Crittografia e decriptazione dei dati con una chiave asimmetrica

Questo argomento fornisce informazioni sulla creazione e sull'utilizzo di una chiave per asimmetrica con una chiave RSA. Se vuoi utilizzare chiavi asimmetriche per creare e convalidare le firme, consulta Creazione e convalida delle firme digitali. Se vuoi utilizzare chiavi simmetriche per la crittografia e la decrittografia, consulta Crittografia e decriptazione dei dati.

La crittografia asimmetrica utilizza la parte della chiave pubblica della chiave asimmetrica e la decrittografia utilizza la parte della chiave privata della chiave. Cloud Key Management Service fornisce funzionalità per recuperare la chiave pubblica e funzionalità per decriptare testo crittografato che è stato criptato con la chiave pubblica. Cloud KMS non consente l'accesso diretto alla chiave privata.

Prima di iniziare

  • Questo argomento fornisce esempi che vengono eseguiti nella riga di comando. Per semplificare l'utilizzo gli esempi, utilizza Cloud Shell. L'esempio di crittografia utilizza OpenSSL, che è preinstallato su Cloud Shell.

  • Crea una chiave asimmetrica con lo scopo della chiave ASYMMETRIC_DECRYPT. Per vedere quali algoritmi sono supportati per lo scopo chiave ASYMMETRIC_DECRYPT, consulta Algoritmi di crittografia asimmetrici. Non puoi seguire questa procedura con una chiave con scopo di ASYMMETRIC_SIGN.

  • Se intendi utilizzare la riga di comando, installa OpenSSL se non lo hai già. Se utilizzi Cloud Shell, OpenSSL è già installato.

  • Utenti macOS: La versione di OpenSSL installata su macOS non supporta i flag utilizzati per decriptare i dati in questo argomento. Per seguire questi passaggi su macOS, installa OpenSSL da Homebrew.

Controllo dell'accesso alla chiave

  • Per un utente o un servizio che recupererà la chiave pubblica, concedi il metodo Autorizzazione cloudkms.cryptoKeyVersions.viewPublicKey per la chiave asimmetrica. La chiave pubblica è necessaria per criptare i dati.

  • Per un utente o un servizio che decripta i dati criptati con chiave pubblica, concedi l'autorizzazione cloudkms.cryptoKeyVersions.useToDecrypt su la chiave asimmetrica.

Per saperne di più sulle autorizzazioni e sui ruoli in Cloud KMS, consulta la pagina Autorizzazioni e ruoli.

Criptare i dati

Per criptare i dati utilizzando una chiave di crittografia asimmetrica, recupera la chiave pubblica e utilizzala per criptare i dati.

gcloud

Questo esempio richiede che OpenSSL sia installato sul sistema locale.

Scarica chiave pubblica

Scarica la chiave pubblica:

gcloud kms keys versions get-public-key key-version \
    --key key \
    --keyring key-ring \
    --location location  \
    --output-file public-key-path

Sostituisci key-version con la versione della chiave che include la chiave pubblica. Sostituisci key con il nome della chiave. Sostituisci key-ring con il nome del mazzo di chiavi in cui si trova la chiave. Sostituisci location con la località di Cloud KMS per l'account il keyring. Sostituisci public-key-path con la posizione in cui salvare la chiave pubblica sul sistema locale.

Cripta i dati

Cripta i dati utilizzando la chiave pubblica appena scaricata e salva l'output in un file:

openssl pkeyutl -in cleartext-data-input-file \
    -encrypt \
    -pubin \
    -inkey public-key-path \
    -pkeyopt rsa_padding_mode:oaep \
    -pkeyopt rsa_oaep_md:sha256 \
    -pkeyopt rsa_mgf1_md:sha256 \
    > encrypted-data-output-file

  • Sostituisci cleartext-data-input-file con il percorso e il nome file da criptare.

  • Sostituisci public-key-path con il percorso e il nome del file in cui scaricato la chiave pubblica.

  • Sostituisci encrypted-data-output-file con il percorso e il nome del file per salvare i dati criptati.

C#

Per eseguire questo codice, devi innanzitutto configurare un ambiente di sviluppo C# e installare l'SDK C# Cloud KMS.


using Google.Cloud.Kms.V1;
using System;
using System.Security.Cryptography;
using System.Text;

public class EncryptAsymmetricSample
{
    public byte[] EncryptAsymmetric(
      string projectId = "my-project", string locationId = "us-east1", string keyRingId = "my-key-ring", string keyId = "my-key", string keyVersionId = "123",
      string message = "Sample message")
    {
        // Create the client.
        KeyManagementServiceClient client = KeyManagementServiceClient.Create();

        // Build the key version name.
        CryptoKeyVersionName keyVersionName = new CryptoKeyVersionName(projectId, locationId, keyRingId, keyId, keyVersionId);

        // Get the public key.
        PublicKey publicKey = client.GetPublicKey(keyVersionName);

        // Split the key into blocks and base64-decode the PEM parts.
        string[] blocks = publicKey.Pem.Split("-", StringSplitOptions.RemoveEmptyEntries);
        byte[] pem = Convert.FromBase64String(blocks[1]);

        // Create a new RSA key.
        RSA rsa = RSA.Create();
        rsa.ImportSubjectPublicKeyInfo(pem, out _);

        // Convert the message into bytes. Cryptographic plaintexts and
        // ciphertexts are always byte arrays.
        byte[] plaintext = Encoding.UTF8.GetBytes(message);

        // Encrypt the data.
        byte[] ciphertext = rsa.Encrypt(plaintext, RSAEncryptionPadding.OaepSHA256);
        return ciphertext;
    }
}

Go

Per utilizzare Cloud KMS sulla riga di comando, innanzitutto esegui l'installazione o l'upgrade alla versione più recente di Google Cloud CLI.

import (
	"context"
	"crypto/rand"
	"crypto/rsa"
	"crypto/sha256"
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"io"

	kms "cloud.google.com/go/kms/apiv1"
	"cloud.google.com/go/kms/apiv1/kmspb"
)

// encryptAsymmetric encrypts data on your local machine using an
// 'RSA_DECRYPT_OAEP_2048_SHA256' public key retrieved from Cloud KMS.
func encryptAsymmetric(w io.Writer, name string, message string) error {
	// name := "projects/my-project/locations/us-east1/keyRings/my-key-ring/cryptoKeys/my-key/cryptoKeyVersions/123"
	// message := "Sample message"

	// Create the client.
	ctx := context.Background()
	client, err := kms.NewKeyManagementClient(ctx)
	if err != nil {
		return fmt.Errorf("failed to create kms client: %w", err)
	}
	defer client.Close()

	// Retrieve the public key from Cloud KMS. This is the only operation that
	// involves Cloud KMS. The remaining operations take place on your local
	// machine.
	response, err := client.GetPublicKey(ctx, &kmspb.GetPublicKeyRequest{
		Name: name,
	})
	if err != nil {
		return fmt.Errorf("failed to get public key: %w", err)
	}

	// Parse the public key. Note, this example assumes the public key is in the
	// RSA format.
	block, _ := pem.Decode([]byte(response.Pem))
	publicKey, err := x509.ParsePKIXPublicKey(block.Bytes)
	if err != nil {
		return fmt.Errorf("failed to parse public key: %w", err)
	}
	rsaKey, ok := publicKey.(*rsa.PublicKey)
	if !ok {
		return fmt.Errorf("public key is not rsa")
	}

	// Convert the message into bytes. Cryptographic plaintexts and
	// ciphertexts are always byte arrays.
	plaintext := []byte(message)

	// Encrypt data using the RSA public key.
	ciphertext, err := rsa.EncryptOAEP(sha256.New(), rand.Reader, rsaKey, plaintext, nil)
	if err != nil {
		return fmt.Errorf("rsa.EncryptOAEP: %w", err)
	}
	fmt.Fprintf(w, "Encrypted ciphertext: %s", ciphertext)
	return nil
}

Java

Per eseguire questo codice, per prima cosa configura un ambiente di sviluppo Java e installare l'SDK Java di Cloud KMS.

import com.google.cloud.kms.v1.CryptoKeyVersionName;
import com.google.cloud.kms.v1.KeyManagementServiceClient;
import com.google.cloud.kms.v1.PublicKey;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.StringReader;
import java.nio.charset.StandardCharsets;
import java.security.GeneralSecurityException;
import java.security.KeyFactory;
import java.security.spec.MGF1ParameterSpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
import java.util.stream.Collectors;
import javax.crypto.Cipher;
import javax.crypto.spec.OAEPParameterSpec;
import javax.crypto.spec.PSource;

public class EncryptAsymmetric {

  public void encryptAsymmetric() throws IOException, GeneralSecurityException {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "your-project-id";
    String locationId = "us-east1";
    String keyRingId = "my-key-ring";
    String keyId = "my-key";
    String keyVersionId = "123";
    String plaintext = "Plaintext to encrypt";
    encryptAsymmetric(projectId, locationId, keyRingId, keyId, keyVersionId, plaintext);
  }

  // Encrypt data that was encrypted using the public key component of the given
  // key version.
  public void encryptAsymmetric(
      String projectId,
      String locationId,
      String keyRingId,
      String keyId,
      String keyVersionId,
      String plaintext)
      throws IOException, GeneralSecurityException {
    // Initialize client that will be used to send requests. This client only
    // needs to be created once, and can be reused for multiple requests. After
    // completing all of your requests, call the "close" method on the client to
    // safely clean up any remaining background resources.
    try (KeyManagementServiceClient client = KeyManagementServiceClient.create()) {
      // Build the key version name from the project, location, key ring, key,
      // and key version.
      CryptoKeyVersionName keyVersionName =
          CryptoKeyVersionName.of(projectId, locationId, keyRingId, keyId, keyVersionId);

      // Get the public key.
      PublicKey publicKey = client.getPublicKey(keyVersionName);

      // Convert the public PEM key to a DER key (see helper below).
      byte[] derKey = convertPemToDer(publicKey.getPem());
      X509EncodedKeySpec keySpec = new X509EncodedKeySpec(derKey);
      java.security.PublicKey rsaKey = KeyFactory.getInstance("RSA").generatePublic(keySpec);

      // Encrypt plaintext for the 'RSA_DECRYPT_OAEP_2048_SHA256' key.
      // For other key algorithms:
      // https://docs.oracle.com/javase/7/docs/api/javax/crypto/Cipher.html
      Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPWithSHA-256AndMGF1Padding");
      OAEPParameterSpec oaepParams =
          new OAEPParameterSpec(
              "SHA-256", "MGF1", MGF1ParameterSpec.SHA256, PSource.PSpecified.DEFAULT);
      cipher.init(Cipher.ENCRYPT_MODE, rsaKey, oaepParams);
      byte[] ciphertext = cipher.doFinal(plaintext.getBytes(StandardCharsets.UTF_8));
      System.out.printf("Ciphertext: %s%n", ciphertext);
    }
  }

  // Converts a base64-encoded PEM certificate like the one returned from Cloud
  // KMS into a DER formatted certificate for use with the Java APIs.
  private byte[] convertPemToDer(String pem) {
    BufferedReader bufferedReader = new BufferedReader(new StringReader(pem));
    String encoded =
        bufferedReader
            .lines()
            .filter(line -> !line.startsWith("-----BEGIN") && !line.startsWith("-----END"))
            .collect(Collectors.joining());
    return Base64.getDecoder().decode(encoded);
  }
}

Node.js

Per eseguire questo codice, devi innanzitutto configurare un ambiente di sviluppo Node.js e installare l'SDK Node.js di Cloud KMS.

//
// TODO(developer): Uncomment these variables before running the sample.
//
// const projectId = 'my-project';
// const locationId = 'us-east1';
// const keyRingId = 'my-key-ring';
// const keyId = 'my-key';
// const versionId = '123';
// const plaintextBuffer = Buffer.from('...');

// Imports the Cloud KMS library
const {KeyManagementServiceClient} = require('@google-cloud/kms');

// Instantiates a client
const client = new KeyManagementServiceClient();

// Build the key version name
const versionName = client.cryptoKeyVersionPath(
  projectId,
  locationId,
  keyRingId,
  keyId,
  versionId
);

async function encryptAsymmetric() {
  // Get public key from Cloud KMS
  const [publicKey] = await client.getPublicKey({
    name: versionName,
  });

  // Optional, but recommended: perform integrity verification on publicKey.
  // For more details on ensuring E2E in-transit integrity to and from Cloud KMS visit:
  // https://cloud.google.com/kms/docs/data-integrity-guidelines
  const crc32c = require('fast-crc32c');
  if (publicKey.name !== versionName) {
    throw new Error('GetPublicKey: request corrupted in-transit');
  }
  if (crc32c.calculate(publicKey.pem) !== Number(publicKey.pemCrc32c.value)) {
    throw new Error('GetPublicKey: response corrupted in-transit');
  }

  // Import and setup crypto
  const crypto = require('crypto');

  // Encrypt plaintext locally using the public key. This example uses a key
  // that was configured with sha256 hash with OAEP padding. Update these
  // values to match the Cloud KMS key.
  //
  // NOTE: In Node < 12, this function does not properly consume the OAEP
  // padding and thus produces invalid ciphertext. If you are using Node to do
  // public key encryption, please use version 12+.
  const ciphertextBuffer = crypto.publicEncrypt(
    {
      key: publicKey.pem,
      oaepHash: 'sha256',
      padding: crypto.constants.RSA_PKCS1_OAEP_PADDING,
    },
    plaintextBuffer
  );

  console.log(`Ciphertext: ${ciphertextBuffer.toString('base64')}`);
  return ciphertextBuffer;
}

return encryptAsymmetric();

PHP

Per eseguire questo codice, scopri innanzitutto come utilizzare PHP su Google Cloud e installa l'SDK PHP di Cloud KMS.

function encrypt_asymmetric(
    string $projectId = 'my-project',
    string $locationId = 'us-east1',
    string $keyRingId = 'my-key-ring',
    string $keyId = 'my-key',
    string $versionId = '123',
    string $plaintext = '...'
): void {
    // PHP has limited support for asymmetric encryption operations.
    // Specifically, openssl_public_encrypt() does not allow customizing
    // algorithms or padding. Thus, it is not currently possible to use PHP
    // core for asymmetric operations on RSA keys.
    //
    // Third party libraries like phpseclib may provide the required
    // functionality. Google does not endorse this external library.
}

Python

Per eseguire questo codice, configura prima un ambiente di sviluppo Python e installare l'SDK per Python di Cloud KMS.


# Import base64 for printing the ciphertext.
import base64

# Import cryptographic helpers from the cryptography package.
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import padding

# Import the client library.
from google.cloud import kms


def encrypt_asymmetric(
    project_id: str,
    location_id: str,
    key_ring_id: str,
    key_id: str,
    version_id: str,
    plaintext: str,
) -> bytes:
    """
    Encrypt plaintext using the public key portion of an asymmetric key.

    Args:
        project_id (string): Google Cloud project ID (e.g. 'my-project').
        location_id (string): Cloud KMS location (e.g. 'us-east1').
        key_ring_id (string): ID of the Cloud KMS key ring (e.g. 'my-key-ring').
        key_id (string): ID of the key to use (e.g. 'my-key').
        version_id (string): ID of the key version to use (e.g. '1').
        plaintext (string): message to encrypt

    Returns:
        bytes: Encrypted ciphertext.

    """

    # Convert the plaintext to bytes.
    plaintext_bytes = plaintext.encode("utf-8")

    # Create the client.
    client = kms.KeyManagementServiceClient()

    # Build the key version name.
    key_version_name = client.crypto_key_version_path(
        project_id, location_id, key_ring_id, key_id, version_id
    )

    # Get the public key.
    public_key = client.get_public_key(request={"name": key_version_name})

    # Extract and parse the public key as a PEM-encoded RSA key.
    pem = public_key.pem.encode("utf-8")
    rsa_key = serialization.load_pem_public_key(pem, default_backend())

    # Construct the padding. Note that the padding differs based on key choice.
    sha256 = hashes.SHA256()
    mgf = padding.MGF1(algorithm=sha256)
    pad = padding.OAEP(mgf=mgf, algorithm=sha256, label=None)

    # Encrypt the data using the public key.
    ciphertext = rsa_key.encrypt(plaintext_bytes, pad)
    print(f"Ciphertext: {base64.b64encode(ciphertext)!r}")
    return ciphertext

Ruby

Per eseguire questo codice, prima configura un ambiente di sviluppo Ruby e installa l'SDK Ruby di Cloud KMS.

# Ruby has limited support for asymmetric encryption operations. Specifically,
# public_encrypt() does not allow customizing the MGF hash algorithm. Thus, it
# is not currently possible to use Ruby core for asymmetric encryption
# operations on RSA keys from Cloud KMS.
#
# Third party libraries may provide the required functionality. Google does
# not endorse these external libraries.

Decriptare i dati

Utilizza Cloud KMS per eseguire la decriptazione.

gcloud

Per utilizzare Cloud KMS nella riga di comando, devi prima Installa o esegui l'upgrade alla versione più recente di Google Cloud CLI.

gcloud kms asymmetric-decrypt \
    --version key-version \
    --key key \
    --keyring key-ring \
    --location location  \
    --ciphertext-file file-path-with-encrypted-data \
    --plaintext-file file-path-to-store-plaintext

Sostituisci key-version con la versione della chiave o ometti il flag --version per rilevare automaticamente la versione. Sostituisci key con il nome della chiave da utilizzare per la decrittografia. Sostituisci key-ring con il nome del mazzo di chiavi in cui si troverà la chiave. Sostituisci location con la posizione Cloud KMS per il keyring. Sostituisci file-path-with-encrypted-data e file-path-to-store-plaintext con i percorsi dei file locali per la lettura dei dati criptati e il salvataggio dei file come output.

Per informazioni su tutti i flag e i possibili valori, esegui il comando con il flag --help.

Per visualizzare i contenuti del file decriptato, apri il file nell'editor o nel terminale. Ecco un esempio che mostra i contenuti del file utilizzando l'istruzione cat :

cat ./my-file.txt

C#

Per eseguire questo codice, per prima cosa configura un ambiente di sviluppo C# e installare l'SDK Cloud KMS C#.


using Google.Cloud.Kms.V1;
using Google.Protobuf;
using System.Text;

public class DecryptAsymmetricSample
{
    public string DecryptAsymmetric(
      string projectId = "my-project", string locationId = "us-east1", string keyRingId = "my-key-ring", string keyId = "my-key", string keyVersionId = "123",
      byte[] ciphertext = null)
    {
        // Create the client.
        KeyManagementServiceClient client = KeyManagementServiceClient.Create();

        // Build the key version name.
        CryptoKeyVersionName keyVersionName = new CryptoKeyVersionName(projectId, locationId, keyRingId, keyId, keyVersionId);

        // Call the API.
        AsymmetricDecryptResponse result = client.AsymmetricDecrypt(keyVersionName, ByteString.CopyFrom(ciphertext));

        // Get the plaintext. Cryptographic plaintexts and ciphertexts are
        // always byte arrays.
        byte[] plaintext = result.Plaintext.ToByteArray();

        // Return the result.
        return Encoding.UTF8.GetString(plaintext);
    }
}

Go

Per eseguire questo codice, devi innanzitutto configurare un ambiente di sviluppo Go e installare l'SDK Go Cloud KMS.

import (
	"context"
	"fmt"
	"hash/crc32"
	"io"

	kms "cloud.google.com/go/kms/apiv1"
	"cloud.google.com/go/kms/apiv1/kmspb"
	"google.golang.org/protobuf/types/known/wrapperspb"
)

// decryptAsymmetric will attempt to decrypt a given ciphertext with an
// 'RSA_DECRYPT_OAEP_2048_SHA256' key from Cloud KMS.
func decryptAsymmetric(w io.Writer, name string, ciphertext []byte) error {
	// name := "projects/my-project/locations/us-east1/keyRings/my-key-ring/cryptoKeys/my-key/cryptoKeyVersions/123"
	// ciphertext := []byte("...")  // result of an asymmetric encryption call

	// Create the client.
	ctx := context.Background()
	client, err := kms.NewKeyManagementClient(ctx)
	if err != nil {
		return fmt.Errorf("failed to create kms client: %w", err)
	}
	defer client.Close()

	// Optional but recommended: Compute ciphertext's CRC32C.
	crc32c := func(data []byte) uint32 {
		t := crc32.MakeTable(crc32.Castagnoli)
		return crc32.Checksum(data, t)
	}
	ciphertextCRC32C := crc32c(ciphertext)

	// Build the request.
	req := &kmspb.AsymmetricDecryptRequest{
		Name:             name,
		Ciphertext:       ciphertext,
		CiphertextCrc32C: wrapperspb.Int64(int64(ciphertextCRC32C)),
	}

	// Call the API.
	result, err := client.AsymmetricDecrypt(ctx, req)
	if err != nil {
		return fmt.Errorf("failed to decrypt ciphertext: %w", err)
	}

	// Optional, but recommended: perform integrity verification on result.
	// For more details on ensuring E2E in-transit integrity to and from Cloud KMS visit:
	// https://cloud.google.com/kms/docs/data-integrity-guidelines
	if result.VerifiedCiphertextCrc32C == false {
		return fmt.Errorf("AsymmetricDecrypt: request corrupted in-transit")
	}
	if int64(crc32c(result.Plaintext)) != result.PlaintextCrc32C.Value {
		return fmt.Errorf("AsymmetricDecrypt: response corrupted in-transit")
	}

	fmt.Fprintf(w, "Decrypted plaintext: %s", result.Plaintext)
	return nil
}

Java

Per eseguire questo codice, devi innanzitutto configurare un ambiente di sviluppo Java e installare l'SDK Java Cloud KMS.

import com.google.cloud.kms.v1.AsymmetricDecryptResponse;
import com.google.cloud.kms.v1.CryptoKeyVersionName;
import com.google.cloud.kms.v1.KeyManagementServiceClient;
import com.google.protobuf.ByteString;
import java.io.IOException;

public class DecryptAsymmetric {

  public void decryptAsymmetric() throws IOException {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "your-project-id";
    String locationId = "us-east1";
    String keyRingId = "my-key-ring";
    String keyId = "my-key";
    String keyVersionId = "123";
    byte[] ciphertext = null;
    decryptAsymmetric(projectId, locationId, keyRingId, keyId, keyVersionId, ciphertext);
  }

  // Decrypt data that was encrypted using the public key component of the given
  // key version.
  public void decryptAsymmetric(
      String projectId,
      String locationId,
      String keyRingId,
      String keyId,
      String keyVersionId,
      byte[] ciphertext)
      throws IOException {
    // Initialize client that will be used to send requests. This client only
    // needs to be created once, and can be reused for multiple requests. After
    // completing all of your requests, call the "close" method on the client to
    // safely clean up any remaining background resources.
    try (KeyManagementServiceClient client = KeyManagementServiceClient.create()) {
      // Build the key version name from the project, location, key ring, key,
      // and key version.
      CryptoKeyVersionName keyVersionName =
          CryptoKeyVersionName.of(projectId, locationId, keyRingId, keyId, keyVersionId);

      // Decrypt the ciphertext.
      AsymmetricDecryptResponse response =
          client.asymmetricDecrypt(keyVersionName, ByteString.copyFrom(ciphertext));
      System.out.printf("Plaintext: %s%n", response.getPlaintext().toStringUtf8());
    }
  }
}

Node.js

Per eseguire questo codice, devi prima configurare un ambiente di sviluppo Node.js e installare l'SDK Node.js di Cloud KMS.

//
// TODO(developer): Uncomment these variables before running the sample.
//
// const projectId = 'my-project';
// const locationId = 'us-east1';
// const keyRingId = 'my-key-ring';
// const keyId = 'my-key';
// const versionId = '123';
// const ciphertext = Buffer.from('...');

// Imports the Cloud KMS library
const {KeyManagementServiceClient} = require('@google-cloud/kms');

// Instantiates a client
const client = new KeyManagementServiceClient();

// Build the key version name
const versionName = client.cryptoKeyVersionPath(
  projectId,
  locationId,
  keyRingId,
  keyId,
  versionId
);

// Optional, but recommended: compute plaintext's CRC32C.
const crc32c = require('fast-crc32c');
const ciphertextCrc32c = crc32c.calculate(ciphertext);

async function decryptAsymmetric() {
  const [decryptResponse] = await client.asymmetricDecrypt({
    name: versionName,
    ciphertext: ciphertext,
    ciphertextCrc32c: {
      value: ciphertextCrc32c,
    },
  });

  // Optional, but recommended: perform integrity verification on decryptResponse.
  // For more details on ensuring E2E in-transit integrity to and from Cloud KMS visit:
  // https://cloud.google.com/kms/docs/data-integrity-guidelines
  if (!decryptResponse.verifiedCiphertextCrc32c) {
    throw new Error('AsymmetricDecrypt: request corrupted in-transit');
  }
  if (
    crc32c.calculate(decryptResponse.plaintext) !==
    Number(decryptResponse.plaintextCrc32c.value)
  ) {
    throw new Error('AsymmetricDecrypt: response corrupted in-transit');
  }

  // NOTE: The ciphertext must be properly formatted. In Node < 12, the
  // crypto.publicEncrypt() function does not properly consume the OAEP
  // padding and thus produces invalid ciphertext. If you are using Node to do
  // public key encryption, please use version 12+.
  const plaintext = decryptResponse.plaintext.toString('utf8');

  console.log(`Plaintext: ${plaintext}`);
  return plaintext;
}

return decryptAsymmetric();

PHP

Per eseguire questo codice, devi innanzitutto scoprire come utilizzare PHP su Google Cloud e installare l'SDK PHP Cloud KMS.

use Google\Cloud\Kms\V1\AsymmetricDecryptRequest;
use Google\Cloud\Kms\V1\Client\KeyManagementServiceClient;

function decrypt_asymmetric(
    string $projectId = 'my-project',
    string $locationId = 'us-east1',
    string $keyRingId = 'my-key-ring',
    string $keyId = 'my-key',
    string $versionId = '123',
    string $ciphertext = '...'
) {
    // Create the Cloud KMS client.
    $client = new KeyManagementServiceClient();

    // Build the key version name.
    $keyVersionName = $client->cryptoKeyVersionName($projectId, $locationId, $keyRingId, $keyId, $versionId);

    // Call the API.
    $asymmetricDecryptRequest = (new AsymmetricDecryptRequest())
        ->setName($keyVersionName)
        ->setCiphertext($ciphertext);
    $decryptResponse = $client->asymmetricDecrypt($asymmetricDecryptRequest);
    printf('Plaintext: %s' . PHP_EOL, $decryptResponse->getPlaintext());

    return $decryptResponse;
}

Python

Per eseguire questo codice, devi innanzitutto configurare un ambiente di sviluppo Python e installare l'SDK Python Cloud KMS.

from google.cloud import kms


def decrypt_asymmetric(
    project_id: str,
    location_id: str,
    key_ring_id: str,
    key_id: str,
    version_id: str,
    ciphertext: bytes,
) -> kms.DecryptResponse:
    """
    Decrypt the ciphertext using an asymmetric key.

    Args:
        project_id (string): Google Cloud project ID (e.g. 'my-project').
        location_id (string): Cloud KMS location (e.g. 'us-east1').
        key_ring_id (string): ID of the Cloud KMS key ring (e.g. 'my-key-ring').
        key_id (string): ID of the key to use (e.g. 'my-key').
        version_id (string): ID of the key version to use (e.g. '1').
        ciphertext (bytes): Encrypted bytes to decrypt.

    Returns:
        DecryptResponse: Response including plaintext.

    """

    # Create the client.
    client = kms.KeyManagementServiceClient()

    # Build the key version name.
    key_version_name = client.crypto_key_version_path(
        project_id, location_id, key_ring_id, key_id, version_id
    )

    # Optional, but recommended: compute ciphertext's CRC32C.
    # See crc32c() function defined below.
    ciphertext_crc32c = crc32c(ciphertext)

    # Call the API.
    decrypt_response = client.asymmetric_decrypt(
        request={
            "name": key_version_name,
            "ciphertext": ciphertext,
            "ciphertext_crc32c": ciphertext_crc32c,
        }
    )

    # Optional, but recommended: perform integrity verification on decrypt_response.
    # For more details on ensuring E2E in-transit integrity to and from Cloud KMS visit:
    # https://cloud.google.com/kms/docs/data-integrity-guidelines
    if not decrypt_response.verified_ciphertext_crc32c:
        raise Exception("The request sent to the server was corrupted in-transit.")
    if not decrypt_response.plaintext_crc32c == crc32c(decrypt_response.plaintext):
        raise Exception(
            "The response received from the server was corrupted in-transit."
        )
    # End integrity verification

    print(f"Plaintext: {decrypt_response.plaintext!r}")
    return decrypt_response


def crc32c(data: bytes) -> int:
    """
    Calculates the CRC32C checksum of the provided data.
    Args:
        data: the bytes over which the checksum should be calculated.
    Returns:
        An int representing the CRC32C checksum of the provided bytes.
    """
    import crcmod  # type: ignore

    crc32c_fun = crcmod.predefined.mkPredefinedCrcFun("crc-32c")
    return crc32c_fun(data)

Ruby

Per eseguire questo codice, prima configura un ambiente di sviluppo Ruby e installa l'SDK Ruby di Cloud KMS.

# TODO(developer): uncomment these values before running the sample.
# project_id  = "my-project"
# location_id = "us-east1"
# key_ring_id = "my-key-ring"
# key_id      = "my-key"
# version_id  = "123"
# ciphertext  = "..."

# Require the library.
require "google/cloud/kms"

# Create the client.
client = Google::Cloud::Kms.key_management_service

# Build the key version name.
key_version_name = client.crypto_key_version_path project:            project_id,
                                                  location:           location_id,
                                                  key_ring:           key_ring_id,
                                                  crypto_key:         key_id,
                                                  crypto_key_version: version_id

# Call the API.
response = client.asymmetric_decrypt key_version_name, ciphertext
puts "Plaintext: #{response.plaintext}"

API

Questi esempi utilizzano curl come client HTTP per dimostrare l'utilizzo dell'API. Per ulteriori informazioni sul controllo dell'accesso, vedi Accesso all'API Cloud KMS.

Utilizza la CryptoKeyVersions.asymmetricDecrypt .

Risoluzione dei problemi

incorrect key purpose: ASYMMETRIC_SIGN

Puoi decriptare i dati solo con una chiave con lo scopo della chiave ASYMMETRIC_DECRYPT.

invalid parameter durante la decrittografia su macOS

La versione di OpenSSL installata su macOS non supporta i flag utilizzati per decriptare i dati in questo argomento. Per seguire questi passaggi su macOS, installa OpenSSL da Homebrew.

data too large for key size

La dimensione massima del payload per la decrittografia RSA dipende dalla dimensione della chiave e dall'algoritmo di padding. Tutti i formati di crittografia RSA utilizzati da Cloud KMS utilizzano OAEP, standardizzato in RFC 2437. Come riferimento rapido, i seguenti algoritmi supportano il seguente dimensioni (maxMLen, in byte):

Algoritmo Parametri Lunghezza massima del messaggio
RSA_DECRYPT_OAEP_2048_SHA256 k = 256; hLen = 32; maxMLen = 190
RSA_DECRYPT_OAEP_3072_SHA256 k = 384; hLen = 32; maxMLen = 318
RSA_DECRYPT_OAEP_4096_SHA256 k = 512; hLen = 32; maxMLen = 446
RSA_DECRYPT_OAEP_4096_SHA512 k = 512; hLen = 64; maxMLen = 382

La crittografia asimmetrica non è consigliata per i messaggi di lunghezze diverse che possono essere superiori a questi limiti. Ti consigliamo di utilizzare la crittografia ibrida. Tink è una libreria crittografica che utilizza questo approccio.