对称加密算法概念
加密密钥和解密密钥相同,大部分算法加密揭秘过程互逆。
特点:算法公开、(相比非对称加密)计算量小、加密速度快、效率高。
弱点:双方都使用同样的密钥,安全性得不到保证。
常用对称加密算法
DES(Data Encryption Standard)
3DES(DES加强版,使用3次DES计算,Triple DES,DESede)
AES(Advanced Encryption Standard,3DES加强版)
JDK版DES/3DES/AES算法调用模板
1. 生成密钥
//KeyGenerator,密钥生成器
KeyGenerator keyGen = KeyGenerator.getInstance("DES");//算法:DES,DESede,AES
//初始化密钥生成器
keyGen.init(56); //各算法密钥长度不同,参见说明
//生成密钥
SecretKey secretKey = keyGen.generateKey();
//生产字节码数据
byte[] key = secretKey.getEncoded();
说明:
1.通过「KeyGenerator.getInstance(“DES”)」生成密钥,
2.参数为算法名称:分别对应DES、DESede(即3DES)、AES
3.每种算法密钥长度参数:DES(56),3DES(112,168),AES(192,256)
2.加/解密
//通过字节码数据key 恢复密钥
SecretKey secretKey = new SecretKeySpec(key, "DES");
//Cipher完成加密/解密工作
Cipher cipher = Cipher.getInstance("DES");
//根据密钥,对Cipher初始化,并选择加密还是解密
cipher.init(Cipher.ENCRYPT_MODE, secretKey);
byte[] result = cipher.doFinal(data);
1.加密或解密都通过cipher.init()设置,参数:ENCRYPT_MODE/DECRYPT_MODE
2.加密或解密都通过cipher.doFinal() 执行,获得byte[]类型结果。
代码示例
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
public class DESUtil {
/*
* 生成密钥
*/
public static byte[] initKey() throws Exception{
KeyGenerator keyGen = KeyGenerator.getInstance("DES");
keyGen.init(56);
SecretKey secretKey = keyGen.generateKey();
return secretKey.getEncoded();
}
/*
* DES 加密
*/
public static byte[] encrypt(byte[] data, byte[] key) throws Exception{
SecretKey secretKey = new SecretKeySpec(key, "DES");
Cipher cipher = Cipher.getInstance("DES");
cipher.init(Cipher.ENCRYPT_MODE, secretKey);
byte[] cipherBytes = cipher.doFinal(data);
return cipherBytes;
}
/*
* DES 解密
*/
public static byte[] decrypt(byte[] data, byte[] key) throws Exception{
SecretKey secretKey = new SecretKeySpec(key, "DES");
Cipher cipher = Cipher.getInstance("DES");
cipher.init(Cipher.DECRYPT_MODE, secretKey);
byte[] plainBytes = cipher.doFinal(data);
return plainBytes;
}
//Test
public static void main(String[] args) throws Exception {
byte[] desKey = DESUtil.initKey();
System.out.println("DES KEY : " + BytesToHex.fromBytesToHex(desKey));
byte[] desResult = DESUtil.encrypt(DATA.getBytes(), desKey);
System.out.println(DATA + ">>>DES 加密结果>>>" + BytesToHex.fromBytesToHex(desResult));
byte[] desPlain = DESUtil.decrypt(desResult, desKey);
System.out.println(DATA + ">>>DES 解密结果>>>" + new String(desPlain));
}
}