接下来我们介绍对称加密算法，最常用的莫过于DES数据加密算法。
DES
DES-Data Encryption Standard,即数据加密算法。是IBM公司于1975年研究成功并公开发表的。DES算法的入口参数有三个:Key、Data、Mode。其中Key为8个字节共64位,是DES算法的工作密钥;Data也为8个字节64位,是要被加密或被解密的数据;Mode为DES的工作方式,有两种:加密或解密。
DES算法把64位的明文输入块变为64位的密文输出块,它所使用的密钥也是64位。
通过java代码实现如下：
Coder类见
Java加密技术（一）
Java代码
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;
public abstract class DESCoder
extends Coder {
public static final String ALGORITHM =
"DES";
private static Key toKey(
byte[] key)
throws Exception { DESKeySpec dks =
new DESKeySpec(key); SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM); SecretKey secretKey = keyFactory.generateSecret(dks);
return secretKey; }
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); }
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); }
public static String initKey()
throws Exception {
return initKey(
null); }
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()); } }
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安全编码组件
*
* <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
* 具体内容 需要关注 JDK Document http://.../docs/technotes/guides/security/SunProviders.html
* </pre>
*
* @author 梁栋
* @version 1.0
* @since 1.0
*/
public abstract class DESCoder extends Coder {
/**
* ALGORITHM 算法 <br>
* 可替换为以下任意一种算法，同时key值的size相应改变。
*
* <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)方法中使用下述代码
* <code>SecretKey secretKey = new SecretKeySpec(key, ALGORITHM);</code> 替换
* <code>
* DESKeySpec dks = new DESKeySpec(key);
* SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
* SecretKey secretKey = keyFactory.generateSecret(dks);
* </code>
*/
public static final String ALGORITHM = "DES";
/**
* 转换密钥<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);
// 当使用其他对称加密算法时，如AES、Blowfish等算法时，用下述代码替换上述三行代码
// 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);
}
/**
* 生成密钥
*
* @return
* @throws Exception
*/
public static String initKey() throws Exception {
return initKey(null);
}
/**
* 生成密钥
*
* @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());
}
}
延续上一个类的实现，我们通过MD5以及SHA对字符串加密生成密钥，这是比较常见的密钥生成方式。
再给出一个测试类：
Java代码
import static org.junit.Assert.*;
import org.junit.Test;
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(
"密钥:\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); } }
import static org.junit.Assert.*;
import org.junit.Test;
/**
*
* @author 梁栋
* @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("密钥:\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);
}
}
得到的输出内容如下：
Console代码
原文: DES 密钥: f3wEtRrV6q0= 加密后: C6qe9oNIzRY= 解密后: DES
原文: DES
密钥: f3wEtRrV6q0=
加密后: C6qe9oNIzRY=
解密后: DES
由控制台得到的输出，我们能够比对加密、解密后结果一致。这是一种简单的加密解密方式，只有一个密钥。
其实DES有很多同胞兄弟，如DESede(TripleDES)、AES、Blowfish、RC2、RC4(ARCFOUR)。这里就不过多阐述了，大同小异，只要换掉ALGORITHM换成对应的值，同时做一个代码替换
SecretKey secretKey = new SecretKeySpec(key, ALGORITHM);就可以了，此外就是密钥长度不同了。
Java代码
相关资源：敏捷开发V1.0.pptx
