      return 1

  # Get the primitive
    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 =
    if FLAGS.mode == 'decrypt':
      output_data = cipher.decrypt(input_data, associated_data)
    elif FLAGS.mode == 'encrypt':
      output_data = cipher.encrypt(input_data, associated_data)
          'Unsupported mode %s. Please choose "encrypt" or "decrypt".',
      return 1

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

if __name__ == '__main__':
      'mode', 'keyset_path', 'kek_uri', 'gcp_credential_path'])

Step 4: Rotate keys

To ensure the security of your system, you must rotate keys.

  1. Enable automatic key rotation in your KMS.
  2. Determine a suitable frequency for rotating keys. This depends on how sensitive your data is, how many messages you need to encrypt, and whether you have to coordinate the rotation with external partners.

    • For symmetric encryption, use 30- to 90-day keys.
    • For asymmetric encryption, the rotation frequency can be lower, but only if you can securely revoke keys.

Learn more about key rotation in KMS-specific documentation: