java加密與解密之——對稱加密

對稱加密:

DES代碼示例:

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;

/**

* 對稱加密演算法 DES

*/

public class TestDES {

/**密鑰演算法**/

public static final String KEY_ALGORITHM = "DES";

/**加密/解密演算法 /工作模式/填充方式**/

public static final String CIPHER_ALGORITHM = "DES/ECB/PKCS5PADDING";

private static final char[] CH_HEX = {"0","1","2","3","4","5","6","7","8","9","A",

"B","C","D","E","F"};

/**

*生成密鑰

* @return

* @throws Exception

*/

public static byte[] initKey() throws Exception{

//實例化密鑰生成器

KeyGenerator kg = KeyGenerator.getInstance(KEY_ALGORITHM);

//初始化密鑰生成器

kg.init(56, new SecureRandom());

//生成密鑰

SecretKey secretKey = kg.generateKey();

//獲得密鑰的二進位編碼形式

return secretKey.getEncoded();

}

/**

* 轉換密鑰

* @param key

* @return

* @throws Exception

*/

public static Key toKey(byte[] key) throws Exception{

//實例化des密鑰材料

DESKeySpec keySpec = new DESKeySpec(key);

//實例化密鑰工廠

SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(KEY_ALGORITHM);

//生成秘密密鑰

SecretKey secretKey = keyFactory.generateSecret(keySpec);

return secretKey;

}

/**

* 加密

* @param data

* @param key

* @return

* @throws Exception

*/

public static byte[] encrypt(byte[] data,byte[] key) throws Exception{

//還原密鑰

Key k = toKey(key);

//實例化

Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);

//初始化，設置化加密模式

cipher.init(Cipher.ENCRYPT_MODE,k);

return cipher.doFinal(data);

}

public static byte[] decrypt(byte[] data,byte[] key) throws Exception{

//還原密鑰

Key k = toKey(key);

//實例化

Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);

//初始化，設置化加密模式

cipher.init(Cipher.DECRYPT_MODE,k);

return cipher.doFinal(data);

}

public static void main(String[] args) {

String str = "ceshides";

try {

//獲得密鑰

byte[] keys = initKey();

//加密

byte[] encrypes = encrypt(str.getBytes(),keys);

String result = byteArrayToHex(encrypes);

System.out.println("加密後結果為:"+result);

//解密

hexStringToBytes(result);

byte[] decrypts = decrypt(hexStringToBytes(result), keys);

System.out.println("解密結果為:"+new String(decrypts));

} catch (Exception e) {

e.printStackTrace();

}

}

/**

* 將位元組數組轉化為16進位字元串

* @param bytes

* @return

*/

private static String byteArrayToHex(byte[] bytes){

// 一個位元組佔8位，一個十六進位字元佔4位；十六進位字元數組的長度為位元組數組長度的兩倍

char[] chars = new char[bytes.length*2];

int index = 0;

for(byte b:bytes){

//取位元組的高4位

chars[index++] = CH_HEX[b>>>4 & 0xf];

//取位元組的低4位

chars[index++] = CH_HEX[b & 0xf];

}

return new String(chars).toUpperCase();

}

/**

* 16進位字元串轉換為位元組數組

* @param hexString

* @return

*/

public static byte[] hexStringToBytes(String hexString) {

if (hexString == null || hexString.equals("")) {

return null;

}

hexString = hexString.toUpperCase();

int length = hexString.length() / 2;

char[] hexChars = hexString.toCharArray();

byte[] d = new byte[length];

for (int i = 0; i < length; i++) {

int pos = i * 2;

d[i] = (byte) (charToByte(hexChars[pos]) << 4 | charToByte(hexChars[pos + 1]));

}

return d;

}

private static byte charToByte(char c) {

return (byte) "0123456789ABCDEF".indexOf(c);

}

}

測試結果為:

加密後結果為:4B9ADEDC61FD508F082A1965C8AEB669

解密結果為:ceshides

微公號：roc_shangcp

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