Voglio firmare i dati digitalmente

Per la maggior parte dei casi d'uso, consigliamo l'elemento primitivo Firma digitale con tipo di chiave ECDSA_P256.

La primitiva della firma digitale garantisce che nessuno abbia manomesso i tuoi dati e ne dimostra la provenienza. È asimmetrica, in quanto utilizza la chiave privata per firmare i dati e la chiave pubblica per verificarli.

Gli esempi riportati di seguito ti consentono di iniziare a utilizzare la primitiva Firma digitale:

C++VaiJavaObj-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

GUIDA ILLUSTRATIVA

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

Firma digitale

La primitiva Firma digitale ti consente di verificare che nessuno abbia manomesso i tuoi dati. Garantisce l'autenticità e l'integrità, ma non la segretezza, dei dati firmati. È asimmetrica, il che significa che utilizza una coppia di chiavi (chiave pubblica e chiave privata).

La primitiva Firma digitale ha le seguenti proprietà:

• Autenticità: è impossibile creare una firma per la quale PublicKeyVerify.Verify(signature, message) convalida, a meno che tu non abbia la chiave privata.
• Asimmetrica: per creare la firma viene utilizzata una chiave diversa da quella utilizzata per verificarla. In questo modo puoi distribuire la chiave pubblica per la verifica delle firme a terze parti che non possono creare le firme.

Se non hai bisogno di asimmetria, valuta la possibilità di utilizzare la primitiva MAC, più semplice ed efficiente.

La funzionalità delle firme digitali è rappresentata in Tink come una coppia di primitive:

• PublicKeySign per la firma dei dati
• PublicKeyVerify per la verifica della firma

Scegli un tipo di chiave

Consigliamo di utilizzare ECDSA_P256 per la maggior parte dei casi d'uso, ma sono disponibili diverse opzioni. In generale, vale quanto segue:

• ECDSA_P256 è l'opzione più utilizzata e un valore predefinito ragionevole. Tieni tuttavia presente che le firme ECDSA sono malleabili.
• ED25519 crea firme deterministiche e offre prestazioni migliori rispetto a ECDSA_P256.
• RSA_SSA_PKCS1_3072_SHA256_F4 crea firme deterministiche e offre il miglior rendimento di verifica (ma la firma è molto più lenta di ECDSA_P256 o ED25519).

Garanzie di sicurezza minime

• I dati da firmare possono avere una lunghezza arbitraria
• Livello di sicurezza di 128 bit contro gli attacchi adattivi con messaggio scelto per i schemi basati su curve ellittiche
• Livello di sicurezza di 112 bit contro gli attacchi adattivi con messaggio scelto per i metodi basati su RSA (consente chiavi a 2048 bit)

Duttilità

Uno schema di firma è malleabile se un malintenzionato può creare una firma valida diversa per un messaggio già firmato. Sebbene questo non sia un problema per la maggior parte degli scenari, in alcuni casi i programmatori presumono implicitamente che le firme valide siano univoche e questo può portare a risultati imprevisti.