RSA加密解密
RSA
這種算法1978年就出現了，它是第一個既能用於數據加密也能用於數字簽名的算法。它易於理解和操作，也很流行。算法的名字以發明者的名字命名：Ron Rivest, AdiShamir 和Leonard Adleman。
這種加密算法的特點主要是密鑰的變化，上文我們看到DES只有一個密鑰。相當於只有一把鑰匙，如果這把鑰匙丟了，數據也就不安全了。RSA同時有兩把鑰匙，公鑰與私鑰。同時支持數字簽名。數字簽名的意義在於，對傳輸過來的數據進行校驗。確保數據在傳輸工程中不被修改。
流程分析：
- 甲方構建密鑰對兒，將公鑰公佈給乙方，將私鑰保留。
- 甲方使用私鑰加密數據，然後用私鑰對加密後的數據簽名，發送給乙方簽名以及加密後的數據；乙方使用公鑰、簽名來驗證待解密數據是否有效，如果有效使用公鑰對數據解密。
- 乙方使用公鑰加密數據，向甲方發送經過加密後的數據；甲方獲得加密數據，通過私鑰解密。
通過java代碼實現如下：
Coder類
public class Coder {
public static final String KEY_SHA = "SHA";
public static final String KEY_MD5 = "MD5";
/**
* BASE64解密
*
* @param key
* @return
* @throws Exception
*/
public static byte[] decryptBASE64(String key) throws Exception {
return (new BASE64Decoder()).decodeBuffer(key);
}
/**
* BASE64加密
*
* @param key
* @return
* @throws Exception
*/
public static String encryptBASE64(byte[] key) throws Exception {
return (new BASE64Encoder()).encodeBuffer(key);
}
/**
* MD5加密
*
* @param data
* @return
* @throws Exception
*/
public static byte[] encryptMD5(byte[] data) throws Exception {
MessageDigest md5 = MessageDigest.getInstance(KEY_MD5);
md5.update(data);
return md5.digest();
}
/**
* SHA加密
*
* @param data
* @return
* @throws Exception
*/
public static byte[] encryptSHA(byte[] data) throws Exception {
MessageDigest sha = MessageDigest.getInstance(KEY_SHA);
sha.update(data);
return sha.digest();
}
關鍵生成祕鑰私鑰類
public abstract class RSACoder extends Coder {
public static final String KEY_ALGORITHM = "RSA";
public static final String SIGNATURE_ALGORITHM = "MD5withRSA";
private static final String PUBLIC_KEY = "RSAPublicKey";
private static final String PRIVATE_KEY = "RSAPrivateKey";
/**
* 用私鑰對信息生成數字簽名
*
* @param data
* 加密數據
* @param privateKey
* 私鑰
*
* @return
* @throws Exception
*/
public static String sign(byte[] data, String privateKey) throws Exception {
// 解密由base64編碼的私鑰
byte[] keyBytes = decryptBASE64(privateKey);
// 構造PKCS8EncodedKeySpec對象
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
// KEY_ALGORITHM 指定的加密算法
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
// 取私鑰匙對象
PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);
// 用私鑰對信息生成數字簽名
Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
signature.initSign(priKey);
signature.update(data);
return encryptBASE64(signature.sign());
}
/**
* 校驗數字簽名
*
* @param data
* 加密數據
* @param publicKey
* 公鑰
* @param sign
* 數字簽名
*
* @return 校驗成功返回true 失敗返回false
* @throws Exception
*
*/
public static boolean verify(byte[] data, String publicKey, String sign)
throws Exception {
// 解密由base64編碼的公鑰
byte[] keyBytes = decryptBASE64(publicKey);
// 構造X509EncodedKeySpec對象
X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
// KEY_ALGORITHM 指定的加密算法
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
// 取公鑰匙對象
PublicKey pubKey = keyFactory.generatePublic(keySpec);
Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
signature.initVerify(pubKey);
signature.update(data);
// 驗證簽名是否正常
return signature.verify(decryptBASE64(sign));
}
/**
* 解密<br>
* 用私鑰解密
*
* @param data
* @param key
* @return
* @throws Exception
*/
public static byte[] decryptByPrivateKey(byte[] data, String key)
throws Exception {
// 對密鑰解密
byte[] keyBytes = decryptBASE64(key);
// 取得私鑰
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
// 對數據解密
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.DECRYPT_MODE, privateKey);
return cipher.doFinal(data);
}
/**
* 解密<br>
* 用公鑰解密
*
* @param data
* @param key
* @return
* @throws Exception
*/
public static byte[] decryptByPublicKey(byte[] data, String key)
throws Exception {
// 對密鑰解密
byte[] keyBytes = decryptBASE64(key);
// 取得公鑰
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
Key publicKey = keyFactory.generatePublic(x509KeySpec);
// 對數據解密
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.DECRYPT_MODE, publicKey);
return cipher.doFinal(data);
}
/**
* 加密<br>
* 用公鑰加密
*
* @param data
* @param key
* @return
* @throws Exception
*/
public static byte[] encryptByPublicKey(byte[] data, String key)
throws Exception {
// 對公鑰解密
byte[] keyBytes = decryptBASE64(key);
// 取得公鑰
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
Key publicKey = keyFactory.generatePublic(x509KeySpec);
// 對數據加密
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
return cipher.doFinal(data);
}
/**
* 加密<br>
* 用私鑰加密
*
* @param data
* @param key
* @return
* @throws Exception
*/
public static byte[] encryptByPrivateKey(byte[] data, String key)
throws Exception {
// 對密鑰解密
byte[] keyBytes = decryptBASE64(key);
// 取得私鑰
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
// 對數據加密
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.ENCRYPT_MODE, privateKey);
return cipher.doFinal(data);
}
/**
* 取得私鑰
*
* @param keyMap
* @return
* @throws Exception
*/
public static String getPrivateKey(Map<String, Object> keyMap)
throws Exception {
Key key = (Key) keyMap.get(PRIVATE_KEY);
return encryptBASE64(key.getEncoded());
}
/**
* 取得公鑰
*
* @param keyMap
* @return
* @throws Exception
*/
public static String getPublicKey(Map<String, Object> keyMap)
throws Exception {
Key key = (Key) keyMap.get(PUBLIC_KEY);
return encryptBASE64(key.getEncoded());
}
/**
* 初始化密鑰
*
* @return
* @throws Exception
*/
public static Map<String, Object> initKey() throws Exception {
KeyPairGenerator keyPairGen = KeyPairGenerator
.getInstance(KEY_ALGORITHM);
keyPairGen.initialize(1024);
KeyPair keyPair = keyPairGen.generateKeyPair();
// 公鑰
RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
// 私鑰
RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
Map<String, Object> keyMap = new HashMap<String, Object>(2);
keyMap.put(PUBLIC_KEY, publicKey);
keyMap.put(PRIVATE_KEY, privateKey);
return keyMap;
}
}
再來一個測試類
public class RSACoderTest {
private String publicKey;
private String privateKey;
@Before
public void setUp() throws Exception {
Map<String, Object> keyMap = RSACoder.initKey();
publicKey = RSACoder.getPublicKey(keyMap);
privateKey = RSACoder.getPrivateKey(keyMap);
System.err.println("公鑰: \n\r" + publicKey);
System.err.println("私鑰： \n\r" + privateKey);
}
@Test
public void test() throws Exception {
System.err.println("公鑰加密——私鑰解密");
String inputStr = "abc";
byte[] data = inputStr.getBytes();
byte[] encodedData = RSACoder.encryptByPublicKey(data, publicKey);
byte[] decodedData = RSACoder.decryptByPrivateKey(encodedData,
privateKey);
String outputStr = new String(decodedData);
System.err.println("加密前: " + inputStr + "\n\r" + "解密後: " + outputStr);
assertEquals(inputStr, outputStr);
}
@Test
public void testSign() throws Exception {
System.err.println("私鑰加密——公鑰解密");
String inputStr = "sign";
byte[] data = inputStr.getBytes();
byte[] encodedData = RSACoder.encryptByPrivateKey(data, privateKey);
byte[] decodedData = RSACoder
.decryptByPublicKey(encodedData, publicKey);
String outputStr = new String(decodedData);
System.err.println("加密前: " + inputStr + "\n\r" + "解密後: " + outputStr);
assertEquals(inputStr, outputStr);
System.err.println("私鑰簽名——公鑰驗證簽名");
// 產生簽名
String sign = RSACoder.sign(encodedData, privateKey);
System.err.println("簽名:\r" + sign);
// 驗證簽名
boolean status = RSACoder.verify(encodedData, publicKey, sign);
System.err.println("狀態:\r" + status);
assertTrue(status);
}
}
簡要總結一下，使用公鑰加密、私鑰解密，完成了乙方到甲方的一次數據傳遞，通過私鑰加密、公鑰解密，同時通過私鑰簽名、公鑰驗證簽名，完成了一次甲方到乙方的數據傳遞與驗證，兩次數據傳遞完成一整套的數據交互！