Android實現DES和3DES算法

本文實現的Android下的是DES和3DES算法，Java同樣也適用。

DES算法如下：

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

public class DESUtils {
private static byte[] parse(String str) {
byte[] b = new byte[str.length() / 2];
for (int i = 0, n = str.length(); i < n; i += 2) {
b[i / 2] = (byte) (Integer.parseInt(str.substring(i, i + 2), 16));
}
return b;
}

/**
* 加密
* @param src
* @param password
* @return
*/
public static byte[] enCode(byte[] src, String password) {
try {
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
SecretKey key = keyFactory.generateSecret(new DESKeySpec(parse(password)));// 密鑰
Cipher cipher = Cipher.getInstance("DES");
cipher.init(Cipher.ENCRYPT_MODE, key);
return cipher.doFinal(src);// 明文
} catch (Exception e) {
e.printStackTrace();
}
return null;

}

/**
* 解密
* @param src
* @param password
* @return
* @throws Exception
*/
public static byte[] deCode(byte[] src, String password) throws Exception {
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
SecretKey key = keyFactory.generateSecret(new DESKeySpec(parse(password)));// 密鑰
Cipher cipher = Cipher.getInstance("DES");
cipher.init(Cipher.DECRYPT_MODE, key);
return cipher.doFinal(src);// 密文
}
}

3DES算法是進行了3次DES算法。
E是代表加密，D代表解密，K1,K2,K3代表3個密鑰。加密解密都是用DES算法，一般來說密鑰需要3個或兩個密鑰，如果3個密鑰都相同，則變成了DES算法，如果對加密強度要求沒有那麼高，可以用兩個密鑰，對應的是K1和K3密鑰相同。
3DES加密過程：EK1(加密)-->DK2(解密)-->EK3(加密)
3DES解密過程：DK3(解密)-->EK2(加密)-->DK1(解密)

3DES算法如下：

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

public class DES3Utils {

private static final String Algorithm = "DESede"; //定義 加密算法,可用 DES,DESede,Blowfish

//keybyte為加密密鑰，長度為24字節
//src為被加密的數據緩沖區（源）
public static byte[] encryptMode(byte[] keybyte, byte[] src) {
try {
//生成密鑰
SecretKey deskey = new SecretKeySpec(keybyte, Algorithm);

//加密
Cipher c1 = Cipher.getInstance(Algorithm);
c1.init(Cipher.ENCRYPT_MODE, deskey);
return c1.doFinal(src);
} catch (java.security.NoSuchAlgorithmException e1) {
e1.printStackTrace();
} catch (javax.crypto.NoSuchPaddingException e2) {
e2.printStackTrace();
} catch (java.lang.Exception e3) {
e3.printStackTrace();
}
return null;
}

//keybyte為加密密鑰，長度為24字節
//src為加密後的緩沖區
public static byte[] decryptMode(byte[] keybyte, byte[] src) {
try {
//生成密鑰
SecretKey deskey = new SecretKeySpec(keybyte, Algorithm);

//解密
Cipher c1 = Cipher.getInstance(Algorithm);
c1.init(Cipher.DECRYPT_MODE, deskey);
return c1.doFinal(src);
} catch (java.security.NoSuchAlgorithmException e1) {
e1.printStackTrace();
} catch (javax.crypto.NoSuchPaddingException e2) {
e2.printStackTrace();
} catch (java.lang.Exception e3) {
e3.printStackTrace();
}
return null;
}

//轉換成十六進制字符串
public static String byte2hex(byte[] b) {
String hs="";
String stmp="";

for (int n=0;n<b.length;n++) {
stmp=(java.lang.Integer.toHexString(b[n] & 0XFF));
if (stmp.length()==1) hs=hs+"0"+stmp;
else hs=hs+stmp;
if (n<b.length-1) hs=hs+":";
}
return hs.toUpperCase();
}
}

調用

//DES
//DES加密
byte[] en = DESUtils.enCode(hexStringToBytes("3132333435363738"), "A1A2A3A4A5A6A7A8");
//DES解密
try {
byte[] dn = DESUtils.deCode(hexStringToBytes("B1C3D2A87DBDB68FA73FBBBCD6F083AC"), "A1A2A3A4A5A6A7A8");

} catch (Exception e) {
e.printStackTrace();
}

//3DES
//3DES加密
String key = "A1A2A3A4A5A6A7A8" //K1密鑰
+"B1B2B3B4B5B6B7B8" //K2密鑰
+"A1A2A3A4A5A6A7A8"; //K3密鑰
byte[] result = DES3Utils.encryptMode(hexStringToBytes(key), hexStringToBytes("3132333435363738"));

//3DES解密
byte[] dnresult = DES3Utils.decryptMode(hexStringToBytes(key), hexStringToBytes("B0920ED6520EAF752E22A1F49B243353"));

//***************************************************************************************
//實現String到byte的轉換
public static byte[] hexStringToBytes(String string) {
String hexString = string.replaceAll(" ", "").toUpperCase();

if (hexString.length() <= 0)
return null;

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;
}

DES的明文是3132333435363738，密鑰是A1A2A3A4A5A6A7A8，加密後得到B1C3D2A87DBDB68FA73FBBBCD6F083AC，這裡面前面16位是明文加密而來的，後面的A73FBBBCD6F083AC是由0808080808080808加密而來的。這8個08是算法自動填充上去的。3DES同樣會填充8個08上去再加密。B0920ED6520EAF752E22A1F49B243353後面的2E22A1F49B243353是由填充的0808080808080808加密而來。

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