We recommend the Streaming AEAD primitive with AES128_GCM_HKDF_1MB key type for most file encryption use cases.
Streaming Authenticated Encryption with Associated Data (Streaming AEAD) is useful for encrypting live data streams or large files that don't fit in memory. Similar to AEAD, it is symmetric, using a single key for both encryption and decryption.
The following examples get you started using the Streaming AEAD primitive:
Go
import (
"bytes"
"fmt"
"io"
"log"
"os"
"path/filepath"
"github.com/tink-crypto/tink-go/v2/insecurecleartextkeyset"
"github.com/tink-crypto/tink-go/v2/keyset"
"github.com/tink-crypto/tink-go/v2/streamingaead"
)
func Example() {
// A keyset created with "tinkey create-keyset --key-template=AES256_CTR_HMAC_SHA256_1MB". Note
// that this keyset has the secret key information in cleartext.
jsonKeyset := `{
"primaryKeyId": 1720777699,
"key": [{
"keyData": {
"typeUrl": "type.googleapis.com/google.crypto.tink.AesCtrHmacStreamingKey",
"keyMaterialType": "SYMMETRIC",
"value": "Eg0IgCAQIBgDIgQIAxAgGiDtesd/4gCnQdTrh+AXodwpm2b6BFJkp043n+8mqx0YGw=="
},
"outputPrefixType": "RAW",
"keyId": 1720777699,
"status": "ENABLED"
}]
}`
// 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 an 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 StreamingAEAD primitive we want to use from the keyset handle.
primitive, err := streamingaead.New(keysetHandle)
if err != nil {
log.Fatal(err)
}
// Create a file with the plaintext.
dir, err := os.MkdirTemp("", "streamingaead")
if err != nil {
log.Fatal(err)
}
defer os.RemoveAll(dir)
plaintextPath := filepath.Join(dir, "plaintext")
if err := os.WriteFile(plaintextPath, []byte("this data needs to be encrypted"), 0666); err != nil {
log.Fatal(err)
}
plaintextFile, err := os.Open(plaintextPath)
if err != nil {
log.Fatal(err)
}
// associatedData defines the context of the encryption. Here, we include the path of the
// plaintext file.
associatedData := []byte("associatedData for " + plaintextPath)
// Encrypt the plaintext file and write the output to the ciphertext file. In this case the
// primary key of the keyset will be used (which is also the only key in this example).
ciphertextPath := filepath.Join(dir, "ciphertext")
ciphertextFile, err := os.Create(ciphertextPath)
if err != nil {
log.Fatal(err)
}
w, err := primitive.NewEncryptingWriter(ciphertextFile, associatedData)
if err != nil {
log.Fatal(err)
}
if _, err := io.Copy(w, plaintextFile); err != nil {
log.Fatal(err)
}
if err := w.Close(); err != nil {
log.Fatal(err)
}
if err := ciphertextFile.Close(); err != nil {
log.Fatal(err)
}
if err := plaintextFile.Close(); err != nil {
log.Fatal(err)
}
// Decrypt the ciphertext file and write the output to the decrypted file. The
// decryption finds the correct key in the keyset and decrypts the ciphertext.
// If no key is found or decryption fails, it returns an error.
ciphertextFile, err = os.Open(ciphertextPath)
if err != nil {
log.Fatal(err)
}
decryptedPath := filepath.Join(dir, "decrypted")
decryptedFile, err := os.Create(decryptedPath)
if err != nil {
log.Fatal(err)
}
r, err := primitive.NewDecryptingReader(ciphertextFile, associatedData)
if err != nil {
log.Fatal(err)
}
if _, err := io.Copy(decryptedFile, r); err != nil {
log.Fatal(err)
}
if err := decryptedFile.Close(); err != nil {
log.Fatal(err)
}
if err := ciphertextFile.Close(); err != nil {
log.Fatal(err)
}
// Print the content of the decrypted file.
b, err := os.ReadFile(decryptedPath)
if err != nil {
log.Fatal(err)
}
fmt.Println(string(b))
// Output: this data needs to be encrypted
}
Java
package streamingaead;
import static java.nio.charset.StandardCharsets.UTF_8;
import com.google.crypto.tink.InsecureSecretKeyAccess;
import com.google.crypto.tink.KeysetHandle;
import com.google.crypto.tink.StreamingAead;
import com.google.crypto.tink.TinkJsonProtoKeysetFormat;
import com.google.crypto.tink.streamingaead.StreamingAeadConfig;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.security.GeneralSecurityException;
/**
* A command-line utility for encrypting files with Streaming 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 StreamingAeadExample {
private static final String MODE_ENCRYPT = "encrypt";
private static final String MODE_DECRYPT = "decrypt";
private static final int BLOCK_SIZE_IN_BYTES = 8 * 1024;
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 StreamingAeadExample 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);
}
// Initalise Tink: register all Streaming AEAD key types with the Tink runtime
StreamingAeadConfig.register();
// Read the keyset into a KeysetHandle
KeysetHandle handle =
TinkJsonProtoKeysetFormat.parseKeyset(
new String(Files.readAllBytes(keyFile), UTF_8), InsecureSecretKeyAccess.get());
// Get the primitive
StreamingAead streamingAead = handle.getPrimitive(StreamingAead.class);
// Use the primitive to encrypt/decrypt files
if (MODE_ENCRYPT.equals(mode)) {
encryptFile(streamingAead, inputFile, outputFile, associatedData);
} else if (MODE_DECRYPT.equals(mode)) {
decryptFile(streamingAead, inputFile, outputFile, associatedData);
} else {
System.err.println("The first argument must be either encrypt or decrypt, got: " + mode);
System.exit(1);
}
}
private static void encryptFile(
StreamingAead streamingAead, Path inputFile, Path outputFile, byte[] associatedData)
throws GeneralSecurityException, IOException {
try (WritableByteChannel plaintextChannel =
streamingAead.newEncryptingChannel(
FileChannel.open(outputFile, StandardOpenOption.WRITE, StandardOpenOption.CREATE),
associatedData);
FileChannel inputChannel = FileChannel.open(inputFile, StandardOpenOption.READ)) {
ByteBuffer byteBuffer = ByteBuffer.allocate(BLOCK_SIZE_IN_BYTES);
while (true) {
int read = inputChannel.read(byteBuffer);
if (read <= 0) {
return;
}
byteBuffer.flip();
while (byteBuffer.hasRemaining()) {
plaintextChannel.write(byteBuffer);
}
byteBuffer.clear();
}
}
}
private static void decryptFile(
StreamingAead streamingAead, Path inputFile, Path outputFile, byte[] associatedData)
throws GeneralSecurityException, IOException {
try (ReadableByteChannel plaintextChannel =
streamingAead.newDecryptingChannel(
FileChannel.open(inputFile, StandardOpenOption.READ), associatedData);
FileChannel outputChannel =
FileChannel.open(outputFile, StandardOpenOption.WRITE, StandardOpenOption.CREATE)) {
ByteBuffer byteBuffer = ByteBuffer.allocate(BLOCK_SIZE_IN_BYTES);
while (true) {
int read = plaintextChannel.read(byteBuffer);
if (read <= 0) {
return;
}
byteBuffer.flip();
while (byteBuffer.hasRemaining()) {
outputChannel.write(byteBuffer);
}
byteBuffer.clear();
}
}
}
private StreamingAeadExample() {}
}
Python
"""A command-line utility for using streaming AEAD for a file.
It loads cleartext keys from disk - this is not recommended!
It requires 4 arguments (and one optional one):
mode: either 'encrypt' or 'decrypt'
keyset_path: name of the file with the keyset to be used for encryption or
decryption
input_path: name of the file with the input data to be encrypted or decrypted
output_path: name of the file to write the ciphertext respectively plaintext
to
[optional] associated_data: the associated data used for encryption/decryption
provided as a string.
"""
from typing import BinaryIO
from absl import app
from absl import flags
from absl import logging
import tink
from tink import secret_key_access
from tink import streaming_aead
FLAGS = flags.FLAGS
BLOCK_SIZE = 1024 * 1024 # The CLI tool will read/write at most 1 MB at once.
flags.DEFINE_enum('mode', None, ['encrypt', 'decrypt'],
'Selects if the file should be encrypted or decrypted.')
flags.DEFINE_string('keyset_path', None,
'Path to the keyset used for encryption or decryption.')
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,
'Associated data used for the encryption or decryption.')
def read_as_blocks(file: BinaryIO):
"""Generator function to read from a file BLOCK_SIZE bytes.
Args:
file: The file object to read from.
Yields:
Returns up to BLOCK_SIZE bytes from the file.
"""
while True:
data = file.read(BLOCK_SIZE)
# If file was opened in rawIO, EOF is only reached when b'' is returned.
# pylint: disable=g-explicit-bool-comparison
if data == b'':
break
# pylint: enable=g-explicit-bool-comparison
yield data
def encrypt_file(input_file: BinaryIO, output_file: BinaryIO,
associated_data: bytes,
primitive: streaming_aead.StreamingAead):
"""Encrypts a file with the given streaming AEAD primitive.
Args:
input_file: File to read from.
output_file: File to write to.
associated_data: Associated data provided for the AEAD.
primitive: The streaming AEAD primitive used for encryption.
"""
with primitive.new_encrypting_stream(output_file,
associated_data) as enc_stream:
for data_block in read_as_blocks(input_file):
enc_stream.write(data_block)
def decrypt_file(input_file: BinaryIO, output_file: BinaryIO,
associated_data: bytes,
primitive: streaming_aead.StreamingAead):
"""Decrypts a file with the given streaming AEAD primitive.
This function will cause the program to exit with 1 if the decryption fails.
Args:
input_file: File to read from.
output_file: File to write to.
associated_data: Associated data provided for the AEAD.
primitive: The streaming AEAD primitive used for decryption.
"""
try:
with primitive.new_decrypting_stream(input_file,
associated_data) as dec_stream:
for data_block in read_as_blocks(dec_stream):
output_file.write(data_block)
except tink.TinkError as e:
logging.exception('Error decrypting ciphertext: %s', e)
exit(1)
def main(argv):
del argv
associated_data = b'' if not FLAGS.associated_data else bytes(
FLAGS.associated_data, 'utf-8')
# Initialise Tink.
try:
streaming_aead.register()
except tink.TinkError as e:
logging.exception('Error initialising Tink: %s', e)
return 1
# Read the keyset into a keyset_handle.
with open(FLAGS.keyset_path, 'rt') as keyset_file:
try:
text = keyset_file.read()
keyset_handle = tink.json_proto_keyset_format.parse(
text, secret_key_access.TOKEN
)
except tink.TinkError as e:
logging.exception('Error reading key: %s', e)
return 1
# Get the primitive.
try:
streaming_aead_primitive = keyset_handle.primitive(
streaming_aead.StreamingAead)
except tink.TinkError as e:
logging.exception('Error creating streaming AEAD primitive from keyset: %s',
e)
return 1
# Encrypt or decrypt the file.
with open(FLAGS.input_path, 'rb') as input_file:
with open(FLAGS.output_path, 'wb') as output_file:
if FLAGS.mode == 'encrypt':
encrypt_file(input_file, output_file, associated_data,
streaming_aead_primitive)
elif FLAGS.mode == 'decrypt':
decrypt_file(input_file, output_file, associated_data,
streaming_aead_primitive)
if __name__ == '__main__':
flags.mark_flag_as_required('mode')
flags.mark_flag_as_required('keyset_path')
flags.mark_flag_as_required('input_path')
flags.mark_flag_as_required('output_path')
app.run(main)