将字节数组转换为字符串再转换回字节数组的问题 [英] Problems converting byte array to string and back to byte array
问题描述
这个话题有很多问题，同样的解决方案，但这对我不起作用.我有一个简单的加密测试.加密/解密本身有效(只要我用字节数组本身而不是字符串来处理这个测试).问题是不想将其作为字节数组处理，而是作为字符串处理，但是当我将字节数组编码为字符串并返回时，生成的字节数组与原始字节数组不同，因此解密不再起作用.我在相应的字符串方法中尝试了以下参数:UTF-8、UTF8、UTF-16、UTF8.他们都没有工作.生成的字节数组与原始字节数组不同.任何想法为什么会这样?
There are a lot of questions with this topic, the same solution, but this doesn't work for me. I have a simple test with an encryption. The encryption/decryption itself works (as long as I handle this test with the byte array itself and not as Strings). The problem is that don't want to handle it as byte array but as String, but when I encode the byte array to string and back, the resulting byte array differs from the original byte array, so the decryption doesn't work anymore. I tried the following parameters in the corresponding string methods: UTF-8, UTF8, UTF-16, UTF8. None of them work. The resulting byte array differs from the original. Any ideas why this is so?
加密器:
public class NewEncrypter
{
private String algorithm = "DESede";
private Key key = null;
private Cipher cipher = null;
public NewEncrypter() throws NoSuchAlgorithmException, NoSuchPaddingException
{
key = KeyGenerator.getInstance(algorithm).generateKey();
cipher = Cipher.getInstance(algorithm);
}
public byte[] encrypt(String input) throws Exception
{
cipher.init(Cipher.ENCRYPT_MODE, key);
byte[] inputBytes = input.getBytes("UTF-16");
return cipher.doFinal(inputBytes);
}
public String decrypt(byte[] encryptionBytes) throws Exception
{
cipher.init(Cipher.DECRYPT_MODE, key);
byte[] recoveredBytes = cipher.doFinal(encryptionBytes);
String recovered = new String(recoveredBytes, "UTF-16");
return recovered;
}
}
这是我尝试的测试:
public class NewEncrypterTest
{
@Test
public void canEncryptAndDecrypt() throws Exception
{
String toEncrypt = "FOOBAR";
NewEncrypter encrypter = new NewEncrypter();
byte[] encryptedByteArray = encrypter.encrypt(toEncrypt);
System.out.println("encryptedByteArray:" + encryptedByteArray);
String decoded = new String(encryptedByteArray, "UTF-16");
System.out.println("decoded:" + decoded);
byte[] encoded = decoded.getBytes("UTF-16");
System.out.println("encoded:" + encoded);
String decryptedText = encrypter.decrypt(encoded); //Exception here
System.out.println("decryptedText:" + decryptedText);
assertEquals(toEncrypt, decryptedText);
}
}
推荐答案
将加密数据存储在字符串中不是一个好主意，因为它们用于人类可读的文本，而不是任意二进制数据.对于二进制数据，最好使用 byte[].
It is not a good idea to store encrypted data in Strings because they are for human-readable text, not for arbitrary binary data. For binary data it's best to use byte[].
但是，如果您必须这样做，您应该使用在字节和字符之间具有一对一映射的编码，即每个字节序列可以映射到唯一的字符序列，然后返回.其中一种编码是ISO-8859-1，即:
However, if you must do it you should use an encoding that has a 1-to-1 mapping between bytes and characters, that is, where every byte sequence can be mapped to a unique sequence of characters, and back. One such encoding is ISO-8859-1, that is:
String decoded = new String(encryptedByteArray, "ISO-8859-1");
System.out.println("decoded:" + decoded);
byte[] encoded = decoded.getBytes("ISO-8859-1");
System.out.println("encoded:" + java.util.Arrays.toString(encoded));
String decryptedText = encrypter.decrypt(encoded);
其他不会丢失数据的常见编码是十六进制和base64，但遗憾的是您需要一个辅助库来处理它们.标准 API 没有为它们定义类.
Other common encodings that don't lose data are hexadecimal and base64, but sadly you need a helper library for them. The standard API doesn't define classes for them.
使用 UTF-16 时程序会失败，原因有两个:
With UTF-16 the program would fail for two reasons:
- String.getBytes("UTF-16") 向输出添加一个字节顺序标记字符以标识字节的顺序.您应该使用 UTF-16LE 或 UTF-16BE 以免发生这种情况.
- 并非所有字节序列都可以映射到 UTF-16 中的字符.首先，以 UTF-16 编码的文本必须具有偶数个字节.其次，UTF-16 有一种机制可以对 U+FFFF 以外的 unicode 字符进行编码.这意味着例如有 4 个字节的序列仅映射到一个 unicode 字符.为此，4 个字节的前 2 个字节不使用 UTF-16 编码任何字符.
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