Saya ingin menandatangani data secara digital

Sebaiknya gunakan primitif Tanda Tangan Digital dengan jenis kunci ECDSA_P256 untuk sebagian besar kasus penggunaan.

Primitive Tanda Tangan Digital memastikan bahwa tidak ada yang telah memodifikasi data Anda dan membuktikan bahwa data berasal dari Anda. Enkripsi ini bersifat asimetris, menggunakan kunci pribadi untuk menandatangani data dan kunci publik memverifikasinya.

Contoh berikut membantu Anda mulai menggunakan primitif Tanda Tangan Digital:

C++GoJavaObj-CPython

// A utility for signing and verifying files using digital signatures.
#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 "util/util.h"
#include "tink/keyset_handle.h"
#include "tink/public_key_sign.h"
#include "tink/public_key_verify.h"
#include "tink/signature/signature_config.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 (sign|verify)");
ABSL_FLAG(std::string, input_filename, "", "Filename to operate on");
ABSL_FLAG(std::string, signature_filename, "", "Path to the signature file");

namespace {

using ::crypto::tink::KeysetHandle;
using ::crypto::tink::PublicKeySign;
using ::crypto::tink::PublicKeyVerify;
using ::crypto::tink::util::Status;
using ::crypto::tink::util::StatusOr;

constexpr absl::string_view kSign = "sign";
constexpr absl::string_view kVerify = "verify";

void ValidateParams() {
  // ...
}

}  // namespace

namespace tink_cc_examples {

// Digital signature example CLI implementation.
Status DigitalSignatureCli(absl::string_view mode,
                           const std::string& keyset_filename,
                           const std::string& input_filename,
                           const std::string& signature_filename) {
  Status result = crypto::tink::SignatureConfig::Register();
  if (!result.ok()) return result;

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

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

  if (mode == kSign) {
    StatusOr<std::unique_ptr<PublicKeySign>> public_key_sign =
        (*keyset_handle)
            ->GetPrimitive<crypto::tink::PublicKeySign>(
                crypto::tink::ConfigGlobalRegistry());
    if (!public_key_sign.ok()) return public_key_sign.status();

    StatusOr<std::string> signature =
        (*public_key_sign)->Sign(*input_file_content);
    if (!signature.ok()) return signature.status();

    return WriteToFile(*signature, signature_filename);
  } else {  // mode == kVerify
    StatusOr<std::unique_ptr<PublicKeyVerify>> public_key_verify =
        (*keyset_handle)
            ->GetPrimitive<crypto::tink::PublicKeyVerify>(
                crypto::tink::ConfigGlobalRegistry());
    if (!public_key_verify.ok()) return public_key_verify.status();

    // Read the signature.
    StatusOr<std::string> signature_file_content = ReadFile(signature_filename);
    if (!signature_file_content.ok()) return signature_file_content.status();

    return (*public_key_verify)
        ->Verify(*signature_file_content, *input_file_content);
  }
}

}  // 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 signature_filename = absl::GetFlag(FLAGS_signature_filename);

  std::clog << "Using keyset in " << keyset_filename << " to " << mode;
  if (mode == kSign) {
    std::clog << " file " << input_filename
              << "; the resulting signature is written to "
              << signature_filename << '\n';
  } else {  // mode == kVerify
    std::clog << " the signature in " << signature_filename
              << " over the content of " << input_filename << '\n';
  }

  CHECK_OK(tink_cc_examples::DigitalSignatureCli(
      mode, keyset_filename, input_filename, signature_filename));
  return 0;
}
digital_signatures_cli.cc

import (
	"bytes"
	"fmt"
	"log"

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

func Example() {
	// A private keyset created with
	// "tinkey create-keyset --key-template=ECDSA_P256 --out private_keyset.cfg".
	// Note that this keyset has the secret key information in cleartext.
	privateJSONKeyset := `{
		"key": [{
			"keyData": {
					"keyMaterialType":
							"ASYMMETRIC_PRIVATE",
					"typeUrl":
							"type.googleapis.com/google.crypto.tink.EcdsaPrivateKey",
					"value":
							"EkwSBggDEAIYAhogEiSZ9u2nDtvZuDgWgGsVTIZ5/V08N4ycUspTX0RYRrkiIHpEwHxQd1bImkyMvV2bqtUbgMh5uPSTdnUEGrPXdt56GiEA3iUi+CRN71qy0fOCK66xAW/IvFyjOGtxjppRhSFUneo="
			},
			"keyId": 611814836,
			"outputPrefixType": "TINK",
			"status": "ENABLED"
		}],
		"primaryKeyId": 611814836
	}`

	// The corresponding public keyset created with
	// "tinkey create-public-keyset --in private_keyset.cfg"
	publicJSONKeyset := `{
      "key": [{
          "keyData": {
              "keyMaterialType":
                  "ASYMMETRIC_PUBLIC",
              "typeUrl":
                  "type.googleapis.com/google.crypto.tink.EcdsaPublicKey",
              "value":
                  "EgYIAxACGAIaIBIkmfbtpw7b2bg4FoBrFUyGef1dPDeMnFLKU19EWEa5IiB6RMB8UHdWyJpMjL1dm6rVG4DIebj0k3Z1BBqz13beeg=="
          },
          "keyId": 611814836,
          "outputPrefixType": "TINK",
          "status": "ENABLED"
      }],
      "primaryKeyId": 611814836
  }`

	// Create a keyset handle from the cleartext private keyset in the previous
	// step. The keyset handle provides abstract access to the underlying keyset to
	// limit the access of 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.
	privateKeysetHandle, err := insecurecleartextkeyset.Read(
		keyset.NewJSONReader(bytes.NewBufferString(privateJSONKeyset)))
	if err != nil {
		log.Fatal(err)
	}

	// Retrieve the Signer primitive from privateKeysetHandle.
	signer, err := signature.NewSigner(privateKeysetHandle)
	if err != nil {
		log.Fatal(err)
	}

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

	// Create a keyset handle from the keyset containing the public key. Because the
	// public keyset does not contain any secrets, we can use [keyset.ReadWithNoSecrets].
	publicKeysetHandle, err := keyset.ReadWithNoSecrets(
		keyset.NewJSONReader(bytes.NewBufferString(publicJSONKeyset)))
	if err != nil {
		log.Fatal(err)
	}

	// Retrieve the Verifier primitive from publicKeysetHandle.
	verifier, err := signature.NewVerifier(publicKeysetHandle)
	if err != nil {
		log.Fatal(err)
	}

	if err = verifier.Verify(sig, data); err != nil {
		log.Fatal(err)
	}
	fmt.Printf("sig is valid")
	// Output: sig is valid
}
signature_test.go

package signature;

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.PublicKeySign;
import com.google.crypto.tink.PublicKeyVerify;
import com.google.crypto.tink.RegistryConfiguration;
import com.google.crypto.tink.TinkJsonProtoKeysetFormat;
import com.google.crypto.tink.signature.SignatureConfig;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

/**
 * A command-line utility for digitally signing and verifying a file.
 *
 * <p>It loads cleartext keys from disk - this is not recommended!
 *
 * <p>It requires the following arguments:
 *
 * <ul>
 *   <li>mode: either 'sign' or 'verify'.
 *   <li>key-file: Read the key material from this file.
 *   <li>input-file: Read the input from this file.
 *   <li>signature-file: name of the file containing a hexadecimal signature of the input file.
 */
public final class SignatureExample {
  public static void main(String[] args) throws Exception {
    if (args.length != 4) {
      System.err.printf("Expected 4 parameters, got %d\n", args.length);
      System.err.println(
          "Usage: java SignatureExample sign/verify key-file input-file signature-file");
      System.exit(1);
    }

    String mode = args[0];
    if (!mode.equals("sign") && !mode.equals("verify")) {
      System.err.println("Incorrect mode. Please select sign or verify.");
      System.exit(1);
    }
    Path keyFile = Paths.get(args[1]);
    byte[] msg = Files.readAllBytes(Paths.get(args[2]));
    Path signatureFile = Paths.get(args[3]);

    // Register all signature key types with the Tink runtime.
    SignatureConfig.register();

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

    if (mode.equals("sign")) {
      // Get the primitive.
      PublicKeySign signer = handle.getPrimitive(RegistryConfiguration.get(), PublicKeySign.class);

      // Use the primitive to sign data.
      byte[] signature = signer.sign(msg);
      Files.write(signatureFile, signature);
    } else {
      byte[] signature = Files.readAllBytes(signatureFile);

      // Get the primitive.
      PublicKeyVerify verifier =
          handle.getPrimitive(RegistryConfiguration.get(), PublicKeyVerify.class);

      verifier.verify(signature, msg);
    }
  }

  private SignatureExample() {}
}
SignatureExample.java

PETUNJUK

import tink
from tink import secret_key_access
from tink import signature


def example():
  """Sign and verify using digital signatures."""
  # Register the signature key managers. This is needed to create
  # PublicKeySign and PublicKeyVerify primitives later.
  signature.register()

  # A private keyset created with
  # "tinkey create-keyset --key-template=ECDSA_P256 --out private_keyset.cfg".
  # Note that this keyset has the secret key information in cleartext.
  private_keyset = r"""{
      "key": [{
          "keyData": {
              "keyMaterialType":
                  "ASYMMETRIC_PRIVATE",
              "typeUrl":
                  "type.googleapis.com/google.crypto.tink.EcdsaPrivateKey",
              "value":
                  "EkwSBggDEAIYAhogEiSZ9u2nDtvZuDgWgGsVTIZ5/V08N4ycUspTX0RYRrkiIHpEwHxQd1bImkyMvV2bqtUbgMh5uPSTdnUEGrPXdt56GiEA3iUi+CRN71qy0fOCK66xAW/IvFyjOGtxjppRhSFUneo="
          },
          "keyId": 611814836,
          "outputPrefixType": "TINK",
          "status": "ENABLED"
      }],
      "primaryKeyId": 611814836
  }"""

  # The corresponding public keyset created with
  # "tinkey create-public-keyset --in private_keyset.cfg"
  public_keyset = r"""{
      "key": [{
          "keyData": {
              "keyMaterialType":
                  "ASYMMETRIC_PUBLIC",
              "typeUrl":
                  "type.googleapis.com/google.crypto.tink.EcdsaPublicKey",
              "value":
                  "EgYIAxACGAIaIBIkmfbtpw7b2bg4FoBrFUyGef1dPDeMnFLKU19EWEa5IiB6RMB8UHdWyJpMjL1dm6rVG4DIebj0k3Z1BBqz13beeg=="
          },
          "keyId": 611814836,
          "outputPrefixType": "TINK",
          "status": "ENABLED"
      }],
      "primaryKeyId": 611814836
  }"""

  # 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 tink.json_proto_keyset_format.parse, as
  # it implies that your key material is passed in cleartext which is a security
  # risk.
  private_keyset_handle = tink.json_proto_keyset_format.parse(
      private_keyset, secret_key_access.TOKEN
  )

  # Retrieve the PublicKeySign primitive we want to use from the keyset
  # handle.
  sign_primitive = private_keyset_handle.primitive(signature.PublicKeySign)

  # Use the primitive to sign a message. In this case the primary key of the
  # keyset will be used (which is also the only key in this example).
  sig = sign_primitive.sign(b'msg')

  # Create a keyset handle from the keyset containing the public key. Because
  # this keyset does not contain any secrets, we can use
  # `parse_without_secret`.
  public_keyset_handle = tink.json_proto_keyset_format.parse_without_secret(
      public_keyset
  )

  # Retrieve the PublicKeyVerify primitive we want to use from the keyset
  # handle.
  verify_primitive = public_keyset_handle.primitive(signature.PublicKeyVerify)

  # Use the primitive to verify that `sig` is valid signature for the message.
  # Verify finds the correct key in the keyset. If no key is found or
  # verification fails, it raises an error.
  verify_primitive.verify(sig, b'msg')

  # Note that we can also get the public keyset handle from the private keyset
  # handle. The verification works the same as above.
  public_keyset_handle2 = private_keyset_handle.public_keyset_handle()
  verify_primitive2 = public_keyset_handle2.primitive(signature.PublicKeyVerify)
  verify_primitive2.verify(sig, b'msg')
signature_basic.py

Tanda Tangan Digital

Primitif Tanda Tangan Digital memungkinkan Anda memverifikasi bahwa tidak ada orang yang telah memodifikasi data Anda. Hal ini memberikan keaslian dan integritas, tetapi bukan kerahasiaan, data yang ditandatangani. Enkripsi ini bersifat asimetris, yang berarti menggunakan sepasang kunci (kunci publik dan kunci pribadi).

Primitif Tanda Tangan Digital memiliki properti berikut:

• Keaslian: Anda tidak dapat membuat tanda tangan yang divalidasi oleh PublicKeyVerify.Verify(signature, message), kecuali jika Anda memiliki kunci pribadi.
• Asimetris: Membuat tanda tangan menggunakan kunci yang berbeda dengan verifikasinya. Hal ini memungkinkan Anda mendistribusikan kunci publik untuk memverifikasi tanda tangan kepada pihak yang tidak dapat membuat tanda tangan sendiri.

Jika Anda tidak memerlukan asimetri, sebaiknya gunakan primitif MAC yang lebih sederhana dan lebih efisien.

Fungsi tanda tangan digital direpresentasikan di Tink sebagai sepasang primitif:

• PublicKeySign untuk menandatangani data
• PublicKeyVerify untuk memverifikasi tanda tangan

Memilih jenis kunci

Sebaiknya gunakan ECDSA_P256 untuk sebagian besar kasus penggunaan, tetapi ada berbagai opsi. Secara umum, hal berikut berlaku:

• ECDSA_P256 adalah opsi yang paling banyak digunakan dan merupakan setelan default yang wajar. Namun, perhatikan bahwa tanda tangan ECDSA dapat diubah.
• ED25519 membuat tanda tangan deterministik dan memberikan performa yang lebih baik daripada ECDSA_P256.
• RSA_SSA_PKCS1_3072_SHA256_F4 membuat tanda tangan deterministik dan memberikan performa verifikasi terbaik (tetapi penandatanganan jauh lebih lambat daripada ECDSA_P256 atau ED25519).

Jaminan keamanan minimum

• Data yang akan ditandatangani dapat memiliki panjang arbitrer
• Tingkat keamanan 128-bit terhadap serangan pesan pilihan adaptif untuk skema berbasis kurva elips
• Tingkat keamanan 112-bit terhadap serangan pesan pilihan adaptif untuk skema berbasis RSA (memungkinkan kunci 2048-bit)

Kelenturan

Skema tanda tangan dapat diubah jika penyerang dapat membuat tanda tangan valid yang berbeda untuk pesan yang sudah ditandatangani. Meskipun hal ini bukan masalah untuk sebagian besar skenario, dalam beberapa kasus, programmer secara implisit mengasumsikan bahwa tanda tangan yang valid adalah unik, dan hal ini dapat menyebabkan hasil yang tidak terduga.