針對大多數公開金鑰加密用途,我們建議使用 Hybrid Encryption 原始類型,搭配 DHKEM_X25519_HKDF_SHA256、HKDF_SHA256、AES_256_GCM 金鑰類型。
公開金鑰加密會使用兩把金鑰 (公開金鑰和私密金鑰) 保護資料。公開金鑰用於加密,私密金鑰則用於解密。如果傳送者無法儲存密碼,且需要使用公開金鑰加密資料,這是個不錯的選擇。
以下範例可協助您開始使用混合式加密基本單元:
C++
// A command-line utility for testing Tink Hybrid Encryption. #include <iostream> #include <memory> #include <ostream> #include <string> #include "absl/flags/flag.h" #include "absl/flags/parse.h" #include "absl/log/absl_check.h" #include "absl/status/status.h" #include "absl/status/statusor.h" #include "absl/strings/string_view.h" #include "tink/config/global_registry.h" #include "util/util.h" #ifndef TINK_EXAMPLES_EXCLUDE_HPKE #include "tink/hybrid/hpke_config.h" #endif #include "tink/hybrid/hybrid_config.h" #include "tink/hybrid_decrypt.h" #include "tink/hybrid_encrypt.h" #include "tink/keyset_handle.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, "", "Input file name"); ABSL_FLAG(std::string, output_filename, "", "Output file name"); ABSL_FLAG(std::string, context_info, "", "Context info for Hybrid Encryption/Decryption"); namespace { using ::crypto::tink::HybridDecrypt; using ::crypto::tink::HybridEncrypt; using ::crypto::tink::KeysetHandle; constexpr absl::string_view kEncrypt = "encrypt"; constexpr absl::string_view kDecrypt = "decrypt"; void ValidateParams() { // ... } } // namespace namespace tink_cc_examples { absl::Status HybridCli(absl::string_view mode, const std::string& keyset_filename, const std::string& input_filename, const std::string& output_filename, absl::string_view context_info) { absl::Status result = crypto::tink::HybridConfig::Register(); if (!result.ok()) return result; #ifndef TINK_EXAMPLES_EXCLUDE_HPKE // HPKE isn't supported when using OpenSSL as a backend. result = crypto::tink::RegisterHpke(); if (!result.ok()) return result; #endif // Read the keyset from file. absl::StatusOr<std::unique_ptr<KeysetHandle>> keyset_handle = ReadJsonCleartextKeyset(keyset_filename); if (!keyset_handle.ok()) return keyset_handle.status(); // Read the input. absl::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) { // Get the hybrid encryption primitive. absl::StatusOr<std::unique_ptr<HybridEncrypt>> hybrid_encrypt_primitive = (*keyset_handle) ->GetPrimitive<crypto::tink::HybridEncrypt>( crypto::tink::ConfigGlobalRegistry()); if (!hybrid_encrypt_primitive.ok()) { return hybrid_encrypt_primitive.status(); } // Generate the ciphertext. absl::StatusOr<std::string> encrypt_result = (*hybrid_encrypt_primitive)->Encrypt(*input_file_content, context_info); if (!encrypt_result.ok()) return encrypt_result.status(); output = encrypt_result.value(); } else { // operation == kDecrypt. // Get the hybrid decryption primitive. absl::StatusOr<std::unique_ptr<HybridDecrypt>> hybrid_decrypt_primitive = (*keyset_handle) ->GetPrimitive<crypto::tink::HybridDecrypt>( crypto::tink::ConfigGlobalRegistry()); if (!hybrid_decrypt_primitive.ok()) { return hybrid_decrypt_primitive.status(); } // Recover the plaintext. absl::StatusOr<std::string> decrypt_result = (*hybrid_decrypt_primitive)->Decrypt(*input_file_content, context_info); if (!decrypt_result.ok()) return decrypt_result.status(); output = decrypt_result.value(); } // Write the output to the output 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 context_info = absl::GetFlag(FLAGS_context_info); std::clog << "Using keyset from file " << keyset_filename << " to hybrid " << mode << " file " << input_filename << " with context info '" << context_info << "'." << '\n'; std::clog << "The resulting output will be written to " << output_filename << '\n'; ABSL_CHECK_OK(tink_cc_examples::HybridCli( mode, keyset_filename, input_filename, output_filename, context_info)); return 0; }
Go
import ( "bytes" "fmt" "log" "github.com/tink-crypto/tink-go/v2/hybrid" "github.com/tink-crypto/tink-go/v2/insecurecleartextkeyset" "github.com/tink-crypto/tink-go/v2/keyset" ) func Example() { // A private keyset created with // "tinkey create-keyset --key-template=DHKEM_X25519_HKDF_SHA256_HKDF_SHA256_AES_256_GCM --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.HpkePrivateKey", "value": "EioSBggBEAEYAhogVWQpmQoz74jcAp5WOD36KiBQ71MVCpn2iWfOzWLtKV4aINfn8qlMbyijNJcCzrafjsgJ493ZZGN256KTfKw0WN+p" }, "keyId": 958452012, "outputPrefixType": "TINK", "status": "ENABLED" }], "primaryKeyId": 958452012 }` // 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.HpkePublicKey", "value": "EgYIARABGAIaIFVkKZkKM++I3AKeVjg9+iogUO9TFQqZ9olnzs1i7Sle" }, "keyId": 958452012, "outputPrefixType": "TINK", "status": "ENABLED" }], "primaryKeyId": 958452012 }` // 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 HybridEncrypt primitive from publicKeysetHandle. encPrimitive, err := hybrid.NewHybridEncrypt(publicKeysetHandle) if err != nil { log.Fatal(err) } plaintext := []byte("message") encryptionContext := []byte("encryption context") ciphertext, err := encPrimitive.Encrypt(plaintext, encryptionContext) if err != nil { log.Fatal(err) } // 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 HybridDecrypt primitive from privateKeysetHandle. decPrimitive, err := hybrid.NewHybridDecrypt(privateKeysetHandle) if err != nil { log.Fatal(err) } decrypted, err := decPrimitive.Decrypt(ciphertext, encryptionContext) if err != nil { log.Fatal(err) } fmt.Println(string(decrypted)) // Output: message }
Java
package hybrid; import static java.nio.charset.StandardCharsets.UTF_8; import com.google.crypto.tink.HybridDecrypt; import com.google.crypto.tink.HybridEncrypt; import com.google.crypto.tink.InsecureSecretKeyAccess; import com.google.crypto.tink.KeysetHandle; import com.google.crypto.tink.RegistryConfiguration; import com.google.crypto.tink.TinkJsonProtoKeysetFormat; import com.google.crypto.tink.hybrid.HybridConfig; import java.nio.file.Files; import java.nio.file.Path; import java.nio.file.Paths; /** * A command-line utility for hybrid encryption. * * <p>It loads cleartext keys from disk - this is not recommended! * * <p>It requires the following arguments: * * <ul> * <li>mode: either 'encrypt' or 'decrypt'. * <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] contex-info: Bind the encryption to this context info. */ public final class HybridExample { 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 HybridExample encrypt/decrypt key-file input-file output-file context-info"); System.exit(1); } String mode = args[0]; if (!mode.equals("encrypt") && !mode.equals("decrypt")) { System.err.println("Incorrect mode. Please select encrypt or decrypt."); System.exit(1); } Path keyFile = Paths.get(args[1]); Path inputFile = Paths.get(args[2]); byte[] input = Files.readAllBytes(inputFile); Path outputFile = Paths.get(args[3]); byte[] contextInfo = new byte[0]; if (args.length == 5) { contextInfo = args[4].getBytes(UTF_8); } // Register all hybrid encryption key types with the Tink runtime. HybridConfig.register(); // Read the keyset into a KeysetHandle. KeysetHandle handle = TinkJsonProtoKeysetFormat.parseKeyset( new String(Files.readAllBytes(keyFile), UTF_8), InsecureSecretKeyAccess.get()); if (mode.equals("encrypt")) { // Get the primitive. HybridEncrypt encryptor = handle.getPrimitive(RegistryConfiguration.get(), HybridEncrypt.class); // Use the primitive to encrypt data. byte[] ciphertext = encryptor.encrypt(input, contextInfo); Files.write(outputFile, ciphertext); } else { HybridDecrypt decryptor = handle.getPrimitive(RegistryConfiguration.get(), HybridDecrypt.class); // Use the primitive to decrypt data. byte[] plaintext = decryptor.decrypt(input, contextInfo); Files.write(outputFile, plaintext); } } private HybridExample() {} }
Obj-C
Python
import tink from tink import hybrid from tink import secret_key_access def example(): """Encrypt and decrypt using hybrid encryption.""" # Register the hybrid encryption key managers. This is needed to create # HybridEncrypt and HybridDecrypt primitives later. hybrid.register() # A private keyset created with # tinkey create-keyset \ # --key-template=DHKEM_X25519_HKDF_SHA256_HKDF_SHA256_AES_256_GCM \ # --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.HpkePrivateKey", "value": "EioSBggBEAEYAhogVWQpmQoz74jcAp5WOD36KiBQ71MVCpn2iWfOzWLtKV4aINfn8qlMbyijNJcCzrafjsgJ493ZZGN256KTfKw0WN+p" }, "keyId": 958452012, "outputPrefixType": "TINK", "status": "ENABLED" }], "primaryKeyId": 958452012 }""" # 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.HpkePublicKey", "value": "EgYIARABGAIaIFVkKZkKM++I3AKeVjg9+iogUO9TFQqZ9olnzs1i7Sle" }, "keyId": 958452012, "outputPrefixType": "TINK", "status": "ENABLED" }], "primaryKeyId": 958452012 }""" # 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 HybridEncrypt primitive from the keyset handle. enc_primitive = public_keyset_handle.primitive(hybrid.HybridEncrypt) # Use enc_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 = enc_primitive.encrypt(b'message', b'context_info') # Create a keyset handle from the private keyset. 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 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 HybridDecrypt primitive from the private keyset handle. dec_primitive = private_keyset_handle.primitive(hybrid.HybridDecrypt) # Use dec_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. decrypted = dec_primitive.decrypt(ciphertext, b'context_info')
混合式加密
混合式加密基本體結合了對稱式加密的效率,以及公開金鑰 (非對稱式) 密碼編譯的便利性。任何人都可以使用公開金鑰加密資料,但只有擁有私密金鑰的使用者才能解密。
如果是混合式加密,寄件者會產生新的對稱金鑰,加密每則訊息的明文,產生密文。該對稱金鑰會使用接收者的公開金鑰封裝。在混合式解密中,接收者會解封對稱金鑰,然後使用該金鑰解密密文,還原原始明文。如要瞭解如何儲存或傳輸密文和金鑰封裝,請參閱 Tink Hybrid Encryption 線路格式。
混合式加密具有下列屬性:
- Secrecy:除非擁有私密金鑰,否則任何人都無法取得加密純文字的任何資訊 (長度除外)。
- 非對稱性:您可以使用公開金鑰加密密文,但解密時需要私密金鑰。
- 隨機化:加密方式為隨機。即使是相同明文,加密後也不會產生相同密文。這樣一來,攻擊者就無法得知特定明文對應的密文。
在 Tink 中,混合式加密會以一對基元表示:
- 使用 HybridEncrypt 進行加密
- 使用 HybridDecrypt 解密
內容資訊參數
除了明文之外,混合式加密還會接受額外參數 context_info,這個參數通常是來自環境的隱含公開資料,但應繫結至產生的密文。也就是說,密文可讓您確認內容資訊的完整性,但無法保證其機密性或真實性。實際內容資訊可以是空白或空值,但為確保正確解密產生的密文,解密時必須提供相同內容資訊值。
混合式加密的具體實作方式可以透過各種方式將情境資訊繫結至密文,例如:
- 將
context_info做為 AEAD 對稱式加密的關聯資料輸入內容 (請參閱 RFC 5116)。 - 將
context_info做為 HKDF 的「CtxInfo」輸入 (如果實作項目使用 HKDF 做為金鑰衍生函式,請參閱 RFC 5869)。
選擇車鑰類型
我們建議在多數情況下使用 DHKEM_X25519_HKDF_SHA256_HKDF_SHA256_AES_256_GCM
金鑰類型。這類金鑰會實作 RFC 9180 中指定的混合公開金鑰加密 (HPKE) 標準。HPKE 包含金鑰封裝機制 (KEM)、金鑰衍生函式 (KDF),以及具備相關聯資料的已驗證加密 (AEAD) 演算法。
DHKEM_X25519_HKDF_SHA256_HKDF_SHA256_AES_256_GCM具體採用以下做法:
- KEM:透過 Curve25519 執行 Diffie-Hellman,並使用 HKDF-SHA-256 推導共用密碼。
- KDF:HKDF-SHA-256,用於衍生傳送者和接收者環境。
- AEAD:AES-256-GCM,並根據 HPKE 標準產生 12 位元組的隨機數。
其他支援的 HPKE 金鑰類型包括但不限於:
DHKEM_X25519_HKDF_SHA256_HKDF_SHA256_AES_128_GCMDHKEM_X25519_HKDF_SHA256_HKDF_SHA256_CHACHA20_POLY1305DHKEM_P256_HKDF_SHA256_HKDF_SHA256_AES_128_GCMDHKEM_P521_HKDF_SHA512_HKDF_SHA512_AES_256_GCM
如要進一步瞭解 KEM、KDF 和 AEAD 的演算法選擇,請參閱 RFC 9180。
雖然我們不再建議使用,但 Tink 也支援 ECIES 的某些變體,如 Victor Shoup 的 ISO 18033-2 標準所述。以下列出部分支援的 ECIES 金鑰類型:
ECIES_P256_HKDF_HMAC_SHA256_AES128_GCMECIES_P256_COMPRESSED_HKDF_HMAC_SHA256_AES128_GCMECIES_P256_HKDF_HMAC_SHA256_AES128_CTR_HMAC_SHA256ECIES_P256_COMPRESSED_HKDF_HMAC_SHA256_AES128_CTR_HMAC_SHA256
最少屬性
- 純文字和背景資訊的長度不限 (範圍為 0..232 個位元組)
- 防範自適應選擇密文攻擊
- 以橢圓曲線為基礎的配置採用 128 位元安全性