java密碼術中'AGCM256-KW'的算法字符串是什么，用於Cipher.getInstance（String算法）？

Question

參考這個 ，我必須使用算法AGCM256-KW加密。 我正在使用Java Cryptography，我沒有找到任何這樣的算法。 我發現最接近的是AES_256 / GCM / NoPadding，但它沒有KW（密鑰包裝）。

這是我的測試代碼

    public void testEncryption(String algo) {
    String shared_secret = "LyQnklSrxsk3Ch2+AHi9HoDW@//x1LwM123QP/ln";
    try {

        // Step 1 - Create SHA-256 digest of the shared key
        MessageDigest md = MessageDigest.getInstance("SHA-256");
        byte[] digest = md.digest(shared_secret.getBytes("UTF-8"));

        // Step 2 - generate a 256 bit Content Encryption Key(CEK)
        KeyGenerator kg = KeyGenerator.getInstance("AES");
        kg.init(256);
        SecretKey cek = kg.generateKey();

        // Step 3 - encrypt the CEK using 256 bit digest generated in Step 1
        // and 96 bit random IV. Algorithm should be

        // random 96 bit Initialize Vector
        SecureRandom random = new SecureRandom();
        // byte iv[] = new byte[96];
        // random.nextBytes(iv);
        byte iv[] = random.generateSeed(96);
        System.out.println("IV: " + toBase64(iv) + " length: " + iv.length);
        IvParameterSpec ivspec = new IvParameterSpec(iv);
        GCMParameterSpec gspec = new GCMParameterSpec(96, iv);

        // encrypt
        Cipher cipher = Cipher.getInstance(algo);
        System.out.println(String.format("CEK Cipher alg:%S provider:%S", cipher.getAlgorithm(),
                cipher.getProvider().getName()));

        cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(digest, "AES"), gspec);
        byte[] result = cipher.doFinal(cek.getEncoded());

        System.out.println(String.format("Encrypted CEK :%S", toBase64(result)));

    } catch (NoSuchAlgorithmException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (UnsupportedEncodingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (InvalidKeyException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (InvalidAlgorithmParameterException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (NoSuchPaddingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IllegalBlockSizeException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (BadPaddingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

更新1我想我可以使用jose4j庫，它有適用於JWE的 API。

Answer 1

是的，Visa令牌服務似乎使用JWE（現在是RFC 7516 ），因此您可以使用jose4j。 下面是一些示例代碼，顯示使用A256GCMKW和AGCM256使用JWE加密和解密某些內容：

    // shared secret hashed to key from your example
    String shared_secret = "LyQnklSrxsk3Ch2+AHi9HoDW@//x1LwM123QP/ln";
    MessageDigest md = MessageDigest.getInstance("SHA-256");
    byte[] digest = md.digest(shared_secret.getBytes("UTF-8"));

    JsonWebEncryption jwe = new JsonWebEncryption();

    // A256GCMKW for key wrap
    jwe.setAlgorithmHeaderValue(KeyManagementAlgorithmIdentifiers.A256GCMKW);

    // A256GCM for content encryption
    jwe.setEncryptionMethodHeaderParameter(ContentEncryptionAlgorithmIdentifiers.AES_256_GCM);

    // the key (from above)
    jwe.setKey(new SecretKeySpec(digest, "AES"));

    // whatever content you want to encrypt
    jwe.setPayload("some important content to be encrypted and integrity protected");

    // Produce the JWE compact serialization, which is where the actual encryption is done.
    // The JWE compact serialization consists of five base64url encoded parts
    // combined with a dot ('.') character in the general format of
    // <header>.<encrypted key>.<initialization vector>.<ciphertext>.<authentication tag>
    String serializedJwe = jwe.getCompactSerialization();


    // Do something with the JWE. Like send it to some other party over the clouds
    // and through the interwebs.
    System.out.println("JWE compact serialization: " + serializedJwe);

    // That other party, the receiver, can then use JsonWebEncryption to decrypt the message.
    JsonWebEncryption receiverJwe = new JsonWebEncryption();

    // Set the compact serialization on new Json Web Encryption object
    receiverJwe.setCompactSerialization(serializedJwe);

    // Symmetric encryption, like we are doing here, requires that both parties have the same key.
    // The key will have had to have been securely exchanged out-of-band somehow.
    receiverJwe.setKey(new SecretKeySpec(digest, "AES"));

    // Get the message that was encrypted in the JWE. This step performs the actual decryption steps.
    String plaintext = receiverJwe.getPlaintextString();

    // And do whatever you need to do with the clear text message.
    System.out.println("plaintext: " + plaintext);

Answer 2

假設您確實在GCM模式下確實需要AES（我從未聽說過AGCM，但我想這是一個邏輯假設，它意味着AES / GCM）。 然后，以下內容可用於（un）包裝密鑰。 請注意，我沒有使用IvParameterSpec ，至少不適用於Oracle JCE。

SecretKey sk = new SecretKeySpec(new byte[16], "AES");
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
GCMParameterSpec gcmSpec = new GCMParameterSpec(128, new byte[12]);
cipher.init(Cipher.WRAP_MODE, sk, gcmSpec);
byte[] wrappedKey = cipher.wrap(sk);
System.out.println(Hex.toHexString(wrappedKey));

cipher.init(Cipher.UNWRAP_MODE, sk, gcmSpec);
SecretKey unwrap = (SecretKey) cipher.unwrap(wrappedKey, "AES", Cipher.SECRET_KEY);
System.out.println(Hex.toHexString(unwrap.getEncoded()));

請注意，對於包裝密鑰，使用SIV模式可能有點優先，因為您不需要將IV 和身份驗證標記與包裝密鑰一起存儲（存儲IV未在示例中顯示）。 上面的代碼依賴於唯一的IV安全性（也未示出）。

顯然，用自己包裝一個密鑰也不是一個好主意。 對不起，我這里有點懶; 我剛剛展示了如何使用密碼。

Answer 3

“KW”指的是“密鑰包裝”，如RFC 3394中所定義.JCE中該算法的名稱是“AESWrap”。 因此，轉換應該是“AESWrap / GCM / NoPadding”。 正如Maarten指出的那樣，邏輯上這個操作應該在WRAP_MODE配置Cipher 。