<壹>. MD5加密算法：
消息摘要算法第五版(Message Digest Algorithm)，是壹種單向加密算法，只能加密、無法解密。然而MD5加密算法已經被中國山東大學王小雲教授成功破譯，但是在安全性要求不高的場景下，MD5加密算法仍然具有應用價值。
1. 創建md5對象：?<pre name="code" class="java">MessageDigest md5 = MessageDigest.getInstance("md5");
2. ?進行加密操作：?byte[] cipherData = md5.digest(plainText.getBytes());
3. ?將其中的每個字節轉成十六進制字符串：byte類型的數據最高位是符號位，通過和0xff進行與操作，轉換為int類型的正整數。?String toHexStr = Integer.toHexString(cipher & 0xff);
4. 如果該正數小於16(長度為1個字符)，前面拼接0占位：確保最後生成的是32位字符串。?builder.append(toHexStr.length() == 1 ? "0" + toHexStr : toHexStr);
5.?加密轉換之後的字符串為：c0bb4f54f1d8b14caf6fe1069e5f93ad? 6. 完整的MD5算法應用如下所示：?/**
* 功能簡述: 測試MD5單向加密.
* @throws Exception
*/
@Test
public void test01() throws Exception {
String plainText = "Hello , world !";
MessageDigest md5 = MessageDigest.getInstance("md5");
byte[] cipherData = md5.digest(plainText.getBytes());
StringBuilder builder = new StringBuilder();
for(byte cipher : cipherData) {
String toHexStr = Integer.toHexString(cipher & 0xff);
builder.append(toHexStr.length() == 1 ? "0" + toHexStr : toHexStr);
}
System.out.println(builder.toString());
//c0bb4f54f1d8b14caf6fe1069e5f93ad
}
<二>. 使用BASE64進行加密/解密：
使用BASE64算法通常用作對二進制數據進行加密，加密之後的數據不易被肉眼識別。嚴格來說，經過BASE64加密的數據其實沒有安全性可言，因為它的加密解密算法都是公開的，典型的防菜鳥不防程序猿的呀。?經過標準的BASE64算法加密後的數據，?通常包含/、+、=等特殊符號，不適合作為url參數傳遞，幸運的是Apache的Commons Codec模塊提供了對BASE64的進壹步封裝。? (參見最後壹部分的說明)
1.?使用BASE64加密：?BASE64Encoder encoder = new BASE64Encoder();
String cipherText = encoder.encode(plainText.getBytes());
2.?使用BASE64解密：?BASE64Decoder decoder = new BASE64Decoder();
plainText = new String(decoder.decodeBuffer(cipherText));
3. 完整代碼示例：?/**
* 功能簡述: 使用BASE64進行雙向加密/解密.
* @throws Exception
*/
@Test
public void test02() throws Exception {
BASE64Encoder encoder = new BASE64Encoder();
BASE64Decoder decoder = new BASE64Decoder();
String plainText = "Hello , world !";
String cipherText = encoder.encode(plainText.getBytes());
System.out.println("cipherText : " + cipherText);
//cipherText : SGVsbG8gLCB3b3JsZCAh
System.out.println("plainText : " +
new String(decoder.decodeBuffer(cipherText)));
//plainText : Hello , world !
}
<三>. 使用DES對稱加密/解密：
?數據加密標準算法(Data Encryption Standard)，和BASE64最明顯的區別就是有壹個工作密鑰，該密鑰既用於加密、也用於解密，並且要求密鑰是壹個長度至少大於8位的字符串。使用DES加密、解密的核心是確保工作密鑰的安全性。
1.?根據key生成密鑰：?DESKeySpec keySpec = new DESKeySpec(key.getBytes());
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("des");
SecretKey secretKey = keyFactory.generateSecret(keySpec);
2.?加密操作：?Cipher cipher = Cipher.getInstance("des");
cipher.init(Cipher.ENCRYPT_MODE, secretKey, new SecureRandom());
byte[] cipherData = cipher.doFinal(plainText.getBytes());
3.?為了便於觀察生成的加密數據，使用BASE64再次加密：?String cipherText = new BASE64Encoder().encode(cipherData);
?生成密文如下：PtRYi3sp7TOR69UrKEIicA==?
4.?解密操作：?cipher.init(Cipher.DECRYPT_MODE, secretKey, new SecureRandom());
byte[] plainData = cipher.doFinal(cipherData);
String plainText = new String(plainData);
5. 完整的代碼demo：?/**
* 功能簡述: 使用DES對稱加密/解密.
* @throws Exception
*/
@Test
public void test03() throws Exception {
String plainText = "Hello , world !";
String key = "12345678"; //要求key至少長度為8個字符
SecureRandom random = new SecureRandom();
DESKeySpec keySpec = new DESKeySpec(key.getBytes());
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("des");
SecretKey secretKey = keyFactory.generateSecret(keySpec);
Cipher cipher = Cipher.getInstance("des");
cipher.init(Cipher.ENCRYPT_MODE, secretKey, random);
byte[] cipherData = cipher.doFinal(plainText.getBytes());
System.out.println("cipherText : " + new BASE64Encoder().encode(cipherData));
//PtRYi3sp7TOR69UrKEIicA==
cipher.init(Cipher.DECRYPT_MODE, secretKey, random);
byte[] plainData = cipher.doFinal(cipherData);
System.out.println("plainText : " + new String(plainData));
//Hello , world !
}
<四>. 使用RSA非對稱加密/解密：
RSA算法是非對稱加密算法的典型代表，既能加密、又能解密。和對稱加密算法比如DES的明顯區別在於用於加密、解密的密鑰是不同的。使用RSA算法，只要密鑰足夠長(壹般要求1024bit)，加密的信息是不能被破解的。用戶通過/Upload/Images/2014081321/99A5FC9C0C628374.gif" alt="尷尬" title="尷尬" border="0">
/**
* 功能簡述: 使用RSA非對稱加密/解密.
* @throws Exception
*/
@Test
public void test04() throws Exception {
String plainText = "Hello , world !";
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("rsa");
keyPairGenerator.initialize(1024);
KeyPair keyPair = keyPairGenerator.generateKeyPair();
PublicKey publicKey = keyPair.getPublic();
PrivateKey privateKey = keyPair.getPrivate();
Cipher cipher = Cipher.getInstance("rsa");
SecureRandom random = new SecureRandom();
cipher.init(Cipher.ENCRYPT_MODE, privateKey, random);
byte[] cipherData = cipher.doFinal(plainText.getBytes());
System.out.println("cipherText : " + new BASE64Encoder().encode(cipherData));
//gDsJxZM98U2GzHUtUTyZ/Ir/NXqRWKUJkl6olrLYCZHY3RnlF3olkWPZ35Dwz9BMRqaTL3oPuyVq
//sehvHExxj9RyrWpIYnYLBSURB1KVUSLMsd/ONFOD0fnJoGtIk+T/+3yybVL8M+RI+HzbE/jdYa/+
//yQ+vHwHqXhuzZ/N8iNg=
cipher.init(Cipher.DECRYPT_MODE, publicKey, random);
byte[] plainData = cipher.doFinal(cipherData);
System.out.println("plainText : " + new String(plainData));
//Hello , world !
Signature signature = Signature.getInstance("MD5withRSA");
signature.initSign(privateKey);
signature.update(cipherData);
byte[] signData = signature.sign();
System.out.println("signature : " + new BASE64Encoder().encode(signData));
//ADfoeKQn6eEHgLF8ETMXan3TfFO03R5u+cQEWtAQ2lRblLZw1DpzTlJJt1RXjU451I84v3297LhR
//co64p6Sq3kVt84wnRsQw5mucZnY+jRZNdXpcbwh2qsh8287NM2hxWqp4OOCf/+vKKXZ3pbJMNT/4
///t9ewo+KYCWKOgvu5QQ=
signature.initVerify(publicKey);
signature.update(cipherData);
boolean status = signature.verify(signData);
System.out.println("status : " + status);
//true
}