如何在Java中使用AES算法解密加密的字符串？

Question

我無法用Java解密AES加密的文本。 這是我的代碼：

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.xml.bind.DatatypeConverter;

public class aesencrypt {

    public static void main(String[] args) throws Exception {
        String plainText = "Hello World";
        System.out.println("Original Text:" + plainText);
        SecretKey secKey = getSecretEncryptionKey();
        System.out.println("AES Key (Hex Form):"+bytesToHex(secKey.getEncoded()));
        String encryptedText = bytesToHex(encryptText(plainText, secKey));
        System.out.println("Encrypted Text (Hex Form):"+encryptedText);
        String decryptedText = decryptText(encryptedText, secKey);
        System.out.println("Descrypted Text:"+decryptedText);
    }

    public static SecretKey getSecretEncryptionKey() throws Exception{
        KeyGenerator generator = KeyGenerator.getInstance("AES");
        generator.init(128); // The AES key size in number of bits
        SecretKey secKey = generator.generateKey();
        return secKey;
    }

    public static byte[] encryptText(String plainText,SecretKey secKey) throws Exception{
        // AES defaults to AES/ECB/PKCS5Padding in Java 7
        Cipher aesCipher = Cipher.getInstance("AES");
        aesCipher.init(Cipher.ENCRYPT_MODE, secKey);
        byte[] byteCipherText = aesCipher.doFinal(plainText.getBytes());
        return byteCipherText;
    }

    public static String decryptText(String encrypted, SecretKey secKey) throws Exception {
        // AES defaults to AES/ECB/PKCS5Padding in Java 7
        Cipher aesCipher = Cipher.getInstance("AES");
        aesCipher.init(Cipher.DECRYPT_MODE, secKey);
        byte[] bytePlainText = aesCipher.doFinal(encrypted.getBytes());
        return new String(bytePlainText);
    }

    private static String bytesToHex(byte[] hash) {
        return DatatypeConverter.printHexBinary(hash);
    }

}

運行此命令時，在以下輸出中出現錯誤：

Original Text:Hello World
AES Key (Hex Form):4690FFCDC7B5E8B128F5BF45F0920527
Encrypted Text (Hex Form):7C092F40D592F9DF83F3D4E976612928
Exception in thread "main" javax.crypto.BadPaddingException: Given final block not properly padded
    at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:989)
    at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:845)
    at com.sun.crypto.provider.AESCipher.engineDoFinal(AESCipher.java:446)
    at javax.crypto.Cipher.doFinal(Cipher.java:2165)
    at aesencrypt.decryptText(aesencrypt.java:38)
    at aesencrypt.main(aesencrypt.java:15)

我已經搜索了Stack Overflow和搜索引擎，但實際上找不到解決方案。

問題解決了

更新 ：已解決問題，感謝JB Nizet提供了解決方案！

修改后的代碼：

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.xml.bind.DatatypeConverter;

public class aesencrypt {

    public static void main(String[] args) throws Exception {
        String plainText = "Hello World";
        System.out.println("Original Text:" + plainText);
        SecretKey secKey = getSecretEncryptionKey();
        System.out.println("AES Key (Hex Form):"+bytesToHex(secKey.getEncoded()));
        String encryptedText = bytesToHex(encryptText(plainText, secKey));
        System.out.println("Encrypted Text (Hex Form):"+encryptedText);
        String decryptedText = decryptText(encryptedText, secKey);
        System.out.println("Decrypted Text:"+decryptedText);
    }

    public static SecretKey getSecretEncryptionKey() throws Exception{
        KeyGenerator generator = KeyGenerator.getInstance("AES");
        generator.init(128);
        SecretKey secKey = generator.generateKey();
        return secKey;
    }

    public static byte[] encryptText(String plainText,SecretKey secKey) throws Exception{
        Cipher aesCipher = Cipher.getInstance("AES");
        aesCipher.init(Cipher.ENCRYPT_MODE, secKey);
        byte[] byteCipherText = aesCipher.doFinal(plainText.getBytes());
        return byteCipherText;
    }

    public static String decryptText(String encrypted, SecretKey secKey) throws Exception {
        Cipher aesCipher = Cipher.getInstance("AES");
        aesCipher.init(Cipher.DECRYPT_MODE, secKey);
        byte[] bytePlainText = aesCipher.doFinal(hexToByte(encrypted));
        return new String(bytePlainText);
    }

    private static String bytesToHex(byte[] hash) {
        return DatatypeConverter.printHexBinary(hash);
    }

    private static byte[] hexToByte(String txt) {
        return DatatypeConverter.parseHexBinary(txt);
    }

}

這是輸出：

Original Text:Hello World
AES Key (Hex Form):84526F32BEDDBEA5BFBCDE241AD9BBA2
Encrypted Text (Hex Form):25378032E5F52575B7CEF311D45F00BD
Decrypted Text:Hello World

Answer 1

看你在做什么：

String encryptedText = bytesToHex(encryptText(plainText, secKey));

在這里，您將純文本轉換為字節（使用有損，與平台有關的getBytes() ，順便說一句。您應該使用UTF8）。

然后，您將這些字節加密並得到一個字節數組。 然后，您將此字節數組編碼為十六進制。

因此，相反的操作將是：從十六進制解碼為字節，然后解密那些字節，然后從解密后的字節構造一個字符串。

但是，這是您正在做的事情：

String decryptedText = decryptText(encryptedText, secKey);

其中deleteText（）的作用是：

byte[] bytePlainText = aesCipher.doFinal(encrypted.getBytes());

因此，您永遠不會使用十六進制解碼。 如果你使用bytesToHex()在一邊，你需要使用hexToBytes()的另一邊。