接下來我們介紹對稱加密算法，最常用的莫過于DES數據加密算法。
DES
DES-Data Encryption Standard，即數據加密算法。是IBM公司于1975年研究成功并公開發表的。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
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 author by http://www.bt285.cn http://www.5a520.cn
*
* <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：
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("加密后:\t" + DESCoder.encryptBASE64(inputData));
byte[] outputData = DESCoder.decrypt(inputData, key);
String outputStr = new String(outputData);
System.err.println("解密后:\t" + outputStr);
assertEquals(inputStr, outputStr);
}
} |
得到的輸出內容如下：
原文： DES
密鑰： f3wEtRrV6q0=
加密后： C6qe9oNIzRY=
解密后： DES
由控制臺得到的輸出，我們能夠比對加密、解密后結果一致。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）。這里就不過多闡述了，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。
/**
* 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
**/ |
posted on 2009-12-18 11:47
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