I want to encrypt data deterministically

We recommend using the Deterministic AEAD primitive with the AES256_SIV key type.

Deterministic Authenticated Encryption with Associated Data (Deterministic AEAD) produces stable ciphertexts: encrypting a given plaintext always returns the same ciphertext. It is symmetric, which means it uses a single key for both encryption and decryption.

Caution: Because of the deterministic property, Deterministic AEAD can lead to loss of secrecy. Imagine a system with two possible messages, "yes" and "no." An attacker only has to find out which ciphertext corresponds to each message to read them.

Examples

The following examples get you started using the Deterministic AEAD primitive:

Warning: These examples use cleartext keysets; cleartext keysets allow anyone with access to the source code to extract cryptographic keys. In practice you should protect your keys with proper key management.

C++

// A command-line utility for testing Tink Deterministic AEAD.
#include <iostream>
#include <memory>
#include <ostream>
#include <string>

#include "absl/flags/flag.h"
#include "absl/flags/parse.h"
#include "absl/log/check.h"
#include "absl/strings/string_view.h"
#include "tink/config/global_registry.h"
#include "tink/daead/deterministic_aead_config.h"
#include "tink/deterministic_aead.h"
#include "util/util.h"
#include "tink/keyset_handle.h"
#include "tink/util/status.h"

ABSL_FLAG(std::string, keyset_filename, "", "Keyset file in JSON format");
ABSL_FLAG(std::string, mode, "", "Mode of operation {encrypt|decrypt}");
ABSL_FLAG(std::string, input_filename, "", "Filename to operate on");
ABSL_FLAG(std::string, output_filename, "", "Output file name");
ABSL_FLAG(std::string, associated_data, "",
          "Associated data for Deterministic AEAD (default: empty");

namespace {

using ::crypto::tink::DeterministicAead;
using ::crypto::tink::DeterministicAeadConfig;
using ::crypto::tink::KeysetHandle;
using ::crypto::tink::util::Status;
using ::crypto::tink::util::StatusOr;

constexpr absl::string_view kEncrypt = "encrypt";
constexpr absl::string_view kDecrypt = "decrypt";

void ValidateParams() {
  // ...
}

}  // namespace

namespace tink_cc_examples {

// Deterministic AEAD example CLI implementation.
Status DeterministicAeadCli(absl::string_view mode,
                            const std::string& keyset_filename,
                            const std::string& input_filename,
                            const std::string& output_filename,
                            absl::string_view associated_data) {
  Status result = DeterministicAeadConfig::Register();
  if (!result.ok()) return result;

  // Read keyset from file.
  StatusOr<std::unique_ptr<KeysetHandle>> keyset_handle =
      ReadJsonCleartextKeyset(keyset_filename);
  if (!keyset_handle.ok()) return keyset_handle.status();

  // Get the primitive.
  StatusOr<std::unique_ptr<DeterministicAead>> daead =
      (*keyset_handle)
          ->GetPrimitive<crypto::tink::DeterministicAead>(
              crypto::tink::ConfigGlobalRegistry());
  if (!daead.ok()) return daead.status();

  // Read the input.
  StatusOr<std::string> input_file_content = ReadFile(input_filename);
  if (!input_file_content.ok()) return input_file_content.status();

  // Compute the output.
  std::string output;
  if (mode == kEncrypt) {
    StatusOr<std::string> result = (*daead)->EncryptDeterministically(
        *input_file_content, associated_data);
    if (!result.ok()) return result.status();
    output = *result;
  } else if (mode == kDecrypt) {
    StatusOr<std::string> result = (*daead)->DecryptDeterministically(
        *input_file_content, associated_data);
    if (!result.ok()) return result.status();
    output = *result;
  }

  // Write output to file.
  return WriteToFile(output, output_filename);
}

}  // namespace tink_cc_examples

int main(int argc, char** argv) {
  absl::ParseCommandLine(argc, argv);

  ValidateParams();

  std::string mode = absl::GetFlag(FLAGS_mode);
  std::string keyset_filename = absl::GetFlag(FLAGS_keyset_filename);
  std::string input_filename = absl::GetFlag(FLAGS_input_filename);
  std::string output_filename = absl::GetFlag(FLAGS_output_filename);
  std::string associated_data = absl::GetFlag(FLAGS_associated_data);

  std::clog << "Using keyset from file " << keyset_filename
            << " to Deterministic AEAD-" << mode << " file " << input_filename
            << " with associated data '" << associated_data << "'."
            << std::endl;
  std::clog << "The resulting output will be written to " << output_filename
            << "." << std::endl;

  CHECK_OK(tink_cc_examples::DeterministicAeadCli(
      mode, keyset_filename, input_filename, output_filename, associated_data));
  return 0;
}
deterministic_aead_cli.cc

Go

import (
	"bytes"
	"fmt"
	"log"

	"github.com/tink-crypto/tink-go/v2/daead"
	"github.com/tink-crypto/tink-go/v2/insecurecleartextkeyset"
	"github.com/tink-crypto/tink-go/v2/keyset"
)

func Example() {
	// A keyset created with "tinkey create-keyset --key-template=AES256_SIV". Note
	// that this keyset has the secret key information in cleartext.
	jsonKeyset := `{
			"key": [{
				"keyData": {
						"keyMaterialType":
								"SYMMETRIC",
						"typeUrl":
								"type.googleapis.com/google.crypto.tink.AesSivKey",
						"value":
								"EkAl9HCMmKTN1p3V186uhZpJQ+tivyc4IKyE+opg6SsEbWQ/WesWHzwCRrlgRuxdaggvgMzwWhjPnkk9gptBnGLK"
				},
				"keyId": 1919301694,
				"outputPrefixType": "TINK",
				"status": "ENABLED"
		}],
		"primaryKeyId": 1919301694
	}`

	// Create a keyset handle from the cleartext keyset in the previous
	// step. The keyset handle provides abstract access to the underlying keyset to
	// limit the exposure of accessing the raw key material. WARNING: In practice,
	// it is unlikely you will want to use a insecurecleartextkeyset, as it implies
	// that your key material is passed in cleartext, which is a security risk.
	// Consider encrypting it with a remote key in Cloud KMS, AWS KMS or HashiCorp Vault.
	// See https://github.com/google/tink/blob/master/docs/GOLANG-HOWTO.md#storing-and-loading-existing-keysets.
	keysetHandle, err := insecurecleartextkeyset.Read(
		keyset.NewJSONReader(bytes.NewBufferString(jsonKeyset)))
	if err != nil {
		log.Fatal(err)
	}

	// Retrieve the DAEAD primitive we want to use from the keyset handle.
	primitive, err := daead.New(keysetHandle)
	if err != nil {
		log.Fatal(err)
	}

	// Use the primitive to encrypt a message. In this case the primary key of the
	// keyset will be used (which is also the only key in this example).
	plaintext := []byte("message")
	associatedData := []byte("associated data")
	ciphertext, err := primitive.EncryptDeterministically(plaintext, associatedData)
	if err != nil {
		log.Fatal(err)
	}

	// Use the primitive to decrypt the message. Decrypt finds the correct key in
	// the keyset and decrypts the ciphertext. If no key is found or decryption
	// fails, it returns an error.
	decrypted, err := primitive.DecryptDeterministically(ciphertext, associatedData)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Println(ciphertext)
	fmt.Println(string(decrypted))
	// Output:
	// [1 114 102 56 62 150 98 146 84 99 211 36 127 214 229 231 157 56 143 192 250 132 32 153 124 244 238 112]
	// message
}
daead_test.go

Java

package deterministicaead;

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

import com.google.crypto.tink.DeterministicAead;
import com.google.crypto.tink.InsecureSecretKeyAccess;
import com.google.crypto.tink.KeysetHandle;
import com.google.crypto.tink.TinkJsonProtoKeysetFormat;
import com.google.crypto.tink.daead.DeterministicAeadConfig;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

/**
 * A command-line utility for encrypting small files with Deterministic AEAD.
 *
 * <p>It loads cleartext keys from disk - this is not recommended!
 *
 * <p>It requires the following arguments:
 *
 * <ul>
 *   <li>mode: Can be "encrypt" or "decrypt" to encrypt/decrypt the input to the output.
 *   <li>key-file: Read the key material from this file.
 *   <li>input-file: Read the input from this file.
 *   <li>output-file: Write the result to this file.
 *   <li>[optional] associated-data: Associated data used for the encryption or decryption.
 */
public final class DeterministicAeadExample {
  private static final String MODE_ENCRYPT = "encrypt";
  private static final String MODE_DECRYPT = "decrypt";

  public static void main(String[] args) throws Exception {
    if (args.length != 4 && args.length != 5) {
      System.err.printf("Expected 4 or 5 parameters, got %d\n", args.length);
      System.err.println(
          "Usage: java DeterministicAeadExample encrypt/decrypt key-file input-file output-file"
              + " [associated-data]");
      System.exit(1);
    }
    String mode = args[0];
    Path keyFile = Paths.get(args[1]);
    Path inputFile = Paths.get(args[2]);
    Path outputFile = Paths.get(args[3]);
    byte[] associatedData = new byte[0];
    if (args.length == 5) {
      associatedData = args[4].getBytes(UTF_8);
    }

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

    // Read the keyset into a KeysetHandle
    KeysetHandle handle =
        TinkJsonProtoKeysetFormat.parseKeyset(
            new String(Files.readAllBytes(keyFile), UTF_8), InsecureSecretKeyAccess.get());

    // Get the primitive
    DeterministicAead daead = handle.getPrimitive(DeterministicAead.class);

    // Use the primitive to encrypt/decrypt files.
    if (MODE_ENCRYPT.equals(mode)) {
      byte[] plaintext = Files.readAllBytes(inputFile);
      byte[] ciphertext = daead.encryptDeterministically(plaintext, associatedData);
      Files.write(outputFile, ciphertext);
    } else if (MODE_DECRYPT.equals(mode)) {
      byte[] ciphertext = Files.readAllBytes(inputFile);
      byte[] plaintext = daead.decryptDeterministically(ciphertext, associatedData);
      Files.write(outputFile, plaintext);
    } else {
      System.err.println("The first argument must be either encrypt or decrypt, got: " + mode);
      System.exit(1);
    }

    System.exit(0);
  }

  private DeterministicAeadExample() {}
}
DeterministicAeadExample.java

Python

import tink
from tink import daead
from tink import secret_key_access


def example():
  """Encrypt and decrypt using deterministic AEAD."""
  # Register the deterministic AEAD key manager. This is needed to create a
  # DeterministicAead primitive later.
  daead.register()

  # A keyset created with "tinkey create-keyset --key-template=AES256_SIV". Note
  # that this keyset has the secret key information in cleartext.
  keyset = r"""{
      "key": [{
          "keyData": {
              "keyMaterialType":
                  "SYMMETRIC",
              "typeUrl":
                  "type.googleapis.com/google.crypto.tink.AesSivKey",
              "value":
                  "EkAl9HCMmKTN1p3V186uhZpJQ+tivyc4IKyE+opg6SsEbWQ/WesWHzwCRrlgRuxdaggvgMzwWhjPnkk9gptBnGLK"
          },
          "keyId": 1919301694,
          "outputPrefixType": "TINK",
          "status": "ENABLED"
      }],
      "primaryKeyId": 1919301694
  }"""

  # Create a keyset handle from the cleartext keyset in the previous
  # step. The keyset handle provides abstract access to the underlying keyset to
  # limit the exposure of accessing the raw key material. WARNING: In practice,
  # it is unlikely you will want to use a cleartext_keyset_handle, as it implies
  # that your key material is passed in cleartext which is a security risk.
  keyset_handle = tink.json_proto_keyset_format.parse(
      keyset, secret_key_access.TOKEN
  )

  # Retrieve the DeterministicAead primitive we want to use from the keyset
  # handle.
  primitive = keyset_handle.primitive(daead.DeterministicAead)

  # Use the primitive to encrypt a message. In this case the primary key of the
  # keyset will be used (which is also the only key in this example).
  ciphertext = primitive.encrypt_deterministically(b'msg', b'associated_data')

  # Use the primitive to decrypt the message. Decrypt finds the correct key in
  # the keyset and decrypts the ciphertext. If no key is found or decryption
  # fails, it raises an error.
  output = primitive.decrypt_deterministically(ciphertext, b'associated_data')
deterministic_aead_basic.py