java - 无法提取 Android KeyStore 私有(private)指数

Question

我想在 Android Keystore 中生成一个 RSA key 对。由于 Android 4.3 应该可以在 Android 系统 Keystore 中生成 RSA key 。

我通过(工作正常)生成我的 RSA key

        Calendar notBefore = Calendar.getInstance();
        Calendar notAfter = Calendar.getInstance();
        notAfter.add(1, Calendar.YEAR);
        KeyPairGeneratorSpec spec = new KeyPairGeneratorSpec.Builder(ctx)
                .setAlias("key")
                .setSubject(
                        new X500Principal(String.format("CN=%s, OU=%s",
                                "key", ctx.getPackageName())))
                .setSerialNumber(BigInteger.ONE)
                .setStartDate(notBefore.getTime())
                .setEndDate(notAfter.getTime()).build();
            KeyPairGenerator kpg;
            kpg = KeyPairGenerator.getInstance("RSA", "AndroidKeyStore");
            kpg.initialize(spec);
            KeyPair kp = kpg.genKeyPair();
            publicKey = kp.getPublic();
            privateKey = kp.getPrivate();

我的 RSA 加密看起来像(也有效):

    public static byte[] RSAEncrypt(final byte[] plain)
        throws NoSuchAlgorithmException, NoSuchPaddingException,
        InvalidKeyException, IllegalBlockSizeException, BadPaddingException {

    Cipher cipher = Cipher.getInstance("RSA");
    System.out.println("RSA Encryption key: " + publicKey.getAlgorithm());
    System.out.println("RSA Encryption key: " + publicKey.getEncoded());

    cipher.init(Cipher.ENCRYPT_MODE, publicKey);
    byte[] encryptedBytes = cipher.doFinal(plain);
    return encryptedBytes;
}

解密:

    public static byte[] RSADecrypt(final byte[] encryptedBytes)
        throws NoSuchAlgorithmException, NoSuchPaddingException,
        InvalidKeyException, IllegalBlockSizeException, BadPaddingException {

    Cipher cipher1 = Cipher.getInstance("RSA");

    System.out.println("RSA Encryption key: " + privateKey.getAlgorithm());
    System.out.println("RSA Encryption key: " + privateKey.getEncoded());

    cipher1.init(Cipher.DECRYPT_MODE, privateKey);
    byte[] decryptedBytes = cipher1.doFinal(encryptedBytes);
    return decryptedBytes;
}

在解密函数中，我收到以下错误消息(当对私钥进行编码时，在 cipher1.init() 中):

12-12 21:49:40.338: E/AndroidRuntime(20423): FATAL EXCEPTION: main
12-12 21:49:40.338: E/AndroidRuntime(20423): java.lang.UnsupportedOperationException: private    exponent cannot be extracted
12-12 21:49:40.338: E/AndroidRuntime(20423):    at org.apache.harmony.xnet.provider.jsse.OpenSSLRSAPrivateKey.getPrivateExponent(OpenSSLRSAPrivateKey.java:143)

我不明白。 Android KeyStore 中无法生成 RSA key 吗？谁能给我提供一个在 Android KeyStore 中生成 RSA key 并使用私钥解密的示例。

非常感谢!

Answer 1

根据 the code ，我认为当 key 生成到设备中时，OpenSSL 提供程序会阻止导出私有(private)指数。

@Override
public final BigInteger getPrivateExponent() {
    if (key.isEngineBased()) {
        throw new UnsupportedOperationException("private exponent cannot be extracted");
    }

    ensureReadParams();
    return privateExponent;
}

因此，您可能需要指定在检索密码实例时要使用相同的加密提供程序。本商supports these RSA ciphers :

• RSA/ECB/NoPadding
• RSA/ECB/PKCS1Padding

您应该以这种方式创建密码实例:

Cipher cipher1 = Cipher.getInstance("RSA/ECB/PKCS1Padding", "AndroidOpenSSL");