使用Java进行加密和解密：无法获得相同的输出 [英] Encrypting and Decrypting Using Java: Unable to get same output

问题描述

我正在尝试学习和测试java 1.6加密/解密API。我想知道我做错了什么，我在知识方面缺少什么。

在下面的代码中，我创建了两个密码：一个用于加密，另一个用于解密。当我使用这些密码时，我使用不同的SecretKey来初始化它们，但是我仍然可以获得相同的值。为什么是这样？

  String algorithm =DES; 
 SecretKeyFactory keyFactory = SecretKeyFactory.getInstance（algorithm）; 
 
 byte [] encBytes =12345678.getBytes（UTF8）; 
 byte [] decBytes =56781234.getBytes（UTF8）; 
 
 DESKeySpec keySpecEncrypt = new DESKeySpec（encBytes）; 
 DESKeySpec keySpecDecrypt = new DESKeySpec（decBytes）; 
 
 
 SecretKey keyEncrypt = keyFactory.generateSecret（keySpecEncrypt）; 
 SecretKey keyDecrypt = keyFactory.generateSecret（keySpecDecrypt）; 
 
密码cipherEncrypt = Cipher.getInstance（algorithm）; 
密码cipherDecrypt = Cipher.getInstance（algorithm）; 
 
 String input =john doe; 
 
 cipherEncrypt.init（Cipher.ENCRYPT_MODE，keyEncrypt）; 
 byte [] inputBytes = cipherEncrypt.doFinal（input.getBytes（））; 
 System.out.println（inputBytes：+ new String（inputBytes））; 
 
 cipherDecrypt.init（Cipher.DECRYPT_MODE，keyDecrypt）; 
 byte [] outputBytes = cipherDecrypt.doFinal（inputBytes）; 
 System.out.println（outputBytes：+ new String（outputBytes））; 
  

解决方案

以下是JDK doc的描述：

 
 DESKeySpec 
 public DESKeySpec（byte [] key）
 throws InvalidKeyException 
使用前8个字节创建一个DESKeySpec对象作为DES密钥的关键材料。 
构成DES密钥的字节是密钥[0]和密钥[7]之间的字节。 
 

DESKeySpec仅使用byte []的前8个字节作为关键字。因此，使用的实际键在您的示例中是相同的。

I am trying to learn and test the java 1.6 encryption/decryption API. I want to know what I am doing wrong and what I am missing in terms of knowledge.

In the code that follows below, I create two ciphers: one to encrypt and another to decrypt. When I use these ciphers, I initialize them with different SecretKey's, but I am still able to get the same value back out. Why is this?

    String algorithm = "DES";
    SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(algorithm);

    byte[] encBytes = "12345678".getBytes("UTF8");
    byte[] decBytes = "56781234".getBytes("UTF8");

    DESKeySpec keySpecEncrypt = new DESKeySpec(encBytes);
    DESKeySpec keySpecDecrypt = new DESKeySpec(decBytes);


    SecretKey keyEncrypt = keyFactory.generateSecret(keySpecEncrypt);
    SecretKey keyDecrypt = keyFactory.generateSecret(keySpecDecrypt);

    Cipher cipherEncrypt = Cipher.getInstance(algorithm);
    Cipher cipherDecrypt = Cipher.getInstance(algorithm);

    String input = "john doe";

    cipherEncrypt.init(Cipher.ENCRYPT_MODE, keyEncrypt);
    byte[] inputBytes = cipherEncrypt.doFinal(input.getBytes());
    System.out.println("inputBytes: " + new String(inputBytes));

    cipherDecrypt.init(Cipher.DECRYPT_MODE, keyDecrypt);
    byte[] outputBytes = cipherDecrypt.doFinal(inputBytes);
    System.out.println("outputBytes: " + new String(outputBytes));

解决方案

Here's the description from JDK doc:

DESKeySpec
public DESKeySpec(byte[] key)
           throws InvalidKeyException
Creates a DESKeySpec object using the first 8 bytes in key as the key material for the DES key. 
The bytes that constitute the DES key are those between key[0] and key[7] inclusive. 

DESKeySpec uses only the first 8 bytes of byte[] as key. Thus the actual keys in used are identical in your example.

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