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 程式師世界 >> 編程語言 >> JAVA編程 >> 關於JAVA >> Java加密技術(二)

Java加密技術(二)

編輯:關於JAVA

接下來我們介紹對稱加密算法,最常用的莫過於DES數據加密算法。

DES

DES-Data Encryption Standard,即數據加密算法。是IBM公司於1975年研究成功並公開發表的。DES算法的入口參數有三個:Key、Data、Mode。其中Key為8個字節共64位,是DES算法的工作密鑰;Data也為8個字節64位,是要被加密或被解密的數據;Mode為DES的工作方式,有兩種:加密或解密。

DES算法把64位的明文輸入塊變為64位的密文輸出塊,它所使用的密鑰也是64位。

通過java代碼實現如下:Coder類見 Java加密技術(一)

Java代碼

import java.security.Key;
import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

/**
  * DES安全編碼組件
  *
  * <pre>
  * 支持 DES、DESede(TripleDES,就是3DES)、AES、Blowfish、RC2、RC4(ARCFOUR)
  * DES
key size must be equal to 56
  * DESede(TripleDES)
key size must be equal to 112 or 168
  * AES
key size must be equal to 128, 192 or 256,but 192 and 256 bits may not be available
  * Blowfish
key size must be multiple of 8, and can only range from 32 to 448 (inclusive)
  * RC2
key size must be between 40 and 1024 bitS
  * RC4(ARCFOUR)
key size must be between 40 and 1024 bitS
  * 具體內容 需要關注 JDK Document http://.../docs/technotes/guides/security/SunProviders.html
  * </pre>
  *
  * @author 梁棟
  * @version 1.0
  * @since 1.0
  */
public abstract class DESCoder extends Coder {
/**
  * ALGORITHM 算法 <br>
  * 可替換為以下任意一種算法,同時key值的size相應改變。
  *
  * <pre>
  * DES
key size must be equal to 56
  * DESede(TripleDES)
key size must be equal to 112 or 168
  * AES
key size must be equal to 128, 192 or 256,but 192 and 256 bits may not be available
  * Blowfish
key size must be multiple of 8, and can only range from 32 to 448 (inclusive)
  * RC2
key size must be between 40 and 1024 bitS
  * RC4(ARCFOUR)
key size must be between 40 and 1024 bitS
  * </pre>
  *
  * 在Key toKey(byte[] key)方法中使用下述代碼
  * <code>SecretKey secretKey = new SecretKeySpec(key, ALGORITHM);</code> 替換
  * <code>
  * DESKeySpec dks = new DESKeySpec(key);
  * SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
  * SecretKey secretKey = keyFactory.generateSecret(dks);
  * </code>
  */
public static final String ALGORITHM = "DES";

/**
  * 轉換密鑰<br>
  *
  * @param key
  * @return
  * @throws Exception
  */
private static Key toKey(byte[] key) throws Exception {
DESKeySpec dks = new DESKeySpec(key);
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
SecretKey secretKey = keyFactory.generateSecret(dks);

// 當使用其他對稱加密算法時,如AES、Blowfish等算法時,用下述代碼替換上述三行代碼
// SecretKey secretKey = new SecretKeySpec(key, ALGORITHM);

return secretKey;
}

/**
  * 解密
  *
  * @param data
  * @param key
  * @return
  * @throws Exception
  */
public static byte[] decrypt(byte[] data, String key) throws Exception {
Key k = toKey(decryptBASE64(key));

Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, k);

return cipher.doFinal(data);
}

/**
  * 加密
  *
  * @param data
  * @param key
  * @return
  * @throws Exception
  */
public static byte[] encrypt(byte[] data, String key) throws Exception {
Key k = toKey(decryptBASE64(key));
Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, k);

return cipher.doFinal(data);
}

/**
  * 生成密鑰
  *
  * @return
  * @throws Exception
  */
public static String initKey() throws Exception {
return initKey(null);
}

/**
  * 生成密鑰
  *
  * @param seed
  * @return
  * @throws Exception
  */
public static String initKey(String seed) throws Exception {
SecureRandom secureRandom = null;

if (seed != null) {

secureRandom = new SecureRandom(decryptBASE64(seed));
} else {

secureRandom = new SecureRandom();
}

KeyGenerator kg = KeyGenerator.getInstance(ALGORITHM);
kg.init(secureRandom);

SecretKey secretKey = kg.generateKey();

return encryptBASE64(secretKey.getEncoded());
}
}

延續上一個類的實現,我們通過MD5以及SHA對字符串加密生成密鑰,這是比較常見的密鑰生成方式。

再給出一個測試類:

Java代碼

import static org.junit.Assert.*;
import org.junit.Test;
/** *//**
 *
 * @author by http://www.bt285.cn http://www.5a520.cn
 * @version 1.0
 * @since 1.0
 */
public class DESCoderTest {
    @Test
    public void test() throws Exception {
        String inputStr = "DES";
        String key = DESCoder.initKey();
        System.err.println("原文:\t" + inputStr);
        System.err.println("密鑰:\t" + key);
        byte[] inputData = inputStr.getBytes();
        inputData = DESCoder.encrypt(inputData, key);
        System.err.println("加密後:\t" + DESCoder.encryptBASE64(inputData));
        byte[] outputData = DESCoder.decrypt(inputData, key);
        String outputStr = new String(outputData);
        System.err.println("解密後:\t" + outputStr);
        assertEquals(inputStr, outputStr);
    }
}

得到的輸出內容如下:

Console代碼

原文:
DES
密鑰:
f3wEtRrV6q0=
加密後:
C6qe9oNIzRY=
解密後:
DES

由控制台得到的輸出,我們能夠比對加密、解密後結果一致。這是一種簡單的加密解密方式,只有一個密鑰。

其實DES有很多同胞兄弟,如DESede(TripleDES)、AES、Blowfish、RC2、RC4(ARCFOUR)。這裡就不過多闡述了,大同小異,只要換掉ALGORITHM換成對應的值,同時做一個代碼替換SecretKey secretKey = new SecretKeySpec(key, ALGORITHM);就可以了,此外就是密鑰長度不同了。

Java代碼

/**
  * DES     key size must be equal to 56
  * DESede(TripleDES) key size must be equal to 112 or 168
  * AES     key size must be equal to 128, 192 or 256,but 192 and 256 bits may not be available
  * Blowfish   key size must be multiple of 8, and can only range from 32 to 448 (inclusive)
  * RC2     key size must be between 40 and 1024 bitS
  * RC4(ARCFOUR) key size must be between 40 and 1024 bitS
  **/

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