如何在Java中使用keystore来存储私钥？

Question

我曾经习惯KeyPairGenerator生成一个RSA密钥对.如果我没错,KeyStore仅用于存储证书而不是密钥.如何在计算机上正确存储私钥？

Answer 1

你可以这样做:

 KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
 kpg.initialize(2048);

 KeyPair kp = kpg.genKeyPair();

 KeyFactory fact = KeyFactory.getInstance("RSA");

 RSAPublicKeySpec pub = fact.getKeySpec(kp.getPublic(),
        RSAPublicKeySpec.class);
 saveToFile(PUBLIC_KEY_FILE, 
        pub.getModulus(), pub.getPublicExponent());

 RSAPrivateKeySpec priv = fact.getKeySpec(kp.getPrivate(),
        RSAPrivateKeySpec.class);
 saveToFile(PRIVATE_KEY_FILE, 
         priv.getModulus(), priv.getPrivateExponent());

保存功能:

private static void saveToFile(String fileName,
                               BigInteger mod, BigInteger exp) 
    throws SomeException {
    ObjectOutputStream oout = new ObjectOutputStream(
            new BufferedOutputStream(new FileOutputStream(fileName)));
    try {
        oout.writeObject(mod);
        oout.writeObject(exp);
    } catch (Exception e) {
        throw new SomeException(e);
    } finally {
        oout.close();
    }
}

并以同样的方式回读:

private static PublicKey readPublicKey() throws SomeException {
    InputStream in = new FileInputStream(PUBLIC_KEY_FILE);
    ObjectInputStream oin =
            new ObjectInputStream(new BufferedInputStream(in));
    try {
        BigInteger m = (BigInteger) oin.readObject();
        BigInteger e = (BigInteger) oin.readObject();
        RSAPublicKeySpec keySpec = new RSAPublicKeySpec(m, e);
        KeyFactory fact = KeyFactory.getInstance("RSA");
        PublicKey pubKey = fact.generatePublic(keySpec);
        return pubKey;
    } catch (Exception e) {
        throw new SomeException(e);
    } finally {
        oin.close();
    }
}

读私钥是类似的.

Answer 2

这段代码将在AndroidKeyStore上生成并存储KeyPair.(注意:省略了异常捕获)

KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
keyStore.load(null);

String alias = "my_key"; // replace as required or get it as a function argument

int nBefore = keyStore.size(); // debugging variable to help convince yourself this works

// Create the keys if necessary
if (!keyStore.containsAlias(alias)) {

    Calendar notBefore = Calendar.getInstance();
    Calendar notAfter = Calendar.getInstance();
    notAfter.add(Calendar.YEAR, 1);
    KeyPairGeneratorSpec spec = new KeyPairGeneratorSpec.Builder(this)
                    .setAlias(alias)
                    .setKeyType("RSA")
                    .setKeySize(2048)
                    .setSubject(new X500Principal("CN=test"))
                    .setSerialNumber(BigInteger.ONE)
                    .setStartDate(notBefore.getTime())
                    .setEndDate(notAfter.getTime())
                    .build();
    KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA", "AndroidKeyStore");
    generator.initialize(spec);

    KeyPair keyPair = generator.generateKeyPair();
}
int nAfter = keyStore.size();
Log.v(TAG, "Before = " + nBefore + " After = " + nAfter);

// Retrieve the keys
KeyStore.PrivateKeyEntry privateKeyEntry = (KeyStore.PrivateKeyEntry)keyStore.getEntry(alias, null);
RSAPrivateKey privateKey = (RSAPrivateKey) privateKeyEntry.getPrivateKey();
RSAPublicKey publicKey = (RSAPublicKey) privateKeyEntry.getCertificate().getPublicKey();

Log.v(TAG, "private key = " + privateKey.toString());
Log.v(TAG, "public key = " + publicKey.toString());