使用Java实现RSA加密/解密

Question

我正在做一个简单的程序来加密/解密使用RSA算法在Java。我创建一个密码对象如下：

//Create a Cipher object
Cipher rsaCipher = Cipher.getInstance("RSA/ECB/NoPadding");

我通过调用加密函数进行加密：

String cipher=encrypt(textByte, pair, rsaCipher);
System.out.println("The Encryption using RSA Algorithm : "+cipher);

解密过程如下：

//Decryption
String plain=decrypt(Base64.decodeBase64(cipher),pair, rsaCipher);
System.out.println("The Decryption using RSA Algorithm : "+plain);

但是，当我将创建密码对象的代码编辑为：//Create a Cipher object Cipher rsapier=Cipher时。getInstance（“RSA”）；

问题出在哪里。在第一种情况下（当空格出现时），我指定了NoPadd？为什么空格出现在解密的消息中？即使我使用填充，我希望这不应该发生。

编辑：这是加密和解密方法：

public static String encrypt(byte[] textBytes, KeyPair pair, Cipher rsaCipher) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException
{
    //get the public key
    PublicKey pk=pair.getPublic(); 


    //Initialize the cipher for encryption. Use the public key.
    rsaCipher.init(Cipher.ENCRYPT_MODE, pk);

    //Perform the encryption using doFinal
    byte[] encByte = rsaCipher.doFinal(textBytes);

    // converts to base64 for easier display.
    byte[] base64Cipher = Base64.encodeBase64(encByte);

    return new String(base64Cipher);
}//end encrypt

public static String decrypt(byte[] cipherBytes, KeyPair pair, Cipher rsaCipher) throws IllegalBlockSizeException, BadPaddingException, InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException
{
    //get the public key
    PrivateKey pvk=pair.getPrivate(); 

    //Create a Cipher object
    //Cipher rsaCipher = Cipher.getInstance("RSA/ECB/NoPadding");

    //Initialize the cipher for encryption. Use the public key.
    rsaCipher.init(Cipher.DECRYPT_MODE, pvk);

    //Perform the encryption using doFinal
    byte[] decByte = rsaCipher.doFinal(cipherBytes);

    return new String(decByte);

}//end decrypt

Answer 1

//This is a complete encryption and decryption module using 
//Algorithm: JWEAlgorithm.RSA_OAEP_256
//Encryption Method: A128CBC_HS256

public static String  encrypt(String text) throws Exception {
    // Set the plain text
    Payload payload = new Payload(text);
    // Create the header
    JWEHeader header = new JWEHeader(JWEAlgorithm.RSA_OAEP_256, EncryptionMethod.A128CBC_HS256);
    // Create the JWE object and encrypt it
    JWEObject jweObject = new JWEObject(header, payload);
    jweObject.encrypt(new RSAEncrypter(getPublicKey()));
    // Serialise to compact JOSE form...
    String jweString = jweObject.serialize();
    LOG.info("Generated Encrypted Key : {}", jweString);
    return jweString;
}

public static String decrypt(String text) throws Exception {
    // Parse into JWE object...
    JWEObject jweObject = JWEObject.parse(text);
    jweObject.decrypt(new RSADecrypter(getPrivateKey()));
    // Get the plain text
    Payload payload = jweObject.getPayload();
    System.out.println(payload.toString());
    return payload.toString();
}

private static RSAPublicKey getPublicKey() throws Exception {
    String filename = "/home/vaibhav/Setups/cert/pub.der";
    File f = new File(filename);
    FileInputStream fis = new FileInputStream(f);
    DataInputStream dis = new DataInputStream(fis);
    byte[] keyBytes = new byte[(int)f.length()];
    dis.readFully(keyBytes);
    dis.close();

    X509EncodedKeySpec spec = new X509EncodedKeySpec(keyBytes);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    return (RSAPublicKey) kf.generatePublic(spec);
}

private static RSAPrivateKey getPrivateKey() throws Exception {
    String filename = "/home/vaibhav/Setups/cert/private.pkcs8";
    File f = new File(filename);
    FileInputStream fis = new FileInputStream(f);
    DataInputStream dis = new DataInputStream(fis);
    byte[] keyBytes = new byte[(int)f.length()];
    dis.readFully(keyBytes);
    dis.close();

    PKCS8EncodedKeySpec spec1 = new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    return (RSAPrivateKey) kf.generatePrivate(spec1);
}

Answer 2

你的问题确实是填充物。安全的RSA功能需要某种填充，PKCS#1.5或OAEP填充。再者，要求查找加密的纯文本的开始和结束。

RSA的模块化指数是使用大整数执行的。然后，这些操作的结果表示为八位组字符串。这些八位字符串基本上是整数的大端、无符号、固定长度表示。这些整数保留00值字节（在RSA标准中称为I2OS原语）。所以您看到的是模块化指数的结果，00填充仍然存在。

长话短说，始终使用填充方案。如今，OAEP更可取。与混合加密方案一起使用，或使用更高级别的容器格式，如CMS或PGP。