Java - 使用现有的公钥文件加密字符串 [英] Java - Encrypt String with existing public key file

问题描述

过去 4-5 小时我一直在研究这个问题，尽管找到了使用从几种方法到整个 ~100 行类.我无法想象没有一些简单的功能可以做这样一件微不足道的事情:P

I've been researching this for the past 4-5 hours now and can't seem to find an answer that actually works despite finding 'answers' that used everything from a few methods to an entire ~100 line class. I can't imagine that there isn't some simple function to do such a trivial thing :P

我有一组预先存在的公钥/私钥(实际上，两组 - 一组由 ssh-keygen 生成，另一组由 openssl 生成，所以......无论哪种格式都很好).

I have a pre-existing set of public / private keys (actually, two sets - one generated by ssh-keygen and another by openssl so .. whatever format works is cool).

我所追求的只是一个简单的 java，相当于我用 python 编写的东西 -

All I am after is a simple java equivalent to what I write in python like -

key_object = someModule.KeyObject(nameOfPublicKeyFile)

def encrypt (SomePlainText) :
  return someOtherModule.encrypt(key_object, SomePlainText)

任何帮助都会很棒！

推荐答案

shell 中的这些 openssl 命令创建一个 RSA 密钥对，并将公钥和私钥写入 DER 格式的文件.

These openssl commands in the shell create an RSA key pair and write the public and private keys to DER formatted files.

这里，为了简单起见，私钥文件不受密码保护 (-nocrypt).

$ openssl genrsa -out keypair.pem 2048
Generating RSA private key, 2048 bit long modulus
............+++
................................+++
e is 65537 (0x10001)
$ openssl rsa -in keypair.pem -outform DER -pubout -out public.der
writing RSA key
$ openssl pkcs8 -topk8 -nocrypt -in keypair.pem -outform DER -out private.der

现在您有了 DER 文件，您可以用 Java 读取它们并使用 KeySpec 和 KeyFactory 来创建 PublicKey 和 PrivateKey 对象.

Now that you have the DER files, you can read them in Java and use KeySpec and KeyFactory to create PublicKey and PrivateKey objects.

public byte[] readFileBytes(String filename) throws IOException
{
    Path path = Paths.get(filename);
    return Files.readAllBytes(path);        
}

public PublicKey readPublicKey(String filename) throws IOException, NoSuchAlgorithmException, InvalidKeySpecException
{
    X509EncodedKeySpec publicSpec = new X509EncodedKeySpec(readFileBytes(filename));
    KeyFactory keyFactory = KeyFactory.getInstance("RSA");
    return keyFactory.generatePublic(publicSpec);       
}

public PrivateKey readPrivateKey(String filename) throws IOException, NoSuchAlgorithmException, InvalidKeySpecException
{
    PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(readFileBytes(filename));
    KeyFactory keyFactory = KeyFactory.getInstance("RSA");
    return keyFactory.generatePrivate(keySpec);     
}

使用公钥和私钥，您可以加密和解密少量数据(适合您的 RSA 模数).我建议使用 OAEP 填充.

With the public and private keys, you can encrypt and decrypt small amounts of data (that fit within your RSA modulus.) I recommend OAEP padding.

public byte[] encrypt(PublicKey key, byte[] plaintext) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException
{
    Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPWithSHA1AndMGF1Padding");   
    cipher.init(Cipher.ENCRYPT_MODE, key);  
    return cipher.doFinal(plaintext);
}

public byte[] decrypt(PrivateKey key, byte[] ciphertext) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException
{
    Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPWithSHA1AndMGF1Padding");   
    cipher.init(Cipher.DECRYPT_MODE, key);  
    return cipher.doFinal(ciphertext);
}

这里是通过简单的加密和解密绑定在一起的:

Here it is tied together with a simple encryption and decryption:

public void Hello()
{
    try
    {
        PublicKey publicKey = readPublicKey("public.der");
        PrivateKey privateKey = readPrivateKey("private.der");
        byte[] message = "Hello World".getBytes("UTF8");
        byte[] secret = encrypt(publicKey, message);
        byte[] recovered_message = decrypt(privateKey, secret);
        System.out.println(new String(recovered_message, "UTF8"));
    }
    catch (Exception e)
    {
        e.printStackTrace();
    }
}

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